National Instruments NI 9227 Manual

CALIBRATION PROCEDURE
NI 9227
This document contains the verification and adjustment procedures for the National
Instruments 9227. For more information about calibration solutions, visit ni.com/
calibration.
Contents
Software.................................................................................................................................... 1
Documentation.......................................................................................................................... 2
Test Equipment......................................................................................................................... 3
Test Conditions......................................................................................................................... 3
Initial Setup............................................................................................................................... 4
Verification ............................................................................................................................... 4
Accuracy Verification....................................................................................................... 5
Gain Matching Verification.............................................................................................. 6
Phase Matching Verification ............................................................................................ 8
Adjustment................................................................................................................................ 9
Accuracy Adjustment ....................................................................................................... 9
EEPROM Update ..................................................................................................................... 10
Reverification ........................................................................................................................... 10
Accuracy Under Calibration Conditions .................................................................................. 10
Worldwide Support and Services ............................................................................................. 11
Software
Calibrating the NI 9227 requires the installation of NI-DAQmx 9.3 or later on the calibration
system. You can download NI-DAQmx from ni.com/downloads. NI-DAQmx supports
LabVIEW, LabWindows™/CVI™, C/C++, C#, and Visual Basic .NET. When you install
NI-DAQmx, you only need to install support for the application software that you intend to use.

2|ni.com |NI 9227 Calibration Procedure
Documentation
Consult the following documents for information about the NI 9227, NI-DAQmx, and your
application software. All documents are available on ni.com and help files install with the
software.
NI cDAQ-9174/9178 USB Chassis Quick Start
NI-DAQmx installation and hardware setup
NI 9227 Operating Instructions and Specifications
NI 9227 specific information, specifications, and calibration interval
NI-DAQmx Readme
Operating system and application software support in NI-DAQmx
LabVIEW Help
LabVIEW programming concepts and reference information about NI-DAQmx
VIs and functions
NI-DAQmx C Reference Help
Reference information for NI-DAQmx C functions and NI-DAQmx C properties
NI-DAQmx .NET Help Support for Visual Studio
Reference information for NI-DAQmx .NET methods and NI-DAQmx .NET
properties, key concepts, and a C enum to .NET enum mapping table

NI 9227 Calibration Procedure |© National Instruments |3
Test Equipment
Table 1 lists the equipment recommended for the performance verification and adjustment
procedures. If the recommended equipment is not available, select a substitute using the
requirements listed in Table 1.
Test Conditions
The following setup and environmental conditions are required to ensure the NI 9227 meets
published specifications.
• Keep connections to the device as short as possible. Long cables and wires act as antennas,
picking up extra noise that can affect measurements.
• Verify that all connections to the device are secure.
• Use shielded copper wire for all cable connections to the device. Use twisted-pairs wire to
eliminate noise and thermal offsets.
• Maintain an ambient temperature of 23 °C ± 5 °C. The device temperature will be greater
than the ambient temperature.
• Keep relative humidity below 80%.
• Allow a warm-up time of at least 10 minutes to ensure that the NI 9227 measurement
circuitry is at a stable operating temperature.
Table 1. Recommended Equipment
Equipment
Recommended
Model Where Used Requirements
Calibrator Fluke 5522A Accuracy,
Adjustment
Use a high-precision current
source with an accuracy
±500 ppm of output + 500 μA.
Function
Generator
NI 5421 Gain Matching,
Phase Matching
Use a function generator with an
output impedance of 50 Ω
capable of sourcing both 1 kHz
and 20 kHz ±10 VPK AC
sinusoidal signals with
amplitude uncertainty of ±10%
to a 50 Ωload.
Termination
Resistor
—Gain Matching,
Phase Matching
50 Ω, 1 W, ±5%
Chassis NI cDAQ-9178 All —

4|ni.com |NI 9227 Calibration Procedure
Initial Setup
Complete the following steps to set up the NI 9227.
1. Install NI-DAQmx.
2. Make sure the NI cDAQ-9178 power source is not connected.
3. Connect the NI cDAQ-9178 to the system safety ground.
a. Attach a ring lug to a 14 AWG (1.6 mm) wire.
b. Connect the ring lug to the ground terminal on the side of the NI cDAQ-9178 using
the ground screw.
c. Attach the other end of the wire to the system safety ground.
4. Install the module in slot 8 of the NI cDAQ-9178 chassis. Leave slots 1 through 7 of the
NI cDAQ-9178 chassis empty.
5. Connect the NI cDAQ-9178 chassis to your host computer.
6. Connect the power source to the NI cDAQ-9178 chassis.
7. Launch Measurement & Automation Explorer (MAX).
8. Right-click the device name and select Self-Test to ensure that the module is working
properly.
Verification
The following performance verification procedures describes the sequence of operation and test
points required to verify the NI 9227 and assumes that adequate traceable uncertainties are
available for the calibration references.

NI 9227 Calibration Procedure |© National Instruments |5
Accuracy Verification
Complete the following procedure to determine the As-Found status of the NI 9227.
Note Completing the Accuracy verification procedure verifies both the 5 Arms and
10 Arms accuracy specifications listed the NI 9227 Operating Instructions and
Specifications.
1. Set the calibrator to Standby mode (STBY).
2. Connect the NI 9227 to the calibrator as shown in Figure 1.
Figure 1. Accuracy Verification Connections
3. Set the calibrator current to a Test Point value indicated in Table 4.
4. Set the calibrator to Operate mode (OPR).
5. Acquire and average samples.
a. Create and configure an AI current task according to Table 2.
b. Configure the task timing according to Table 3.
c. Start the task.
Table 2. NI 9227 Configuration for Accuracy Verification
Physical Channels
Minimum
(Arms)
Maximum
(Arms)
Terminal
Configuration
AI0:3 -5.0 5.0 Differential
Table 3. NI 9227 Timing Configuration for Accuracy Verification
Sample Mode Samples Per Channel Rate (kS/s)
Finite Samples 5000 50
NI 9227
Calibrator
HI
LO
AI1
–
+
AI0
–
+
AI2
–
+
AI3
–
+

6|ni.com |NI 9227 Calibration Procedure
d. Read samples from the NI 9227.
e. Average the samples.
f. Stop and clear the task.
6. Compare the per-channel averages to the limits in Table 4.
7. Set the calibrator to Standby mode (STBY).
8. Repeat steps 3 through 7 for each test point in Table 4.
9. Disconnect the calibrator from the device.
Note The test limits listed in Table 4 are derived using the values in Table 13.
Gain Matching Verification
Complete the following procedure to determine the As-Found status of the NI 9227.
1. Connect the NI 9227 to the function generator as shown in Figure 2.
Figure 2. Gain Matching Verification Connections
Table 4. NI 9227 Verification Test Limits for Accuracy
Range Test Point 1-Year Limits
Min
(Arms)
Max
(Arms)Location
Value
(ADC)
Lower Limit
(ADC)
Upper Limit
(ADC)
-5 5Max 5.00 4.990758 5.009242
Mid 0.00 -0.004242 0.004242
Min -5.00 -5.009242 -4.990758
NI 9227
Function Generator
HI 50 Ω
LO
AI1
–
+
AI0
–
+
AI2
–
+
AI3
–
+
50 Ω
~

NI 9227 Calibration Procedure |© National Instruments |7
2. Configure function generator according to Table 5.
3. Enable the function generator.
4. Acquire samples.
a. Create and configure an AI current task according to Table 6.
b. Configure the task timing according to Table 7.
c. Start the task.
d. Read samples from the NI 9227. Record the amplitude of the waveform as
AmplitudeAcq for each channel.
e. Clear the task.
5. Perform the following calculation for each channel using the AmplitudeAcq value to
calculate the gain for each channel.
6. Compare the channel-to-channel gain difference to the maximum limit of ±0.13 dB.
7. Disable the function generator.
8. Disconnect the calibrator from the device.
If the Gain Matching verification procedure determines that the NI 9227 is outside of the limits,
refer to Worldwide Support and Services for assistance in returning the device to NI.
Table 5. Function Generator Configuration for Gain Matching Verification
Signal Type Amplitude (VPK) Frequency (kHz)
Sinewave 9 20
Table 6. NI 9227 Configuration for Gain Matching Verification
Physical Channels Terminal Configuration
AI0:3 Differential
Table 7. NI 9227 Configuration for Gain Matching Verification
Sample Mode Samples Per Channel Rate (kS/s)
Finite Samples 25000 50
Amplitude dB() 20 log10 ×AmplitudeAcq
90mA
----------------------------------- 





=

8|ni.com |NI 9227 Calibration Procedure
Phase Matching Verification
Complete the following procedure to determine the As-Found status of the NI 9227.
1. Connect the NI 9227 to the function generator as shown in Figure 3.
Figure 3. Phase Matching Verification Connections
2. Configure function generator according to Table 8.
3. Set the function generator frequency to a value indicated in Table 11.
4. Enable the function generator.
5. Acquire samples.
a. Create and configure an AI current task according to Table 9.
b. Configure the task timing according to Table 10.
c. Start the task.
Table 8. Function Generator Configuration for Phase Matching Verification
Signal Type Amplitude (VPK) Frequency (kHz)
Sinewave 9 20
Table 9. NI 9227 Configuration for Phase Matching Verification
Physical Channels Channel Configuration
AI0:3 DC Coupled
Table 10. NI 9227 Configuration for Phase Matching Verification
Sample Mode Samples Per Channel Rate (kS/s)
Finite Samples 25000 50
NI 9227
Function Generator
HI 50 Ω
LO
AI1
–
+
AI0
–
+
AI2
–
+
AI3
–
+
50 Ω
~

NI 9227 Calibration Procedure |© National Instruments |9
d. Read samples from the NI 9227. Record this measurement for each channel.
e. Clear the task.
6. Calculate the phase for each channel on the NI 9227. NI recommends using the Extract
Single Tone Information VI to calculate phase.
7. Compare the channel-to-channel phase difference to the limits in Table 11.
8. Repeat steps 2 through 7 for each test point in Table 11.
9. Disable the function generator.
10. Disconnect the function generator from the device.
If the Phase Matching verification procedure determines that the NI 9227 is outside of the limits,
refer to Worldwide Support and Services for assistance in returning the device to NI.
Adjustment
The following performance adjustment procedure describes the sequence of operation required
to adjust the NI 9227.
Accuracy Adjustment
Complete the following procedure to adjust the accuracy performance of the NI 9227.
Note Completing the Accuracy adjustment procedure adjusts the NI 9227 to meet
both the 5 Arms and 10 Arms accuracy specifications listed in the NI 9227 Operating
Instructions and Specifications.
1. Set the calibrator to Standby mode (STBY).
2. Connect the NI 9227 to the calibrator as shown in Figure 1.
3. Adjust the NI 9227.
a. Initialize a calibration session on the NI 9227. The default password is NI.
b. Input the external temperature in degrees Celsius.
c. Call the NI 9227 get C Series adjustment points function to obtain an array of
recommended calibration currents for the NI 9227.
d. Set the calibrator to a reference value determined by the array of recommended
calibration currents.
Table 11. NI 9227 Verification Test Limits for Phase Matching
Generator Frequency (kHz) Phase Matching Channel-to-Channel Limit
1±0.100°
20 ±2.000°

10 |ni.com |NI 9227 Calibration Procedure
e. Set the calibrator to Operate mode (OPR).
f. Call and configure the NI 9227 adjustment function according to Table 12.
g. Set the calibrator to Standby mode (STBY).
h. Repeat steps d through g for each calibration current in the array.
i. Close the calibration session.
4. Disconnect the NI 9227 from the calibrator.
EEPROM Update
When an adjustment procedure is completed, the NI 9227 internal calibration memory
(EEPROM) is immediately updated.
If you do not want to perform an adjustment, you can update the calibration date and onboard
calibration temperature without making any adjustments by initializing an external calibration,
setting the C Series calibration temperature, and closing the external calibration.
Reverification
Repeat the Verification section to determine the As-Left status of the device.
Note If any test fails Reverification after performing an adjustment, verify that you
have met the Test Conditions before returning your device to NI. Refer to Worldwide
Support and Services for assistance in returning the device to NI.
Accuracy Under Calibration Conditions
The following calibration specifications are valid under the following conditions:
• Ambient temperature 23 °C ± 5 °C
• NI 9227 installed in slot 8 of an NI cDAQ-9178 chassis
• Slots 1 through 7 of the NI cDAQ-9178 chassis are empty
Table 12. Adjustment Configuration
Physical Channel Reference Value
cDAQMod8/aixThe actual value of the current output of the calibrator