NATIONAL INSTRUMENTS PXI-6733 Analog Output Module User Manual
- June 12, 2024
- NATIONAL INSTRUMENTS
Table of Contents
NATIONAL INSTRUMENTS
User Manual
PXI-6733 Analog Output Module
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NI 671X/673X Calibration Procedure
This document contains instructions for calibrating NI 671X (NI
6711/6713/6715) and the NI 673X (NI 6731/6733) PCI/PXI/Compact PCI Analog
Output (AO) devices with Traditional NI-DAQ. Use this calibration procedure
with the ni671xCal.dll file, which contains specific functions required for
calibrating NI 671X/673X devices.
The measurement requirements of your application determine how
often the NI 671X/673X must be calibrated to maintain accuracy. NI recommends
that you perform a complete calibration at least once every year. You can
shorten this interval to 90 days or six months based on the demands of your
application.
Note Refer to
ni.com/support/calibrat/mancal.htm
for a copy of the ni671xCal.dll file.
Calibration Options: Internal Versus External
The NI 671X/673X has two calibration options: an internal, or self-
calibration, and an external calibration.
Internal Calibration
Internal calibration is a much simpler calibration method that does not rely
on external standards. In this method, the device calibration constants are
adjusted with respect to a high-precision voltage source on the NI 671X/673X.
This type of calibration is used after the device has been calibrated with
respect to an external standard. However, external variables such as
temperature can still affect measurements. The new calibration constants are
defined with respect to the calibration constants created during an external
calibration, ensuring that the measurements can be traced back to the external
standards. In essence, internal calibration is similar to the auto-zero
function found on a digital multimeter (DMM).
External Calibration
External calibration requires using a calibrator and a high-precision DMM.
During external calibration, the DMM supplies and reads voltages from the
device. Adjustments are made to the device calibration constants to ensure
that the reported voltages are within the device specifications. The new
calibration constants are then stored in the device EEPROM. After the onboard
calibration constants have been adjusted, the high-precision voltage source on
the device is adjusted. An external calibration provides a set of calibration
constants that you can use to compensate for the error in the measurements
taken by the NI 671X/673X.
Equipment and Other Test Requirements
This section describes the equipment, test conditions, documentation, and
software you need to calibrate the NI 671X/673X.
Test Equipment
To calibrate an NI 671X/673X device, you need a calibrator and a digital
multimeter (DMM). NI recommends using the following test equipment:
- Calibrator—Fluke 5700A
- DMM—Agilent (HP) 3458A
If you do not have an Agilent 3458A DMM, use the accuracy specifications to
select a substitute calibration standard. To calibrate an NI 671X/673X device,
you need a high-precision DMM that is at least 40 ppm (0.004%) accurate. The
calibrator must be at least 50 ppm (0.005%) accurate for 12-bit devices and 10
ppm (0.001%) accurate for 16-bit devices.
If you do not have custom connection hardware, you may need a connector block
such as the NI CB-68 and a cable such as the SH68-68-EP. For the NI 6715, use
the SHC68-68-EP cable. These components give you easy access to the individual
pins on the 68-pin I/O connector.
Test Conditions
Follow these guidelines to optimize connections and test conditions during
calibration:
- Keep connections to the NI 671X/673X short. Long cables and wires act as antennae, picking up extra noise, which can affect measurements.
- Use shielded copper wire for all cable connections to the device.
- Use twisted-pair wire to eliminate noise and thermal offsets.
- Maintain a temperature between 18 and 28 °C. To operate the module at a specific temperature outside this range, calibrate the device at that temperature.
- Keep relative humidity below 80%.
- Allow a warm-up time of at least 15 minutes to ensure that the measurement circuitry is at a stable operating temperature.
Software
Because the NI 671X/673X is a PC-based measurement device, you must have the
proper device driver installed in the calibration system before attempting
calibration. For this calibration procedure, you need Traditional NI-DAQ
installed on the calibration computer. NI-DAQ, which configures and controls
the NI 671X/673X, is available at ni.com/downloads.
NI-DAQ supports a number of programming languages, including LabVIEW, Lab
Windows ™ ™ /CVI , Microsoft Visual C++, Microsoft Visual Basic, and Borland
C++. When you install the driver, you only need to install support for the
programming language that you intend to use.
You also need copies of the ni671xCal.dll, ni671xCal.lib, and ni671xCal.h
files.
The DLL provides calibration functionality that does not reside in NI-DAQ,
including the ability to protect the calibration constants, update the
calibration date, and write to the factory calibration area. You can access
the functions in this DLL through any 32-bit compiler. The factory calibration
area and the calibration date should only be modified by a metrology
laboratory or another facility that maintains traceable standards.
Configuring the NI 671X/673X
The NI 671X/673X must be configured in NI-DAQ, which automatically detects the
device. The following steps briefly explain how to configure the device in NI-
DAQ. Refer to the NI 671X/673X User Manual for detailed installation
instructions. You can install this manual when you install NI-DAQ.
- Launch Measurement & Automation Explorer (MAX).
- Configure the NI 671X/673X device number.
- Click Test Resources to ensure that the NI 671X/673X is properly working.
The NI 671X/673X is now configured.
Note After a device is configured in MAX, the device is assigned a device
number, which is used in each of the function calls to identify which DAQ
device to calibrate.
Writing the Calibration Procedure
The calibration procedure in the Calibrating the NI 671X/673X section provides
step-by-step instructions for calling the appropriate calibration functions.
These calibration functions are C function calls from NI-DAQ that are also
valid for Microsoft Visual Basic and Microsoft Visual C++ programs. Although
LabVIEW VIs are not discussed in this procedure, you can program in LabVIEW
using the VIs that have similar names to the NI-DAQ function calls in this
procedure. Refer to the Flowcharts section for illustrations of the code used
at each step of the calibration procedure.
Often you must follow a number of compiler-specific steps to create an
application that uses NI-DAQ. Refer to the NI-DAQ User Manual for PC
Compatibles document at ni.com/manuals for details about the required steps
for each of the supported compilers.
Many of the functions listed in the calibration procedure use variables that
are defined in the nidaqcns.h file. To use these variables, you must include
the nidaqcns.h file in the code. If you do not want to use these variable
definitions, you can examine the function call listings in the NI-DAQ
documentation and the nidaqcns.h file to determine what input values are
required.
Documentation
For information about NI-DAQ, refer to the following documentation:
- Traditional NI-DAQ Function Reference Help (Start» Programs» National Instruments» Traditional NI-DAQ Function Reference Help)
- NI-DAQ User Manual for PC Compatibles at ni.com/manuals
These two documents provide detailed information about using NI-DAQ.
The function reference help includes information about the functions in NI-
DAQ. The user manual provides instructions for installing and configuring DAQ
devices and detailed information about creating applications that use NI-DAQ.
These documents are the primary references for writing the calibration
utility. For further information about the device you are calibrating, you
also may want to install the device documentation.
Calibrating the NI 671X/673X
To calibrate the NI 671X/673X, complete the following steps:
- Verify the performance of the NI 671X/673X. This step, which is described in the Verifying the Performance of the NI 671X/673X section, confirms whether the device is in specification prior to adjustment.
- Adjust the NI 671X/673X calibration constants with respect to a known voltage source. This step is described in the Adjusting the NI 671X/673X section.
- Re-verify the performance to ensure that the NI 671X/673X is operating within its specifications after adjustment.
Note To find out the date of the last calibration, call Get_Cal_Date,
which is included in the ni671x.dll. CalDate stores the date when the device
was last calibrated.
Verifying the Performance of the NI 671X/673X
Verification determines how well the device is meeting its specifications.
The verification procedure is divided into the major functions of the device.
Throughout the verification process, refer to the tables in the Specifications
section to determine if the device needs adjustment.
Verifying Analog Output
This procedure verifies the AO performance of the NI 671X/673X.
NI recommends testing all channels of the device. However, to save time, you
can test only the channels used in your application. After reading the
Equipment and Other Test Requirements section, complete the following steps:
-
Disconnect all cables to the device. Make sure the device is not connected to any circuits other than those specified by the calibration procedure.
-
To internally calibrate the device, call the Calibrate_E_Series function with the following parameters set as indicated:
• calOP set to ND_SELF_CALIBRATE
• setOfCalConst set to ND_USER_EEPROM_AREA
• calRefVolts set to 0 -
Connect the DMM to DAC0OUT as shown in Table 1.
Table 1. Connecting the DMM to DAC0OUT Output Channel| DMM Positive Input| DMM Negative Input
---|---|---
DAC0OUT| DAC0OUT (pin 22)| AOGND (pin 56)
DAC1OUT| DAC1OUT (pin 21)| AOGND (pin 55)
DAC2OUT| DAC2OUT (pin 57)| AOGND (pin 23)
DAC3OUT| DAC3OUT (pin 25)| AOGND (pin 58)
DAC4OUT| DAC4OUT (pin 60)| AOGND (pin 26)
DAC5OUT| DAC5OUT (pin 28)| AOGND (pin 61)
DAC6OUT| DAC6OUT (pin 30)| AOGND (pin 63)
DAC7OUT| DAC7OUT (pin 65)| AOGND (pin 63)
Note: Pin numbers are given for 68-pin I/O connectors only. If you are using a 50-pin I/O connector, refer to the device documentation for signal connection locations. -
Refer to the table from the Specifications section that corresponds to the device you are verifying. This specification table shows all acceptable settings for the device.
-
Call AO_ Configure to configure the device for the appropriate device number, channel, and output polarity (the NI 671X/673X devices support only bipolar output range). Use channel 0 as the channel to verify. Read the remaining settings from the specification table for the device.
-
Call AO_ V Write to update the AO channel with the appropriate voltage. The voltage value is in the specification table.
-
Compare the resulting value shown by the DMM to the upper and lower limits on the specification table. If the value is between these limits, the device has passed the test.
-
Repeat steps 3 through 5 until you have tested all values.
-
Disconnect the DMM from DAC0OUT, and reconnect it to the next channel, making the connections from Table 1.
-
Repeat steps 3 through 9 until you have verified all channels.
-
Disconnect the DMM from the device.
You have now verified the AO channels of the device.
Verifying the Performance of the Counter
This procedure verifies the performance of the counter. The NI 671X/673X
devices have only one timebase to verify, so you only need to verify counter
0. Because you cannot adjust this timebase, you can only verify the
performance of counter 0. After reading the Equipment and Other Test
Requirements section, complete the following steps:
-
Connect the counter positive input to GPCTR0_OUT (pin 2) and the counter negative input to DGND (pin 35).
Note Pin numbers are given for 68-pin I/O connectors only. If you are using a 50-pin I/O connector, refer to the device documentation for signal connection locations. -
Call GPCTR_ Control with action set to ND_RESET to place the counter in a default state.
-
Call GPCTR Set Application with application set to ND_PULSE_TRAIN_GNR to configure the counter for pulse-train generation.
-
Call GPCTR_Change_Parameter with paramID set to ND_COUNT_1 and paramValue set to 2 to configure the counter to output a pulse with an off time of 100 ns.
-
Call GPCTR_Change_Parameter with paramID set to ND_COUNT_2 and paramValue set to 2 to configure the counter to output a pulse with an on time of 100 ns.
-
Call Select_Signal with signal and source set to ND_GPCTR0_OUTPUT and source spec set to ND_LOW_TO_HIGH to route the counter signal to the GPCTR0_OUT pin on the device I/O connector.
-
Call GPCTR_Control with action set to ND_PROGRAM to start the generation of the square wave. The device begins to generate a 5 MHz square wave when GPCTR_Control completes execution.
-
Compare the value read by the counter to the test limits shown in the appropriate table in the Specifications section. If the value is between these limits, the device has passed this test.
-
Disconnect the counter from the device.
You have now verified the device counter.
Adjusting the NI 671X/673X
This procedure adjusts the AO calibration constants. At the end of each
calibration procedure, these new constants are stored in the factory area of
the device EEPROM. An end-user cannot modify these values, which provides a
level of security that ensures users do not accidentally access or modify any
calibration constants adjusted by the metrology laboratory.
This step in the calibration process calls functions in NI-DAQ and in the
ni671x.dll. For further information about the functions in the ni671x.dll,
refer to the comments in the ni671x.h file.
-
Disconnect all cables to the device. Make sure the device is not connected to any circuits other than those specified by the calibration procedure.
-
To internally calibrate the device, call the Calibrate_ E_Series function with the following parameters set as indicated:
• calOP set to ND_SELF_CALIBRATE
• setOfCalConst set to ND_USER_EEPROM_AREA
• calRefVolts set to 0 -
Connect the calibrator to the device according to Table 2.
Table 2. Connecting the Calibrator to the Device671X/673X Pins| Calibrator
---|---
EXTREF (pin 20)| Output High
AOGND (pin 54)| Output Low
Note: Pin numbers are given for 68-pin connectors only. If you are using a 50-pin connector, refer to the device documentation for signal connection locations. -
Set the calibrator to output a voltage of 5.0 V.
-
Call Calibrate_E_Series with the following parameters set as indicated:
• calOP set to ND_EXTERNAL_CALIBRATE
• setOfCalConst set to ND_USER_EEPROM_AREA
• calRefVolts set to 5.0
Note If the voltage supplied by the source does not maintain a steady 5.0 V, you receive an error. -
Call Copy_Const to copy the new calibration constants to the factory-protected portion of the EEPROM. This function also updates the calibration date.
-
Disconnect the calibrator from the device.
The device is now adjusted with respect to the external source. After the device is adjusted, you can verify the AO operation by repeating the Verifying Analog Output section.
Specifications
The following tables are accuracy specifications to use when verifying and adjusting the NI 671X/673X. The tables show the specifications for 1-year and 24-hour calibration intervals.
Using the Tables
The following definitions describe how to use the specification tables in this
section.
Range
Range refers to the maximum allowable voltage range of an input or output
signal. For example, if a device is configured in bipolar mode with a range of
20 V, the device can sense signals between +10 and –10 V.
Polarity
Polarity refers to the positive and negative voltages of the input signal that
can be read. Bipolar means the device can read both positive and negative
voltages. Unipolar means that the device can read only positive voltages.
Test Point
The Test Point is the voltage value that is input or output for verification
purposes. This value is broken down into Location and Value. Location refers
to where the test value fits within the test range. Pos FS refers to positive
full-scale, and Neg FS refers to negative full-scale. Value refers to the
voltage to be verified, and Zero refers to the outputting of zero volts.
24-Hour Ranges
The 24-Hour Ranges column contains the upper limits and lower limits for the
test point value. If the device has been calibrated in the last 24 hours, the
test point value should be between the upper and lower limit values. These
limit values are expressed in volts.
1-Year Ranges
The 1-Year Ranges column contains the upper limits and lower limits for the
test point value. If the device has been calibrated in the last year, the test
point value should be between the upper and lower limit values. These limits
are expressed in volts.
Counters
Because you cannot adjust the resolution of the counter/timers, these values
do not have a 1-year or 24-hour calibration period. However, the test point
and upper and lower limits are provided for verification purposes.
Table 3. NI 671X Analog Output Values
Range (V)| Polarity| Test Point| 24-Hour Ranges|
1-Year Ranges
---|---|---|---|---
Location| Value (V)| Lower Limit (V)| Upper Limit (V)|
Lower Limit (V)| Upper Limit (V)
0| Bipolar| Zero| 0.0| –0.0059300| 0.0059300| –0.0059300| 0.0059300
20| Bipolar| Pos FS| 9.9900000| 9.9822988| 9.9977012| 9.9818792| 9.9981208
20| Bipolar| Neg FS| –9.9900000| –9.9977012| –9.9822988| –9.9981208|
–9.9818792
Table 4. NI 673X Analog Output Values
Range (V)| Polarity| Test Point| 24-Hour Ranges|
1-Year Ranges
---|---|---|---|---
Location| Value (V)| Lower Limit (V)| Upper Limit (V)|
Lower Limit (V)| Upper Limit (V)
0| Bipolar| Zero| 0.0| –0.0010270| 0.0010270| –0.0010270| 0.0010270
20| Bipolar| Pos FS| 9.9900000| 9.9885335| 9.9914665| 9.9883636| 9.9916364
20| Bipolar| Neg FS| –9.9900000| –9.9914665| –9.9885335| –9.9916364|
–9.9883636
Table 5. NI 671X/673X Counter Values
| Set Point (MHz) | Lower Limit (MHz) | Upper Limit (MHz) |
|---|---|---|
| 5 | 4.9995 | 5.0005 |
Flowcharts
These flowcharts show the appropriate NI-DAQ function calls for verifying and adjusting the NI 671X/673X. Refer to the Calibrating the NI 671X/673X section, the Traditional NI-DAQ Function Reference Help (Start» Programs» National Instruments» Traditional NI-DAQ Function Reference Help), and the NI-DAQ User Manual for PC Compatibles at ni.com/manuals for additional information about the software structure.
Verifying Analog Output
Verifying the Counter
Adjusting the NI 671X/673X
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References
- Test and Measurement Systems, a part of Emerson - NI
- Software and Driver Downloads - NI
- Product Documentation - NI
- Search Results - NI
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