NATIONAL INSTRUMENTS PCI-6731 Analog Output Board Instruction Manual

NATIONAL INSTRUMENTS PCI-6731 Analog Output Board

Product Information: PCI-6731

The PCI-6731 is a PCI/PXI/CompactPCI Analog Output (AO) device manufactured by National Instruments (NI). It is part of the NI 671X/673X series, which includes the NI 6711, NI 6713, NI 6715, NI 6731, and NI 6733 models. This device allows for high-precision voltage output and is commonly used in PC- based measurement systems.

Calibration Procedure
The provided user manual contains instructions for calibrating the NI 671X/673X devices using the Traditional NI-DAQ software. Calibration is essential to ensure the accuracy of measurements performed with the device. The frequency of calibration depends on the measurement requirements of your application, with NI recommending a complete calibration at least once a year. However, you may choose to perform calibration more frequently, such as every 90 days or every six months, based on your application’s demands.

Calibration Options: Internal Versus External

The NI 671X/673X devices offer two calibration options: internal (self- calibration) and external calibration.

• Internal Calibration: The internal calibration is a self-calibration process performed by the device itself. This process adjusts the calibration constants stored in the device to maintain accuracy.

  ---

• External Calibration: External calibration requires additional equipment, including a calibrator and a high-precision Digital Multimeter (DMM). During external calibration, the DMM supplies and reads voltages from the device. Adjustments are made to the device calibration constants to ensure that reported voltages meet device specifications. The new calibration constants are then stored in the device’s EEPROM. External calibration provides a set of calibration constants that can be used to compensate for measurement errors.

Equipment and Other Test Requirements

To perform the calibration of an NI 671X/673X device, the following equipment and test conditions are required:

• Test Equipment: A calibrator and a high-precision Digital Multimeter (DMM) are necessary. NI recommends using an Agilent 3458A DMM or a substitute calibration standard that meets the required accuracy specifications. The DMM should be at least 40 ppm (0.004%) accurate for 12-bit devices and 10 ppm (0.001%) accurate for 16-bit devices. Custom connection hardware, such as the NI CB-68 connector block and appropriate cables, may also be needed for easy access to the device’s I/O connector.
• Test Conditions: The user manual provides guidelines for optimizing connections and test conditions during calibration. These guidelines ensure accurate and reliable calibration results.

Software
To perform the calibration, the calibration system must have the proper device driver installed. For the NI 671X/673X devices, the Traditional NI-DAQ software is required. It is recommended to install NI-DAQ from the official NI website (ni.com/downloads). NI-DAQ supports various programming languages, including LabVIEW, LabWindowsTM/CVITM, Microsoft Visual C++, Microsoft Visual Basic, and Borland C++. During installation, only install support for the programming language you intend to use for your application. By following the provided instructions and utilizing the recommended equipment and software, you can successfully calibrate your NI 671X/673X device to maintain accurate measurements in your application.

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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/CompactPCI 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, LabWindows™/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.

1. Launch Measurement & Automation Explorer (MAX).
2. Configure the NI 671X/673X device number.
3. 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:

1. 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.
2. 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.
3. 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_VWrite 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 time base 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 Device 671 X /673 X 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

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

Figure 1. Verifying Analog Output

Verifying the Counter

Figure 2. Verifying the Counter

Adjusting the NI 671X/673X

Figure 3. 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
• PCI-6731 National Instruments Analog Output Device | Apex Waves

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