NATIONAL INSTRUMENTS PCI-6220 Series 16 Bit Multifunction DAQ Artisan User Manual

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YOU ARE ULTIMATELY RESPONSIBLE FOR VERIFYING AND VALIDATING THE SUITABILITY AND RELIABILITY OF THE PRODUCTS WHENEVER THE PRODUCTS ARE INCORPORATED IN YOUR SYSTEM OR APPLICATION, INCLUDING THE APPROPRIATE DESIGN, PROCESS, AND SAFETY LEVEL OF SUCH SYSTEM OR APPLICATION.
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Getting Started

The M Series User Manual contains information about using the National Instruments M Series multifunction I/O data acquisition (DAQ) devices with NI- DAQmx 15.5 and later. M Series devices feature up to 80 analog input (AI) channels, up to four analog output (AO) channels, up to 48 lines of digital input/output (DIO), and two counters. This chapter provides basic information you need to get started using your M Series device.
Safety Guidelines
Operate the NI 62xx M Series devices and modules only as described in this user manual.
Caution NI 62xx devices and modules are not certified for use in hazardous locations.
Caution Never connect the +5 V power terminals to analog or digital ground or to any other voltage source on the M Series device or any other device. Doing so can damage the device and the computer. NI is not liable for damage resulting from such a connection.
Caution The maximum input voltages rating of AI signals with respect to ground (and for signal pairs in differential mode with respect to each other) are listed in the specifications document for your device. Exceeding the maximum input voltage of AI signals distorts the measurement results. Exceeding the maximum input voltage rating also can damage the device and the computer. NI is not liable for any damage resulting from such signal connections.
Caution Exceeding the maximum input voltage ratings, which are listed in the specifications document for each M Series device, can damage the DAQ device and the computer. NI is not liable for any damage resulting from such signal connections.
Caution Damage can result if these lines are driven by the sub-bus. NI is not liable for any damage resulting from improper signal connections.
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Chapter 1 Getting Started
Safety Guidelines for Hazardous Voltages
If hazardous voltages are connected to the device/module, take the following precautions. A hazardous voltage is a voltage greater than 42.4 Vpk or 60 VDC to earth ground.
Caution Ensure that hazardous voltage wiring is performed only by qualified personnel adhering to local electrical standards.
Caution Do not mix hazardous voltage circuits and human-accessible circuits on the same module.
Caution Make sure that chassis and circuits connected to the module are properly insulated from human contact.
Caution NI 62xx devices and modules provide no isolation.
Electromagnetic Compatibility Guidelines
This product was tested and complies with the regulatory requirements and limits for electromagnetic compatibility (EMC) as stated in the product specifications. These requirements and limits are designed to provide reasonable protection against harmful interference when the product is operated in its intended operational electromagnetic environment.
This product is intended for use in industrial locations. There is no guarantee that harmful interference will not occur in a particular installation, when the product is connected to a test object, or if the product is used in residential areas. To minimize the potential for the product to cause interference to radio and television reception or to experience unacceptable performance degradation, install and use this product in strict accordance with the instructions in the product documentation.
Furthermore, any changes or modifications to the product not expressly approved by National Instruments could void your authority to operate it under your local regulatory rules.
Caution To ensure the specified EMC performance, product installation requires either special considerations or user-installed, add-on devices. Refer to the product installation instructions for further information.
Caution For compliance with Electromagnetic Compatibility (EMC) requirements, this product must be operated with shielded cables and accessories. If unshielded cables or accessories are used, the EMC specifications are no longer guaranteed unless all unshielded cables and/or accessories are installed in a shielded enclosure with properly designed and shielded input/output ports.
Caution This product may become more sensitive to electromagnetic disturbances in the operational environment when test leads are attached or when connected to a test object.
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Hardware Symbol Definitions

M Series User Manual

The following symbols are marked on your device or module.

Caution When this symbol is marked on a product, refer to the Safety Guidelines section for information about precautions to take.

EU Customers At the end of the product life cycle, all products must be sent to

a WEEE recycling center. For more information about WEEE recycling centers,

National Instruments WEEE initiatives, and compliance with WEEE Directive

2002/96/EC on Waste and Electronic Equipment, visit ni.com/environment/

weee.

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Installation

Before installing your multifunction I/O device, you must install the software you plan to use with the device.
1. Installing application software–Refer to the installation instructions that accompany your software.
2. Installing NI-DAQmx–The DAQ Getting Started Guide for PXI/PXI Express, DAQ Getting Started Guide for PCI/PCI Express, or DAQ Getting Started Guide for Externally Powered USB, packaged with your device or module, and also available on ni.com/ manuals, contain step-by-step instructions for installing software and hardware, configuring channels and tasks, and getting started developing an application.
3. Installing the hardware–Unpack your M Series device as described in the Unpacking section. Refer to the DAQ Getting Started Guide for PXI/PXI Express, DAQ Getting Started Guide for PCI/PCI Express, or DAQ Getting Started Guide for Externally Powered USB for information how to install your software and device or module. It also describes how to confirm that your device or module is operating properly, configure your device or module, run test panels, and take a measurement.
Unpacking

The M Series device ships in an antistatic package to prevent electrostatic discharge (ESD). ESD can damage several components on the device.

Caution Never touch the exposed pins of connectors.

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Chapter 1 Getting Started
To avoid ESD damage in handling the device, take the following precautions: · Ground yourself with a grounding strap or by touching a grounded object. · Touch the antistatic package to a metal part of your computer chassis before removing the
device from the package.
Remove the device from the package and inspect it for loose components or any other signs of damage. Notify NI if the device appears damaged in any way. Do not install a damaged device in your computer or chassis.
Store the device in the antistatic package when the device is not in use.
Device Self-Calibration
NI recommends that you self-calibrate your M Series device after installation and whenever the ambient temperature changes. Self-calibration should be performed after the device has warmed up for the recommended time period. Refer to the device specifications to find your device warm-up time. This function measures the onboard reference voltage of the device and adjusts the self-calibration constants to account for any errors caused by short-term fluctuations in the environment. Disconnect all external signals when you self-calibrate a device.
Note (NI PCIe-6251/6259 Devices) Connecting or disconnecting the disk drive power connector on M Series PCI Express devices can affect the analog performance of your device. To compensate for this, NI recommends that you self-calibrate after connecting or disconnecting the disk drive power connector, as described in the Device Self-Calibration section.
You can initiate self-calibration using Measurement & Automation Explorer (MAX), by completing the following steps. 1. Launch MAX. 2. Select My System»Devices and Interfaces»your device. 3. Initiate self-calibration using one of the following methods:
· Click Self-Calibrate in the upper right corner of MAX. · Right-click the name of the device in the MAX configuration tree and select
Self-Calibrate from the drop-down menu.
Note You can also programmatically self-calibrate your device with NI-DAQmx, as described in Device Calibration in the NI-DAQmx Help or the LabVIEW Help.
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M Series User Manual
Getting Started with M Series PCI Express Devices and the Disk Drive Power Connector
(NI PCIe-6251/6259 Devices) The disk drive power connector is a four-pin hard drive connector on PCI Express devices that, when connected, increases the current the device can supply on the +5 V terminal.
When to Use the Disk Drive Power Connector
M Series PCI Express devices without the disk drive power connector installed perform identically to other M Series devices for most applications and with most accessories. For most applications, it is not necessary to install the disk drive power connector.
However, you should install the disk drive power connector in either of the following situations: · You need more power than listed in the device specifications · You are using an SCC accessory without an external power supply, such as the SC-2345
Refer to the specifications document for your device for more information about PCI Express power requirements and power limits.
Disk Drive Power Connector Installation
Before installing the disk drive power connector, you must install and set up the M Series PCI Express device as described in the DAQ Getting Started Guide for PCI/PCI Express. Complete the following steps to install the disk drive power connector. 1. Power off and unplug the computer. 2. Remove the computer cover. 3. Attach the PC disk drive power connector to the disk drive power connector on the device,
as shown in Figure 1-1.
Note The power available on the disk drive power connectors in a computer can vary. For example, consider using a disk drive power connector that is not in the same power chain as the hard drive.
Figure 1-1. Connecting to the Disk Drive Power Connector

2 1

1 Device Disk Drive Power Connector

2 PC Disk Drive Power Connector © National Instruments | 1-5

Chapter 1 Getting Started
4. Replace the computer cover, and plug in and power on the computer. 5. Self-calibrate the PCI Express DAQ device in MAX by following the instructions in the
Device Self-Calibration section. Note Connecting or disconnecting the disk drive power connector can affect the analog performance of your device. To compensate for this, NI recommends that you self-calibrate after connecting or disconnecting the disk drive power connector, as described in the Device Self- Calibration section.
Getting Started with M Series USB Devices
The following sections contain information about M Series USB device features and best practices.
Applying the Signal Label to USB Screw Terminal Devices
(USB-622x/625x/628x Screw Terminal Devices) The supplied signal label can be adhered to the inside cover of the USB-62xx Screw Terminal device with supplied velcro strips as shown in Figure 1-2.
Figure 1-2. Applying the USB-62xx Screw Terminal Signal Label
USB Device Chassis Ground
(USB-622x/625x/628x Devices) For EMC compliance, the chassis of the USB M Series device must be connected to earth ground through the chassis ground. The wire should be AWG 16 or larger solid copper wire with a maximum length of 1.5 m (5 ft). Attach the wire to the earth ground of the facility’s power system. For more information about earth ground connections, refer to the KnowledgeBase document, Earth Grounding for Test and Measurement Devices, by going to ni.com/info and entering the Info Code earthground.
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M Series User Manual
You can attach a wire to the ground lug screw of any USB-62xx device, as shown in Figure 1-3. Figure 1-3. Grounding a USB-62xx Device through the Ground Lug Screw

NATIONAL INSTRUMENTS

ON

OFF

ACTIVE READY

NI USB-62xx
Multifunction I/O with Correlated Digital I/O for USB

(USB-6225/625x/628x Screw Terminal Devices) You can attach and solder a wire to the chassis ground lug of certain USB-62xx Screw Terminal devices, as shown in Figure 1-4. The wire should be as short as possible.
Figure 1-4. Grounding a USB-62xx Screw Terminal Device through the Chassis Ground Lug

(USB-62xx BNC Devices) You can attach a wire to a CHS GND screw terminal of any USB-62xx BNC device, as shown in Figure 1-5. Use as short a wire as possible. In addition, the wires in the shielded cable that extend beyond the shield should be as short as possible.
Figure 1-5. Grounding a USB-62xx BNC Device through the CHS GND Screw Terminal

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Chapter 1 Getting Started
USB Device Panel/Wall Mounting
(USB-622x/625x/628x Devices) The Externally Powered USB M Series Panel Mounting Kit (part number 780214-01, not included in your USB-62xx kit) is an accessory you can use to mount the USB-62xx family of products to a panel or wall.
USB Device LEDs
(USB-622x/625x/628x Devices) Refer to the LED Patterns section of Chapter 3, Connector and LED Information, for information about the M Series USB device LEDs.
USB Cable Strain Relief
(USB-622x/625x/628x Screw Terminal and USB-622x/625x/628x Mass Termination Devices) Use the supplied strain relief hardware to provide strain relief for your USB cable. Adhere the cable tie mount to the rear panel of the USB-62xx Screw Terminal or USB-62xx Mass Termination device, as shown in Figure 1-6. Thread a zip tie through the cable tie mount and tighten around the USB cable.
Figure 1-6. USB Cable Strain Relief on USB-62xx Screw Terminal and USB-62xx Mass Termination Devices
(USB-622x/625x BNC Devices) Thread a zip tie through two of the strain relief holes on the end cap to provide strain relief for your USB cable as shown in Figure 1-7. The strain relief holes can also be used as cable management for signal wires to/from the screw terminals and BNC connectors.
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M Series User Manual
Figure 1-7. USB Cable Strain Relief on USB-62xx BNC Devices
3

12
1 USB Cable Strain Relief 2 Security Cable Slot

3 Signal Wire Strain Relief

USB Device Fuse Replacement
M Series USB devices have a replaceable T 2A 250V (5 × 20 mm) fuse that protects the device from overcurrent through the power connector.

(USB-6281/6289 Devices) USB-628x devices also have a replaceable Littelfuse 0453002 (F 2A 250V) fuse that protects the device from overcurrent through the +5 V terminal(s).

(USB-622x/625x/628x Screw Terminal Devices) To replace a broken fuse in the USB-62xx Screw Terminal, complete the following steps. 1. Power down and unplug the device. 2. Remove the USB cable and all signal wires from the device. 3. Loosen the four Phillips screws that attach the back lid to the enclosure and remove the lid. 4. Replace the broken fuse while referring to Figure 1-8 for the fuse locations.

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Chapter 1 Getting Started
Figure 1-8. USB-62xx Screw Terminal Fuse Locations
1 2

1 T 2A 250V (5 × 20 mm) Fuse

2 Littelfuse 0453002 Fuse on USB-628x Devices

5. Replace the lid and screws.

(USB-622x/625x BNC Devices) To replace a broken fuse in the USB-62xx BNC, complete the following steps.
1. Power down and unplug the device.

Note Take proper ESD precautions when handling the device.

2. Remove the USB cable and all BNC cables and signal wires from the device.

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Figure 1-9. USB-62xx BNC Fuse Location

M Series User Manual

1 1 T 2A 250V (5 × 20 mm) Fuse
3. Remove both end pieces by unscrewing the four sockethead cap screws with a 7/64 in. hex wrench. Note The end pieces are attached using self-threading screws. Repeated screwing and unscrewing of self-threading screws will produce a compromised connection.
4. With a Phillips #2 screwdriver, remove the Phillips 4-40 screw adjacent to the USB connector.
5. Remove the nut from the power connector. 6. Remove the four Phillips 4-40 screws that attach the top panel to the enclosure and remove
the panel and connector unit. 7. Replace the broken fuse while referring to Figure 1-9 for the fuse location. 8. Replace the top panel, screws, nut, and end pieces.
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Chapter 1 Getting Started
(USB-622x/625x/628x Mass Termination Devices) To replace a broken fuse in the USB-62xx Mass Termination, complete the following steps. 1. Power down and unplug the device. 2. Remove the USB cable and signal cable(s) from the device. 3. Loosen the four Phillips screws that attach the lid to the enclosure and remove the lid. 4. Replace the broken fuse while referring to Figure 1-10 for the fuse locations.
Figure 1-10. USB-62xx Mass Termination Fuse Locations
2
1
1 T 2A 250V (5 × 20 mm) Fuse 2 Littelfuse 0453002 Fuse on USB-628x Devices
5. Replace the lid and screws.
USB Device Security Cable Slot
(USB-622x/625x BNC Devices) The security cable slot, shown in Figure 1-7, allows you to attach an optional antitheft device to your USB device.
Note The security cable is designed to act as a deterrent, but may not prevent the device from being mishandled or stolen. For more information, refer to the documentation that accompanied the security cable. Note The security cable slot on the USB-62xx BNC may not be compatible with all antitheft cables.
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M Series User Manual
Installing a Ferrite
(USB-62221/6229 BNC Devices) To ensure EMC compliance, you must install the ferrite shipped with the USB-6221/6229 BNC.
Loop the power cabling through the ferrite at least five times. Install the ferrite as close as possible to the end of the power cable, as shown in Figure 1-11.
Figure 1-11. Installing the Ferrite on the Power Cable
3

2 1

1 Power Cable 2 Ferrite
Pinouts

3 NI USB-6221/6229 BNC Device

Refer to Appendix A, Module/Device-Specific Information, for M Series device pinouts.

Specifications

Refer to the device specifications document for your device. M Series device documentation is available on ni.com/manuals.

Accessories and Cables

NI offers a variety of accessories and cables to use with your multifunction I/O DAQ module device. Refer to the Cables and Accessories section of Chapter 2, DAQ System Overview, for more information.

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2
DAQ System Overview
Figure 2-1 shows a typical DAQ system, which includes sensors, transducers, signal conditioning devices, cables that connect the various devices to the accessories, the M Series device, programming software, and PC. The following sections cover the components of a typical DAQ system.
Figure 2-1. Components of a Typical DAQ System

Sensors and Transducers

Signal Conditioning

Cables and Accessories

DAQ Hardware

DAQ Software

Personal Computer or
PXI/PXI Express Chassis

DAQ Hardware

DAQ hardware digitizes signals, performs D/A conversions to generate analog output signals, and measures and controls digital I/O signals. Figure 2-2 features components common to all M Series devices.
Figure 2-2. General M Series Block Diagram

Analog Input

I/O Connector

Analog Output Digital I/O Counters PFI

Digital

Routing and Clock

Bus Interface

Bus

Generation

RTSI

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Chapter 2

DAQ System Overview

DAQ-STC2 and DAQ-6202
The DAQ-STC2 and DAQ-6202 implement a high-performance digital engine for M Series data acquisition hardware. Some key features of this engine include the following: · Flexible AI and AO sample and convert timing · Many triggering modes · Independent AI, AO, DI, and DO FIFOs · Generation and routing of RTSI signals for multi-device synchronization · Generation and routing of internal and external timing signals · Two flexible 32-bit counter/timer modules with hardware gating · Digital waveform acquisition and generation · Static DIO signals · True 5 V high current drive DO · DI change detection · PLL for clock synchronization · Seamless interface to signal conditioning accessories · PCI/PXI interface · Independent scatter-gather DMA controllers for all acquisition and generation functions
Calibration Circuitry
The M Series analog inputs and outputs have calibration circuitry to correct gain and offset errors. You can calibrate the device to minimize AI and AO errors caused by time and temperature drift at run time. No external circuitry is necessary; an internal reference ensures high accuracy and stability over time and temperature changes.
Factory-calibration constants are permanently stored in an onboard EEPROM and cannot be modified. When you self-calibrate the device, as described in the Device Self-Calibration section of Chapter 1, Getting Started, software stores new constants in a user-modifiable section of the EEPROM. To return a device to its initial factory calibration settings, software can copy the factory- calibration constants to the user-modifiable section of the EEPROM. Refer to the NI-DAQmx Help or the LabVIEW Help for more information about using calibration constants. For a detailed calibration procedure for M Series devices, refer to the B/E/M/S/X Series Calibration Procedure available at ni.com/manuals.
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Cables and Accessories

M Series User Manual

NI offers a variety of products to use with M Series PCI, PCI Express, PXI, PXI Express, USB devices, including cables, connector blocks, and other accessories, as follows:
· Shielded cables and cable assemblies, and unshielded ribbon cables and cable assemblies
· Screw terminal connector blocks, shielded and unshielded
· RTSI bus cables
· SCXI modules and accessories for isolating, amplifying, exciting, and multiplexing signals; with SCXI you can condition and acquire up to 3,072 channels
· Low-channel-count signal conditioning modules, devices, and accessories, including conditioning for strain gauges and RTDs, simultaneous sample and hold circuitry, and relays
Refer to the appropriate section for your device connector type–68-Pin M Series Cables and Accessories or 37-Pin M Series Cables and Accessories. For more specific information about these products, refer to ni.com.

Note For compliance with Electromagnetic Compatibility (EMC) requirements, this product must be operated with shielded cables and accessories. If unshielded cables or accessories are used, the EMC specifications are no longer guaranteed unless all unshielded cables and/or accessories are installed in a shielded enclosure with properly designed and shielded input/output ports.

Refer to the 68-Pin Custom Cabling and Connectivity or 37-Pin Custom Cabling section of this chapter and the Field Wiring Considerations section of Chapter 4, Analog Input, for information about how to select accessories for your M Series device.
68-Pin M Series Cables and Accessories
This section describes some cable and accessory options for M Series devices with one or two 68-pin connectors. Refer to the following sections for descriptions of these cables and accessories. Refer to ni.com for other accessory options.

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Chapter 2 DAQ System Overview

Table 2-1. 68-Pin M Series Device/Module Cables and Accessories

Cables

Unshielded

Cables and Accessories Type
Shielded Unshielded
Screw Terminal Block
BNC Terminal Block
SCC
Screw Terminal Block

PCI, PCI Express, PXI, PXI Express Devices and Modules

622x/625x/ 628x
Connector 0
6224/6229/ 6254/6259/ 6284/6289 Connector 1

6225/6255 Connector 1

SHC68-68-EPM SHC68-68

RC68-68

RC68-68

SCB-68A SCB-68 TB-2706*

SCB-68A SCB-68

BNC-2110 BNC-2111 BNC-2120 BNC-2090A BNC-2090

BNC-2115

SC-2345

N/A

SC-2350

SCC-68

CB-68LP CB-68LPR TBX-68

CB-68LP CB-68LPR TBX-68

USB Mass Termination Devices

622x/625x/ 628x
Connector 0 6229/6259/
6289 Connector 1
SC68-68-EPM
RC68-68
SCB-68A
SCB-68

6225/6255 Connector 1
SHC68-68
RC68-68
SCB-68A SCB-68

BNC-2110 BNC-2111 BNC-2120 BNC-2090A BNC-2090
SC-2345 SC-2350 SCC-68
CB-68LP CB-68LPR TBX-68

BNC-2115
N/A
CB-68LP CB-68LPR TBX-68

Accessories Shielded

Custom Connectivity CA-1000

CA-1000

CA-1000

CA-1000

• Can only be attached directly to PXI modules front connector only, and does not require a cable.

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M Series User Manual
68-Pin Cables
Cabling options differ between the 68-pin PCI/PCI Express/PXI/PXI Express devices and modules and USB Mass Termination devices.
PCI/PCI Express/PXI/PXI Express Device/Module 68-Pin Cables You can use the following cables with PCI, PCI Express, PXI, and PXI Express M Series devices and modules: · SHC68-68-EPM1–(Recommended) High-performance shielded cable designed for
M/X Series devices. It has individual bundles separating analog and digital signals. Each differential analog input channel is routed on an individually shielded twisted pair of wires. Analog outputs are also individually shielded. · SHC68-68–(Recommended) Lower-cost shielded cable with 34 twisted pairs of wire. The cable is recommended for PCI/PXI-6225/6255 Connector 1.
Note You must use the SHC68-68 cable on Connector 1 of PCI/PXI-6225/6255 devices and modules. The SHC68-68-EPM cable can be used on Connector 0 of all M Series PCI, PCI Express, PXI, and PXI Express devices and modules, and on Connector 1 of NI PCI/PCIe/PXI/PXI-6224/6229/6254/6259/6284/6289 devices and modules.
· RC68-68–Highly-flexible unshielded ribbon cable.
USB Mass Termination Device 68-Pin Cables You can use the following cables with USB devices with mass termination connectors: · SH68-68-EPM2–(Recommended) High-performance cable with individual bundles
separating analog and digital signals. Each differential analog input channel is routed on an individually shielded twisted pair of wires. Analog outputs are also individually shielded. · SH68-68-S–(Recommended) Shielded cable with 34 twisted pairs of wire. Each differential analog input channel on Connector 1 is routed on a twisted pair on the SH68-68-S cable. The cable is recommended for USB-6225/6255 Mass Termination Connector 1.
Note You must use the SH68-68-S cable on Connector 1 of USB-6225/6255 Mass Termination devices. The SH68-68-EPM cable can be used on Connector 0 of all M Series USB Mass Termination devices, and on Connector 1 of USB-6229/6259/6289 devices and modules.
· R68-68–Highly-flexible unshielded ribbon cable.
1 NI recommends that you use the SHC68-68-EPM cable; however, an SHC68-68-EP cable works with PCI/PCI Express/PXI/PXI Express devices and modules.
2 NI recommends that you use the SH68-68-EPM cable; however, an SH68-68-EP cable will work with USB Mass Termination devices.
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Chapter 2 DAQ System Overview
68-Pin BNC Accessories
You can use your 68-pin cable to connect your DAQ device to the following BNC accessories: · BNC-2110–Provides BNC connectivity to all analog signals, some digital signals, and
spring terminals for other digital signals · BNC-2111–Provides BNC connectivity to 16 single-ended analog input signals,
two analog output signals, five DIO/PFI signals, and the external reference voltage for analog output · BNC-2120–Similar to the BNC-2110, and also has a built-in function generator, quadrature encoder, temperature reference, and thermocouple connector · BNC-2090A, BNC-2090–Desktop/rack-mountable device with 22 BNCs for connecting analog, digital, and timing signals · BNC-2115–(NI 6225/6255 Devices) Provides BNC connectivity to 24 of the differential (48 single ended) analog input signals on Connector 1 of NI 6225/6255 devices
68-Pin Screw Terminal Accessories
You can use your 68-pin cable to connect your DAQ device to the following screw terminal accessories: · SCB-68A, SCB-68–Shielded connector block with temperature sensor · TB-27061–Front panel mounted terminal block for PXI/PXI Express M Series devices · SCC-68–I/O connector block with screw terminals, general breadboard area, bus
terminals, and four expansion slots for SCC signal conditioning modules. · TBX-68–DIN rail-mountable connector block · CB-68LP, CB-68LPR–Unshielded connector blocks
RTSI Cables
Use RTSI bus cables to connect timing and synchronization signals among PCI/PCI Express devices, such as X Series, E Series, CAN, and other measurement, vision, and motion devices. Since PXI devices use PXI backplane signals for timing and synchronization, no cables are required.
SCC Carriers and Accessories
SCC provides portable, modular signal conditioning to your DAQ system. Use your 68-pin cable to connect your device/module to an SCC module carrier, such as the following: · SCC-68–68-pin terminal block with SCC expansion slots · SC-2345–Shielded carrier for up to 20 SCC modules · SC-2350–Shielded SCC carrier for TEDS sensors
1 TB-2706 uses Connector 0 of your PXI/PXI Express module, therefore does not require a cable. After a TB-2706 is installed, Connector 1 cannot be used.
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M Series User Manual
You can use either connector on M Series devices to control an SCC module carrier.
Note (NI 6225/6255 Devices) SCC is supported only on Connector 0.
Note PCI Express users should consider the power limits on certain SCC modules without an external power supply. Refer to the device specifications, and the When to Use the Disk Drive Power Connector section of Chapter 1, Getting Started, for information about power limits and increasing the current the device can supply on the +5 V terminal.
SCXI
SCXI is a programmable signal conditioning system designed for measurement and automation applications. To connect your M Series device or module to an SCXI chassis, use the SCXI-1349 adapter and your 68-pin cable.
Use Connector 0 of your M Series device to control SCXI in parallel and multiplexed mode. Use Connector 1 of your M Series device to control SCXI in parallel mode.
Note (NI 6225/6255 Devices) SCXI is supported only on Connector 0.
Note When using Connector 1 in parallel mode with SCXI modules that support track and hold, you must programmatically disable track and hold.
You also can use an M Series PXI module to control the SCXI section of a PXI/SCXI combination chassis, such as the PXI-1010 or PXI-1011. The M Series device in the rightmost PXI slot controls the SCXI devices. No cables or adapters are necessary.
Refer to the documentation for your SCXI chassis and modules for detailed information about using SCXI with a DAQ device.
68-Pin Custom Cabling and Connectivity
The CA-1000 is a configurable enclosure that gives user-defined connectivity and flexibility through customized panelettes. Visit ni.com for more information about the CA-1000.
NI offers cables and accessories for many applications. However, if you want to develop your own cable, adhere to the following guidelines for best results: · For AI signals, use shielded, twisted-pair wires for each AI pair of differential inputs.
Connect the shield for each signal pair to the ground reference at the source. · Route the analog lines separately from the digital lines. · When using a cable shield, use separate shields for the analog and digital sections of the
cable. To prevent noise when using a cable shield, use separate shields for the analog and digital sections of the cable.
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Chapter 2 DAQ System Overview

For more information on the connectors used for DAQ devices, refer to the NI DAQ Device Custom Cables, Replacement Connectors, and Screws document by going to ni.com/info and entering the Info Code rdspmb.

USB Device Accessories, USB Cable, and Power Supply
USB Screw Terminal and USB Mass Termination devices feature connectivity directly on the device and do not require an accessory for interfacing to signals. However, NI offers a variety of products to use with the USB M Series devices, as shown in Table 2-2.

Table 2-2. USB Device Cabling, Accessories, and Power Supply

Description NI USB DAQ Power Supply Externally Powered USB M Series Panel Mounting Kit USB cable with locking screw, 2 m BNC Male (Plug) to BNC Male (Plug) Cable Not for use with NI USB BNC devices.

Part Number 780046-01 780214-01
780534-01 779697-02

37-Pin M Series Cables and Accessories
This section describes some cable and accessory options for the PCI-6221 (37-pin) device. Refer to the following sections for descriptions of these cables and accessories. Refer to ni.com for other accessory options.

Table 2-3. PCI-6221 (37-Pin) Cables and Accessories

Cables

Cables and Accessories Type
Shielded

Accessories

Unshielded Unshielded Screw Terminal Block

Custom Connectivity

Supported Models for PCI-6221 (37-Pin) Device
SH37F-37M SH37F-P-4 R37F-37M CB-37F-HVD CB-37FV CB-37FH CB-37F-LP TB-37F-37SC TB-37F-37CP

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M Series User Manual
37-Pin Cables
In most applications, you can use the following cables: · SH37F- 37M–(Recommended) 37-pin female-to-male shielded I/O cable,
(1 m and 2 m lengths) · SH37F-P-4–37-pin female-to-pigtails shielded I/O cable · R37F-37M–37-pin female-to-male ribbon I/O cable
37-Pin Screw Terminal Accessories
National Instruments offers several styles of screw terminal connector blocks. Use your 37-pin cable to connect a PCI-6221 (37-pin) device to one of the following connector blocks: · CB-37F-HVD–37-pin DIN rail screw terminal block · CB-37FV–Vertical DIN rail-mountable terminal block with 37 screw terminals · CB-37FH–Horizontal DIN rail-mountable connector block with 37 screw terminals · CB-37F-LP–Low profile connector block with 37 screw terminals
RTSI Cables
Use RTSI bus cables to connect timing and synchronization signals among PCI/PCI Express devices, such as X Series, E Series, CAN, and other measurement, vision, and motion devices. Since PXI devices use PXI backplane signals for timing and synchronization, no cables are required.
37-Pin Custom Cabling
NI offers cables and accessories for many applications. However, if you want to develop your own cable, the following kits can assist you: · TB-37F- 37SC–37-pin solder cup terminals, shell with strain relief · TB-37F- 37CP–37-pin crimp & poke terminals, shell with strain relief
Adhere to the following guidelines for best results: · For AI signals, use shielded, twisted-pair wires for each AI pair of differential inputs.
Connect the shield for each signal pair to the ground reference at the source. · Route the analog lines separately from the digital lines. · When using a cable shield, use separate shields for the analog and digital sections of the
cable. Failure to do so results in noise coupling into the analog signals from transient digital signals.
For more information on the connectors used for DAQ devices, refer to the NI DAQ Device Custom Cables, Replacement Connectors, and Screws document by going to ni.com/info and entering the Info Code rdspmb.
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Chapter 2 DAQ System Overview
Signal Conditioning
Many sensors and transducers require signal conditioning before a measurement system can effectively and accurately acquire the signal. The front-end signal conditioning system can include functions such as signal amplification, attenuation, filtering, electrical isolation, simultaneous sampling, and multiplexing. In addition, many transducers require excitation currents or voltages, bridge completion, linearization, or high amplification for proper and accurate operation. Therefore, most computer-based measurement systems include some form of signal conditioning in addition to plug-in data acquisition DAQ devices.
Sensors and Transducers
Sensors can generate electrical signals to measure physical phenomena, such as temperature, force, sound, or light. Some commonly used sensors are strain gauges, thermocouples, thermistors, angular encoders, linear encoders, and resistance temperature detectors (RTDs).
To measure signals from these various transducers, you must convert them into a form that a DAQ device can accept. For example, the output voltage of most thermocouples is very small and susceptible to noise. Therefore, you may need to amplify or filter the thermocouple output before digitizing it. The manipulation of signals to prepare them for digitizing is called signal conditioning.
For more information about sensors, refer to the following documents: · For general information about sensors, visit ni.com/sensors. · If you are using LabVIEW, refer to the LabVIEW Help by selecting Help»Search the
LabVIEW Help in LabVIEW and then navigate to the Taking Measurements book on the Contents tab. · If you are using other application software, refer to Common Sensors in the NI-DAQmx Help or the LabVIEW Help.
Signal Conditioning Options
For more information about SCXI and SCC products, refer to ni.com/ signalconditioning.
SCXI
SCXI is a front-end signal conditioning and switching system for various measurement devices, including M Series devices. An SCXI system consists of a rugged chassis that houses shielded signal conditioning modules that amplify, filter, isolate, and multiplex analog signals from thermocouples or other transducers. SCXI is designed for large measurement systems or systems requiring high-speed acquisition.
System features include the following: · Modular architecture–Choose your measurement technology · Expandability–Expand your system to 3,072 channels
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M Series User Manual
· Integration–Combine analog input, analog output, digital I/O, and switching into a single, unified platform
· High bandwidth–Acquire signals at high rates · Connectivity–Select from SCXI modules with thermocouple connectors or terminal
blocks
Note SCXI is not supported on the PCI-6221 (37-pin), USB-622x/625x/628x Screw Terminal, or USB-622x/625x BNC devices.
SCC
SCC is a front-end signal conditioning system for M Series plug-in data acquisition devices. An SCC system consists of a shielded carrier that holds up to 20 single- or dual-channel SCC modules for conditioning thermocouples and other transducers. SCC is designed for small measurement systems where you need only a few channels of each signal type, or for portable applications. SCC systems also offer the most comprehensive and flexible signal connectivity options.
System features include the following: · Modular architecture–Select your measurement technology on a per-channel basis · Small-channel systems–Condition up to 16 analog input and eight digital I/O lines · Low- profile/portable–Integrates well with other laptop computer measurement
technologies · High bandwidth–Acquire signals at rates up to 1.25 MHz · Connectivity–Incorporates panelette technology to offer custom connectivity to
thermocouple, BNC, LEMOTM (B Series), and MIL-Spec connectors
Note PCI Express users should consider the power limits on certain SCC modules without an external power supply. Refer to the device specifications, and the When to Use the Disk Drive Power Connector section of Chapter 1, Getting Started, for information about power limits and increasing the current the device can supply on the +5 V terminal.
Note SCC is not supported on the PCI-6221 (37-pin), USB-622x/625x/628x Screw Terminal, or USB-622x/625x BNC devices.
Programming Devices in Software
National Instruments measurement devices are packaged with NI-DAQmx driver software, an extensive library of functions and VIs you can call from your application software, such as LabVIEW or LabWindowsTM/CVITM, to program all the features of your NI measurement devices. Driver software has an application programming interface (API), which is a library of VIs, functions, classes, attributes, and properties for creating applications for your device.
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Chapter 2 DAQ System Overview

M Series devices use the NI-DAQmx driver. NI-DAQmx includes a collection of programming examples to help you get started developing an application. You can modify example code and save it in an application. You can use examples to develop a new application or add example code to an existing application.

To locate LabVIEW, LabWindows/CVI, Measurement Studio, Visual Basic, and ANSI C examples, refer to the KnowledgeBase document, Where Can I Find NI-DAQmx Examples?, by going to ni.com/info and entering the Info Code daqmxexp.

For additional examples, refer to ni.com/examples.

Table 2-4 lists the earliest NI-DAQmx support version for each M Series device.

Table 2-4. M Series NI-DAQmx Software Support

Device NI PCI/PXI-6220/6221/6224/6229 NI PCI-6221 (37-pin) NI USB-6221/6229 Screw Terminal NI USB-6221/6229 BNC NI PCI/PXI-6225 NI USB-6225 Screw Terminal/Mass Termination NI PCI/PXI-6250/6251/6254/6259 NI PCIe-6251/6259 NI PXIe-6251/6259 NI USB-6251/6259 Screw Terminal/Mass Termination NI USB-6251/6259 BNC NI PCI/PXI-6255 NI USB-6255 Screw Terminal/Mass Termination NI PCI/PXI-6280/6281/6284/6289 NI USB-6281/6289 Screw Terminal/Mass Termination

NI-DAQmx Earliest Version Support
NI-DAQmx 7.4 NI-DAQmx 7.5 NI-DAQmx 8.3 NI-DAQmx 8.6.1 NI-DAQmx 7.4 NI-DAQmx 8.6.1 NI-DAQmx 7.4 NI-DAQmx 8.0.1 NI-DAQmx 8.3 NI-DAQmx 8.1 NI-DAQmx 8.6.1 NI- DAQmx 8.1 NI-DAQmx 8.6.1 NI-DAQmx 7.4 NI-DAQmx 8.7.1

Note NI recommends using the latest version of NI-DAQmx supported for your OS. Refer to the NI-DAQmx download page by going to ni.com/info and entering the Info Code nidaqmxdownloads.

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3
Connector and LED Information
The I/O Connector Signal Descriptions, +5 V Power Source, and USER 1 and USER 2 sections contain information about M Series connector signals, power, and user-defined terminals. The LED Patterns section contains information about M Series USB device LEDs.
Note Refer to Appendix A, Module/Device-Specific Information, for device I/O connector pinouts.
I/O Connector Signal Descriptions
Table 3-1 describes the signals found on the I/O connectors. Not all signals are available on all devices.
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Chapter 3

Connector and LED Information

Signal Name AI GND
AI <0..79>
AI SENSE, AI SENSE 2 AO <0..3> AO GND

Table 3-1. I/O Connector Signals

Reference —
Varies
— AO GND
—

Direction —
Input
Input Output
—

Description
Analog Input Ground–These terminals are the reference point for single-ended AI measurements in RSE mode and the bias current return point for DIFF measurements. All three ground references–AI GND, AO GND, and D GND–are connected on the device. Refer to the Connecting Analog Input Signals section of Chapter 4,

Analog Input

Analog Input Channels–For single-ended measurements, each signal is an analog input voltage channel. In RSE mode, AI GND is the reference for these signals. In NRSE mode, the reference for each AI <0..15> signal is AI SENSE; the reference for each AI <16..63> and AI <64..79> signal is AI SENSE 2.
For differential measurements, AI 0 and AI 8 are the positive and negative inputs of differential analog input channel 0. Similarly, the following signal pairs also form differential input channels: <AI 1, AI 9>, <AI 2, AI 10>, <AI 3, AI 11>, and so on.
Refer to the Connecting Analog Input Signals section of Chapter 4, Analog Input.
Analog Input Sense–In NRSE mode, the reference for each AI <0..15> signal is AI SENSE; the reference for each AI <16..63> and AI <64..79> signal is AI SENSE 2. Refer to the Connecting Analog Input Signals section of Chapter 4, Analog Input.
Analog Output Channels–These terminals supply the voltage output. Refer to the Connecting Analog Output Signals section of Chapter 5, Analog Output.
Analog Output Ground–AO GND is the reference for AO <0..3>. All three ground references–AI GND, AO GND, and D GND–are connected on the device. Refer to the Connecting Analog Output Signals section of Chapter 5, Analog Output.

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Signal Name D GND
P0.<0..31> APFI <0,1>
+5 V PFI <0..7>/ P1.<0..7>

M Series User Manual

Table 3-1. I/O Connector Signals (Continued)

Reference —
D GND AO GND or AI GND
D GND D GND

Direction —
Input or Output Input
Output Input or Output

Description
Digital Ground–D GND supplies the reference for P0.<0..31>, PFI <0..15>/P1/P2, and +5 V. All three ground references–AI GND, AO GND, and D GND–are connected on the device. Refer to the Connecting Digital I/O Signals section of Chapter 6, Digital I/O.
Port 0 Digital I/O Channels–You can individually configure each signal as an input or output. Refer to the Connecting Digital I/O Signals section of Chapter 6, Digital I/O.
Analog Programmable Function Interface Channels–Each APFI signal can be used as AO external reference inputs for AO <0..3>, AO external offset input, or as an analog trigger input. APFI <0,1> are referenced to AI GND when they are used as analog trigger inputs. APFI <0,1> are referenced to AO GND when they are used as AO external offset or reference inputs. These functions are not available on all devices; refer to the specifications for your device. Refer to the APFI <0,1> Terminals section of Chapter 11, Triggering.
+5 V Power Source–These terminals provide a fused +5 V power source. Refer to the +5 V Power Source section for more information.
Programmable Function Interface or Port 1 Digital I/O Channels–Each of these terminals can be individually configured as a PFI terminal or a digital I/O terminal.
As an input, each PFI terminal can be used to supply an external source for AI, AO, DI, and DO timing signals or counter/timer inputs.
As a PFI output, you can route many different internal AI, AO, DI, or DO timing signals to each PFI terminal. You also can route the counter/timer outputs to each PFI terminal.
As a Port 1 digital I/O signal, you can individually configure each signal as an input or output.
Refer to the Connecting Digital I/O Signals section of Chapter 6, Digital I/O, or to Chapter 8, PFI.

© National Instruments | 3-3

Chapter 3 Connector and LED Information

Table 3-1. I/O Connector Signals (Continued)

Signal Name

Reference Direction

Description

PFI <8..15>/ P2.<0..7>

D GND

Input or Output

Programmable Function Interface or Port 2 Digital I/O Channels–Each of these terminals can be individually configured as a PFI terminal or
a digital I/O terminal.

As an input, each PFI terminal can be used to supply an external source for AI, AO, DI, and DO timing signals or counter/timer inputs.

As a PFI output, you can route many different internal AI, AO, DI, or DO timing signals to each PFI terminal. You also can route the counter/timer outputs to each PFI terminal.

As a Port 2 digital I/O signal, you can individually configure each signal as an input or output.

Refer to the Connecting Digital I/O Signals section of Chapter 6, Digital I/O, or to Chapter 8, PFI. Refer to Table 7-6, 68-Pin Device Default NI-DAQmx Counter/Timer Pins, to find the default NI-DAQmx counter/timer pins for most
M Series devices.

USER <1,2>

—

—

User-Defined Channels–On USB-62xx BNC

devices, the USER <1,2> BNC connectors allow

you to use a BNC connector for a digital or timing

I/O signal of your choice. The USER <1,2> BNC

connectors are internally routed to the USER

<1,2> screw terminals. Refer to the USER 1 and

USER 2 section for more information.

CHS GND

—

—

Chassis Ground–This terminal connects to the

USB-62xx BNC device metal enclosure. You can

connect your cable’s shield wire to CHS GND for

a ground connection. Refer to the USB Device

Chassis Ground section of Chapter 1, Getting

Started.

NC

—

—

No connect–Do not connect signals to these

terminals.

• On NI 6225 devices, the reference for each AI <16..63> signal is AI SENSE 2, and each AI <64..79> signal is AI SENSE in NRSE mode.

USB-62xx Screw Terminal users can connect the shield of a shielded cable to the chassis ground lug for a ground connection. The chassis ground lug is not available on all device versions.

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+5 V Power Source

M Series User Manual

The +5 V terminals on the I/O connector supply +5 V referenced to D GND. Use these terminals to power external circuitry.
Newer revision M Series devices have a traditional fuse to protect the supply from overcurrent conditions. This fuse is not customer-replaceable; if the fuse permanently opens, return the device to NI for repair.
Older revision M Series devices have a self-resetting fuse to protect the supply from overcurrent conditions. This fuse resets automatically within a few seconds after the overcurrent condition is removed. For more information about the self-resetting fuse and precautions to take to avoid improper connection of +5 V and ground terminals, refer to the KnowledgeBase document, Self-Resetting Fuse Additional Information, by going to ni.com/info and entering the Info Code pptc.
(USB-6281/6289 Devices) All USB-628x devices have a user-replaceable socketed fuse to protect the supply from overcurrent conditions. When an overcurrent condition occurs, check your cabling to the +5 V terminals and replace the fuse as described in the USB Device Fuse Replacement section of Chapter 1, Getting Started.

Caution Never connect the +5 V power terminals to analog or digital ground or to any other voltage source on the M Series device or any other device. Doing so can damage the device and the computer. NI is not liable for damage resulting from such a connection.

The power rating on most devices is +4.75 to +5.25 VDC at 1 A. Refer to the specifications document for your device to obtain the device power rating.

Note (NI PCIe-6251/6259 Devices) M Series PCI Express devices supply less
than 1 A of +5 V power unless you use the disk drive power connector. Refer to the Getting Started with M Series PCI Express Devices and the Disk Drive Power Connector section of Chapter 1, Getting Started, for more information.

Note The NI 6221 (37-pin) device does not have a +5 V terminal.

USER 1 and USER 2

(NI USB-622x/625x BNC Devices) The USER connectors allow you to use a BNC connector for a digital or timing I/O signal of your choice. The USER 1 and USER 2 BNC connectors are routed (internal to the USB BNC device) to the USER 1 and USER 2 screw terminals, as shown in Figure 3-1.

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Chapter 3 Connector and LED Information
Figure 3-1. USER 1 and USER 2 BNC Connections
USER 1 BNC USER 2 BNC

USER 1 USER 2 D GND
+5 V D GND
P0.0 P0.1 P0.2 P0.3 D GND P0.4 P0.5 P0.6 P0.7 D GND PFI 8/P2.0

D GND

D GND

Internal Connection

Screw Terminal Block

Figure 3-2 shows an example of how to use the USER 1 and USER 2 BNCs. To access the PFI 8 signal from a BNC, connect USER 1 on the screw terminal block to PFI 8 with a wire.
Figure 3-2. Connecting PFI 8 to USER 1 BNC
USER 1 BNC

BNC Cable

USER 1

USER 2

D GND

+5 V

D GND

P0.0

P0.1

P0.2

PFI 8

P0.3

Signal D GND

P0.4

P0.5

P0.6

P0.7

D GND

PFI 8/P2.0

Internal D GND Connection
Wire
Screw Terminal Block

The designated space below each USER BNC is for marking or labeling signal names.
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RTSI Connector Pinout

M Series User Manual

(PCI/PCIe-622x/625x/628x Devices) Refer to the RTSI Connector Pinout section of Chapter 9, Digital Routing and Clock Generation, for information about the RTSI connector.
LED Patterns

(USB-622x/625x/628x Devices) All variants of M Series USB devices have LEDs labeled ACTIVE and READY. The ACTIVE LED indicates activity over the bus. The READY LED indicates whether or not the device is configured. Table 3-2 shows the behavior of the LEDs.

Note USB-62xx BNC devices also have a POWER (+5 V) LED on the top panel. The POWER (+5 V) LED indicates device power.

Table 3-2. LED Patterns

POWER (+5 V) LED*
Off
On

ACTIVE LED
Off
Off

READY LED
Off
Off

On

Off

On

On

On

On

On

Blinking

On

• USB-625x/628x BNC devices only.

USB Device State
The device is not powered.
(USB-62xx Screw Terminal/Mass Termination Devices) The device is not powered.
(USB-62xx BNC Devices) The device is powered but not connected to the host computer.
The device is configured, but there is no activity over the bus.
The device is configured and there is activity over the bus.

© National Instruments | 3-7

4
Analog Input

Figure 4-1 shows the analog input circuitry of M Series devices. Figure 4-1. M Series Analog Input Circuitry

I/O Connector

AI <0..207> Mux
AI SENSE

DIFF, RSE, or NRSE

NI-PGIA

ADC

AI FIFO

AI Data

AI GND

Input Range Selection
AI Terminal Configuration
Selection

The main blocks featured in the M Series analog input circuitry are as follows:
· I/O Connector–You can connect analog input signals to the M Series device through the I/O connector. The proper way to connect analog input signals depends on the analog input ground-reference settings, described in the Analog Input Ground-Reference Settings section. Also refer to Appendix A, Module /Device-Specific Information, for device I/O connector pinouts.
· Mux–Each M Series device has one analog-to-digital converter (ADC). The multiplexers (mux) route one AI channel at a time to the ADC through the NI- PGIA.
· Ground-Reference Settings–The analog input ground-reference settings circuitry selects between differential, referenced single-ended, and non- referenced single-ended input modes. Each AI channel can use a different mode.
· Instrumentation Amplifier (NI-PGIA)–The NI programmable gain instrumentation amplifier (NI-PGIA) is a measurement and instrument class amplifier that minimizes settling times for all input ranges. The NI-PGIA can amplify or attenuate an AI signal to ensure that you use the maximum resolution of the ADC.
M Series devices use the NI-PGIA to deliver high accuracy even when sampling multiple channels with small input ranges at fast rates. M Series devices can sample channels in any order at the maximum conversion rate, and you can individually program each channel in a sample with a different input range.

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Chapter 4

Analog Input

· A/D Converter–The analog-to-digital converter (ADC) digitizes the AI signal by converting the analog voltage into a digital number.
· AI FIFO–M Series devices can perform both single and multiple A/D conversions of a fixed or infinite number of samples. A large first-in-first- out (FIFO) buffer holds data during AI acquisitions to ensure that no data is lost. M Series devices can handle multiple A/D conversion operations with DMA, interrupts, or programmed I/O.
Analog Input Range
Input range refers to the set of input voltages that an analog input channel can digitize with the specified accuracy. The NI-PGIA amplifies or attenuates the AI signal depending on the input range. You can individually program the input range of each AI channel on your M Series device. The input range affects the resolution of the M Series device for an AI channel. Resolution refers to the voltage of one ADC code. For example, a 16-bit ADC converts analog inputs into one of 65,536 (= 216) codes–that is, one of 65,536 possible digital values. These values are spread fairly evenly across the input range. So, for an input range of -10 V to 10 V, the voltage of each code of a 16-bit ADC is:
1—0—-V——­—-(—­—1—0—V—–) = 305µV 216
M Series devices use a calibration method that requires some codes (typically about 5% of the codes) to lie outside of the specified range. This calibration method improves absolute accuracy, but it increases the nominal resolution of input ranges by about 5% over what the formula shown above would indicate. Choose an input range that matches the expected input range of your signal. A large input range can accommodate a large signal variation, but reduces the voltage resolution. Choosing a smaller input range improves the voltage resolution, but may result in the input signal going out of range. For more information about setting ranges, refer to the NI-DAQmx Help or the LabVIEW Help.
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M Series User Manual

Table 4-1 shows the input ranges and resolutions supported by each M Series device family.

Table 4-1. M Series Input Range and Nominal Resolution

M Series Devices NI 622x NI 625x
NI 628x

Input Range -10 V to 10 V
-5 V to 5 V -1 V to 1 V -200 mV to 200 mV -10 V to 10 V -5 V to 5 V -2 V to 2 V -1 V to 1 V -500 mV to 500 mV -200 mV to 200 mV -100 mV to 100 mV -10 V to 10 V -5 V to 5 V -2 V to 2 V -1 V to 1 V -500 mV to 500 mV -200 mV to 200 mV -100 mV to 100 mV

Nominal Resolution Assuming 5% Over Range 320 µV 160 µV 32 µV 6.4 µV 320 µV 160 µV 64 µV 32 µV 16 µV 6.4 µV 3.2 µV 80.1 µV 40.1 µV 16.0 µV 8.01 µV 4.01 µV 1.60 µV 0.80 µV

Analog Input Lowpass Filter

A lowpass filter attenuates signals with frequencies above the cutoff frequency while passing, with minimal attenuation, signals below the cutoff frequency. The cutoff frequency is defined as the frequency at which the output amplitude has decreased by 3 dB. Lowpass filters attenuate noise and reduce aliasing of signals beyond the Nyquist frequency. For example, if the signal of interest does not have frequency components beyond 40 kHz, then using a filter with a cutoff frequency at 40 kHz attenuates noise beyond the cutoff that is not of interest. The cutoff

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Chapter 4 Analog Input
frequency of the lowpass filter is also called the small signal bandwidth. The specifications document for your DAQ device lists the small signal bandwidth.
On some devices, the filter cutoff is fixed. On other devices, this filter is programmable and can be enabled for a lower frequency. For example, the NI 628x devices have a programmable filter with a cutoff frequency of 40 kHz that can be enabled. If the programmable filter is not enabled, the cutoff frequency is fixed at 750 kHz. If the cutoff is programmable, choose the lower cutoff to reduce measurement noise. However, a filter with a lower cutoff frequency increases the settling time of your device, as shown in the specifications, which reduces its maximum conversion rate. Therefore, you may have to reduce the rate of your AI Convert and AI Sample Clocks. If that reduced sample rate is too slow for your application, select the higher cutoff frequency.
Add additional filters to AI signals using external accessories, as described in the Programming Devices in Software section of Chapter 2, DAQ System Overview.
Analog Input Ground-Reference Settings
M Series devices support the analog input ground-reference settings: · Differential mode–In DIFF mode, the M Series device measures the difference in voltage
between two AI signals. · Referenced single-ended mode–In RSE mode, the M Series device measures the voltage
of an AI signal relative to AI GND. · Non-referenced single-ended mode–In NRSE mode, the M Series device measures the
voltage of an AI signal relative to one of the AI SENSE or AI SENSE 2 inputs.
The AI ground-reference setting determines how you should connect your AI signals to the M Series device. Refer to the Connecting Analog Input Signals section for more information.
Ground-reference settings are programmed on a per-channel basis. For example, you might configure the device to scan 12 channels–four differentially- configured channels and eight single-ended channels.
M Series devices implement the different analog input ground-reference settings by routing different signals to the NI-PGIA. The NI-PGIA is a differential amplifier. That is, the NI-PGIA amplifies (or attenuates) the difference in voltage between its two inputs. The NI-PGIA drives the ADC with this amplified voltage. The amount of amplification (the gain), is determined by the analog input range, as shown in Figure 4-2.
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M Series User Manual

Figure 4-2. NI-PGIA

Instrumentation Amplifier

Vin+

PGIA

Vin­

Vm

Measured Voltage

­

Vm = [Vin+ ­ Vin­] × Gain
Table 4-2 shows how signals are routed to the NI-PGIA.

Table 4-2. Signals Routed to the NI-PGIA

AI Ground-Reference
Settings
RSE

Signals Routed to the Positive Input of the
NI-PGIA (Vin+)
AI <0..79>

Signals Routed to the Negative Input of the
NI-PGIA (Vin-)
AI GND

NRSE

AI <0..15>

AI SENSE

AI <16..79>

AI SENSE 2*

DIFF

AI <0..7>

AI <8..15>

AI <16..23>

AI <24..31>

AI <32..39>

AI <40..47>

AI <48..55>

AI <56..63>

AI <64..71>

AI <72..79>

• On NI 6225 devices, the reference for each AI <16..63> signal is AI SENSE 2, and each AI <64..79> signal is AI SENSE in NRSE mode.

For differential measurements, AI 0 and AI 8 are the positive and negative inputs of differential analog input channel 0. For a complete list of signal pairs that form differential input channels, refer to the pinout diagram for your device in Appendix A, Module/Device-Specific Information.
Caution The maximum input voltages rating of AI signals with respect to ground (and for signal pairs in differential mode with respect to each other) are listed in the specifications document for your device. Exceeding the maximum input voltage of AI signals distorts the measurement results. Exceeding the maximum input voltage rating also can damage the device and the computer. NI is not liable for any damage resulting from such signal connections.

© National Instruments | 4-5

Chapter 4 Analog Input
AI ground-reference setting is sometimes referred to as AI terminal configuration.
Configuring AI Ground-Reference Settings in Software
You can program channels on an M Series device to acquire with different ground references.
To enable multimode scanning in LabVIEW, use the NI-DAQmx Create Virtual Channel VI of the NI-DAQmx API. You must use a new VI for each channel or group of channels configured in a different input mode. In Figure 4-3, channel 0 is configured in differential mode, and channel 1 is configured in referenced single-ended mode.
Figure 4-3. Enabling Multimode Scanning in LabVIEW
To configure the input mode of your voltage measurement using the DAQ Assistant, use the Terminal Configuration drop-down list. Refer to the DAQ Assistant Help for more information about the DAQ Assistant.
To configure the input mode of your voltage measurement using the NI-DAQmx C API, set the terminalConfig property. Refer to the NI-DAQmx C Reference Help for more information.
Multichannel Scanning Considerations
M Series devices can scan multiple channels at high rates and digitize the signals accurately. However, you should consider several issues when designing your measurement system to ensure the high accuracy of your measurements.
In multichannel scanning applications, accuracy is affected by settling time. When your M Series device switches from one AI channel to another AI channel, the device configures the NI-PGIA with the input range of the new channel. The NI-PGIA then amplifies the input signal with the gain for the new input range. Settling time refers to the time it takes the NI-PGIA to amplify the input signal to the desired accuracy before it is sampled by the ADC. The specifications document for your DAQ device lists its settling time.
M Series devices are designed to have fast settling times. However, several factors can increase the settling time which decreases the accuracy of your measurements. To ensure fast settling times, you should do the following (in order of importance): 1. Use Low Impedance Sources–To ensure fast settling times, your signal sources should
have an impedance of <1 k. Large source impedances increase the settling time of the NI-PGIA, and so decrease the accuracy at fast scanning rates.
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M Series User Manual
Settling times increase when scanning high-impedance signals due to a phenomenon called charge injection. Multiplexers contain switches, usually made of switched capacitors. When one of the channels, for example channel 0, is selected in a multiplexer, those capacitors accumulate charge. When the next channel, for example channel 1, is selected, the accumulated charge leaks backward through channel 1. If the output impedance of the source connected to channel 1 is high enough, the resulting reading of channel 1 can be partially affected by the voltage on channel 0. This effect is referred to as ghosting. If your source impedance is high, you can decrease the scan rate to allow the NI-PGIA more time to settle. Another option is to use a voltage follower circuit external to your DAQ device to decrease the impedance seen by the DAQ device. Refer to the KnowledgeBase document, Decreasing the Source Impedance of an Analog Input Signal, by going to ni.com/info and entering the Info Code rdbbis. 2. Use Short High-Quality Cabling–Using short high-quality cables can minimize several effects that degrade accuracy including crosstalk, transmission line effects, and noise. The capacitance of the cable also can increase the settling time. National Instruments recommends using individually shielded, twisted-pair wires that are 2 m or less to connect AI signals to the device. Refer to the Connecting Analog Input Signals section for more information. 3. Carefully Choose the Channel Scanning Order ­ Avoid Switching from a Large to a Small Input Range–Switching from a channel
with a large input range to a channel with a small input range can greatly increase the settling time. Suppose a 4 V signal is connected to channel 0 and a 1 mV signal is connected to channel 1. The input range for channel 0 is -10 V to 10 V and the input range of channel 1 is -200 mV to 200 mV. When the multiplexer switches from channel 0 to channel 1, the input to the NI-PGIA switches from 4 V to 1 mV. The approximately 4 V step from 4 V to 1 mV is 1,000% of the new full-scale range. For a 16-bit device to settle within 0.0015% (15 ppm or 1 LSB) of the ±200 mV full-scale range on channel 1, the input circuitry must settle to within 0.000031% (0.31 ppm or 1/50 LSB) of the ±10 V range. Some devices can take many microseconds for the circuitry to settle this much. To avoid this effect, you should arrange your channel scanning order so that transitions from large to small input ranges are infrequent. In general, you do not need this extra settling time when the NI- PGIA is switching from a small input range to a larger input range. ­ Insert Grounded Channel between Signal Channels–Another technique to improve settling time is to connect an input channel to ground. Then insert this channel in the scan list between two of your signal channels. The input range of the grounded channel should match the input range of the signal after the grounded channel in the scan list.
© National Instruments | 4-7

Chapter 4 Analog Input
Consider again the example above where a 4 V signal is connected to channel 0 and a 1 mV signal is connected to channel 1. Suppose the input range for channel 0 is -10 V to 10 V and the input range of channel 1 is -200 mV to 200 mV. You can connect channel 2 to AI GND (or you can use the internal ground; refer to Internal Channels in the NI-DAQmx Help). Set the input range of channel 2 to -200 mV to 200 mV to match channel 1. Then scan channels in the order: 0, 2, 1. Inserting a grounded channel between signal channels improves settling time because the NI-PGIA adjusts to the new input range setting faster when the input is grounded. ­ Minimize Voltage Step between Adjacent Channels–When scanning between channels that have the same input range, the settling time increases with the voltage step between the channels. If you know the expected input range of your signals, you can group signals with similar expected ranges together in your scan list. For example, suppose all channels in a system use a -5 to 5 V input range. The signals on channels 0, 2, and 4 vary between 4.3 V and 5 V. The signals on channels 1, 3, and 5 vary between -4 V and 0 V. Scanning channels in the order 0, 2, 4, 1, 3, 5 produces more accurate results than scanning channels in the order 0, 1, 2, 3, 4, 5. 4. Avoid Scanning Faster Than Necessary–Designing your system to scan at slower speeds gives the NI-PGIA more time to settle to a more accurate level. Here are two examples to consider: ­ Example 1–Averaging many AI samples can increase the accuracy of the reading by decreasing noise effects. In general, the more points you average, the more accurate the final result. However, you may choose to decrease the number of points you average and slow down the scanning rate. Suppose you want to sample 10 channels over a period of 20 ms and average the results. You could acquire 500 points from each channel at a scan rate of 250 kS/s. Another method would be to acquire 1,000 points from each channel at a scan rate of 500 kS/s. Both methods take the same amount of time. Doubling the number of samples averaged (from 500 to 1,000) decreases the effect of noise by a factor of 1.4 (the square root of 2). However, doubling the number of samples (in this example) decreases the time the NI- PGIA has to settle from 4 s to 2 s. In some cases, the slower scan rate system returns more accurate results. ­ Example 2–If the time relationship between channels is not critical, you can sample from the same channel multiple times and scan less frequently. For example, suppose an application requires averaging 100 points from channel 0 and averaging 100 points from channel 1. You could alternate reading between channels–that is, read one point from channel 0, then one point from channel 1, and so on. You also could read all 100 points from channel 0 then read 100 points from channel 1. The second method switches between channels much less often and is affected much less by settling time.
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M Series User Manual
Analog Input Data Acquisition Methods
When performing analog input measurements, you either can perform software- timed or hardware-timed acquisitions.
Software-Timed Acquisitions
With a software-timed acquisition, software controls the rate of the acquisition. Software sends a separate command to the hardware to initiate each ADC conversion. In NI-DAQmx, software-timed acquisitions are referred to as having on-demand timing. Software-timed acquisitions are also referred to as immediate or static acquisitions and are typically used for reading a single sample of data.
Hardware-Timed Acquisitions
With hardware-timed acquisitions, a digital hardware signal (AI Sample Clock) controls the rate of the acquisition. This signal can be generated internally on your device or provided externally.
Hardware-timed acquisitions have several advantages over software-timed acquisitions: · The time between samples can be much shorter. · The timing between samples is deterministic. · Hardware-timed acquisitions can use hardware triggering.
Hardware-timed operations can be buffered or non-buffered. A buffer is a temporary storage in computer memory for to-be-generated samples. · Buffered–In a buffered acquisition, data is moved from the DAQ device’s onboard FIFO
memory to a PC buffer using DMA or interrupts before it is transferred to application memory. Buffered acquisitions typically allow for much faster transfer rates than non-buffered acquisitions because data is moved in large blocks, rather than one point at a time. One property of buffered I/O operations is the sample mode. The sample mode can be either finite or continuous. ­ Finite sample mode acquisition refers to the acquisition of a specific, predetermined
number of data samples. Once the specified number of samples has been read in, the acquisition stops. If you use a reference trigger, you must use finite sample mode. ­ Continuous acquisition refers to the acquisition of an unspecified number of samples. Instead of acquiring a set number of data samples and stopping, a continuous acquisition continues until you stop the operation. Continuous acquisition is also referred to as double-buffered or circular-buffered acquisition.
© National Instruments | 4-9

Chapter 4 Analog Input
If data cannot be transferred across the bus fast enough, the FIFO becomes full. New acquisitions overwrite data in the FIFO before it can be transferred to host memory. The device generates an error in this case. With continuous operations, if the user program does not read data out of the PC buffer fast enough to keep up with the data transfer, the buffer could reach an overflow condition, causing an error to be generated. · Non-buffered–In non-buffered acquisitions, data is read directly from the FIFO on the device. Typically, hardware-timed, non-buffered operations are used to read single samples with known time increments between them. Note (NI USB-62xx Devices) USB M Series devices do not support non-buffered hardware-timed operations.
Analog Input Triggering
Analog input supports three different triggering actions: · Start trigger · Reference trigger · Pause trigger Refer to the AI Start Trigger Signal, AI Reference Trigger Signal, and AI Pause Trigger Signal sections for information about these triggers. An analog or digital trigger can initiate these actions. All M Series devices support digital triggering, but some do not support analog triggering. To find your device triggering options, refer to the specifications document for your device.
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M Series User Manual

Connecting Analog Input Signals

Table 4-3 summarizes the recommended input configuration for both types of signal sources.

Table 4-3. Analog Input Configuration

AI Ground-Reference
Setting*
Differential (DIFF)

Floating Signal Sources (Not Connected to Building Ground)
Examples: · Ungrounded thermocouples · Signal conditioning with isolated
outputs · Battery devices

Signal Source
+ ­

DAQ Device AI+
+ AI­
­

Ground-Referenced Signal Sources
Example: · Plug-in instruments with
non-isolated outputs

Signal Source
+ ­

DAQ Device AI+
+ AI­
­

AI GND

AI GND

Non-Referenced Single-Ended (NRSE)

Signal Source
+ ­

DAQ Device AI

• ­ AI SENSE AI GND

Signal Source
+ ­

DAQ Device AI

• ­ AI SENSE AI GND

Referenced Single-Ended (RSE)

Signal Source
+ ­

DAQ Device AI
+ ­
AI GND

NOT RECOMMENDED

Signal Source

DAQ Device

AI +

­

­

VA

VB

AI GND

Ground-loop potential (VA ­ VB) are added to measured signal.

• Refer to the Analog Input Ground-Reference Settings section for descriptions of the RSE, NRSE, and DIFF modes and software considerations. Refer to the Connecting Ground-Referenced Signal Sources section for more information.

© National Instruments | 4-11

Chapter 4 Analog Input
Connecting Floating Signal Sources
What Are Floating Signal Sources?
A floating signal source is not connected to the building ground system, but has an isolated ground-reference point. Some examples of floating signal sources are outputs of transformers, thermocouples, battery-powered devices, optical isolators, and isolation amplifiers. An instrument or device that has an isolated output is a floating signal source.
When to Use Differential Connections with Floating Signal Sources
Use DIFF input connections for any channel that meets any of the following conditions: · The input signal is low level (less than 1 V). · The leads connecting the signal to the device are greater than 3 m (10 ft). · The input signal requires a separate ground-reference point or return signal. · The signal leads travel through noisy environments. · Two analog input channels, AI+ and AI-, are available for the signal.
DIFF signal connections reduce noise pickup and increase common-mode noise rejection. DIFF signal connections also allow input signals to float within the common-mode limits of the NI-PGIA.
Refer to the Using Differential Connections for Floating Signal Sources section for more information about differential connections.
When to Use Non-Referenced Single-Ended (NRSE) Connections with Floating Signal Sources
Only use NRSE input connections if the input signal meets the following conditions: · The input signal is high-level (greater than 1 V). · The leads connecting the signal to the device are less than 3 m (10 ft).
DIFF input connections are recommended for greater signal integrity for any input signal that does not meet the preceding conditions.
In the single-ended modes, more electrostatic and magnetic noise couples into the signal connections than in DIFF configurations. The coupling is the result of differences in the signal path. Magnetic coupling is proportional to the area between the two signal conductors. Electrical coupling is a function of how much the electric field differs between the two conductors.
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M Series User Manual
With this type of connection, the NI-PGIA rejects both the common-mode noise in the signal and the ground potential difference between the signal source and the device ground.
Refer to the Using Non-Referenced Single-Ended (NRSE) Connections for Floating Signal Sources section for more information about NRSE connections.
When to Use Referenced Single-Ended (RSE) Connections with Floating Signal Sources
Only use RSE input connections if the input signal meets the following conditions: · The input signal can share a common reference point, AI GND, with other signals that
use RSE. · The input signal is high-level (greater than 1 V). · The leads connecting the signal to the device are less than 3 m (10 ft).
DIFF input connections are recommended for greater signal integrity for any input signal that does not meet the preceding conditions.
In the single-ended modes, more electrostatic and magnetic noise couples into the signal connections than in DIFF configurations. The coupling is the result of differences in the signal path. Magnetic coupling is proportional to the area between the two signal conductors. Electrical coupling is a function of how much the electric field differs between the two conductors.
With this type of connection, the NI-PGIA rejects both the common-mode noise in the signal and the ground potential difference between the signal source and the device ground.
Refer to the Using Referenced Single-Ended (RSE) Connections for Floating Signal Sources section for more information about RSE connections.
Using Differential Connections for Floating Signal Sources
It is important to connect the negative lead of a floating source to AI GND (either directly or through a bias resistor). Otherwise, the source may float out of the maximum working voltage range of the NI-PGIA and the DAQ device returns erroneous data.
The easiest way to reference the source to AI GND is to connect the positive side of the signal to AI+ and connect the negative side of the signal to AI GND as well as to AI- without using resistors. This connection works well for DC-coupled sources with low source impedance (less than 100 ).
Note (NI USB-62xx BNC Devices) To measure a floating signal source on USB BNC devices, move the switch under the BNC connector to the FS position.
© National Instruments | 4-13

Chapter 4 Analog Input

Figure 4-4. Differential Connections for Floating Signal Sources without Bias Resistors

Floating +

Signal Source

V­s

Impedance <100

M Series Device AI+
AI­ AI SENSE AI GND

However, for larger source impedances, this connection leaves the DIFF signal path significantly off balance. Noise that couples electrostatically onto the positive line does not couple onto the negative line because it is connected to ground. This noise appears as a DIFF-mode signal instead of a common-mode signal, and thus appears in your data. In this case, instead of directly connecting the negative line to AI GND, connect the negative line to AI GND through a resistor that is about 100 times the equivalent source impedance. The resistor puts the signal path nearly in balance, so that about the same amount of noise couples onto both connections, yielding better rejection of electrostatically coupled noise. This configuration does not load down the source (other than the very high input impedance of the NI-PGIA).
Figure 4-5. Differential Connections for Floating Signal Sources with Single Bias Resistor

Floating Signal Source

+ Vs ­

R is about

R

100 times

source

impedance

of sensor

M Series Device AI+
AI­ AI SENSE AI GND

You can fully balance the signal path by connecting another resistor of the same value between the positive input and AI GND, as shown in Figure 4-6. This fully balanced configuration offers slightly better noise rejection, but has the disadvantage of loading the source down with the series combination (sum) of the two resistors. If, for example, the source impedance is 2 k and each of the two resistors is 100 k, the resistors load down the source with 200 k and produce a -1% gain error.

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M Series User Manual
Figure 4-6. Differential Connections for Floating Signal Sources with Balanced Bias Resistors

AI+

Bias

Resistors

Floating

(see text) +

Signal Vs

Source ­

AI­

Bias Current Return Paths

Input Multiplexers AI SENSE

Instrumentation

Amplifier

PGIA ­

+ Measured
Vm Voltage ­

AI GND

I/O Connector

M Series Module/Device Configured in Differential Mode

Both inputs of the NI-PGIA require a DC path to ground in order for the NI- PGIA to work. If the source is AC coupled (capacitively coupled), the NI-PGIA needs a resistor between the positive input and AI GND. If the source has low- impedance, choose a resistor that is large enough not to significantly load the source but small enough not to produce significant input offset voltage as a result of input bias current (typically 100 k to 1 M). In this case, connect the negative input directly to AI GND. If the source has high output impedance, balance the signal path as previously described using the same value resistor on both the positive and negative inputs; be aware that there is some gain error from loading down the source, as shown in Figure 4-7.

© National Instruments | 4-15

Chapter 4 Analog Input

Figure 4-7. Differential Connections for AC Coupled Floating Sources with Balanced Bias Resistors

AC Coupled Floating Signal Source

AC Coupling
+ Vs ­

M Series Device AI+
AI­ AI SENSE AI GND

Using Non-Referenced Single-Ended (NRSE) Connections for Floating Signal Sources
It is important to connect the negative lead of a floating signals source to AI GND (either directly or through a resistor). Otherwise the source may float out of the valid input range of the NI-PGIA and the DAQ device returns erroneous data.

Note (NI USB-62xx BNC Devices) To measure a floating signal source on USB BNC devices, move the switch under the BNC connector to the FS position.

Figure 4-8 shows a floating source connected to the DAQ device in NRSE mode. Figure 4-8. NRSE Connections for Floating Signal Sources

Floating Signal Source

+ Vs ­

R

M Series Device AI
AI SENSE AI GND

All of the bias resistor configurations discussed in the Using Differential Connections for Floating Signal Sources section apply to the NRSE bias resistors as well. Replace AI- with AI SENSE in Figures 4-4, 4-5, 4-6, and 4-7 for configurations with zero to two bias resistors. The noise rejection of NRSE mode is better than RSE mode because the AI SENSE connection is made remotely near the source. However, the noise rejection of NRSE mode is worse than DIFF mode because the AI SENSE connection is shared with all channels rather than being cabled in a twisted pair with the AI+ signal.
Using the DAQ Assistant, you can configure the channels for RSE or NRSE input modes. Refer to the Configuring AI Ground-Reference Settings in Software section for more information about the DAQ Assistant.

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M Series User Manual
Using Referenced Single-Ended (RSE) Connections for Floating Signal Sources
Figure 4-9 shows how to connect a floating signal source to the M Series device configured for RSE mode.
Figure 4-9. RSE Connections for Floating Signal Sources

AI <0..n>

Floating

Signal Vs

Source

­

I/O Connector

Input Multiplexers AI SENSE
AI GND

Programmable Gain

Instrumentation Amplifier

PGIA

­

Vm

Measured Voltage

­

Selected Channel in RSE Configuration

Note (NI USB-62xx BNC Devices) To measure a floating signal source on USB BNC devices, move the switch under the BNC connector to the FS position.

Using the DAQ Assistant, you can configure the channels for RSE or NRSE input modes. Refer to the Configuring AI Ground-Reference Settings in Software section for more information about the DAQ Assistant.
Connecting Ground-Referenced Signal Sources

What Are Ground-Referenced Signal Sources?
A ground-referenced signal source is a signal source connected to the building system ground. It is already connected to a common ground point with respect to the device, assuming that the computer is plugged into the same power system as the source. Non-isolated outputs of instruments and devices that plug into the building power system fall into this category.
The difference in ground potential between two instruments connected to the same building power system is typically between 1 and 100 mV, but the difference can be much higher if power distribution circuits are improperly connected. If a grounded signal source is incorrectly measured, this difference can appear as measurement error. Follow the connection instructions for grounded signal sources to eliminate this ground potential difference from the measured signal.

© National Instruments | 4-17

Chapter 4 Analog Input
When to Use Differential Connections with Ground-Referenced Signal Sources
Use DIFF input connections for any channel that meets any of the following conditions: · The inp

References

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