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 National Instruments Corporation

13

NI 9235/9236 Calibration Procedure

5.

If you use C function calls, create a task using 

DAQmxCreateTa

s

k

, 

as shown in the following table. If you use LabVIEW, skip this step. 
The task is created in step 6 in LabVIEW.

6.

Create and configure an AI Custom Voltage with Excitation channel 
using the DAQmx Create Virtual Channel VI, as shown in the 
following table.

Note

Throughout the procedure, refer to the NI-DAQmx function parameters for the 

LabVIEW input values. Refer to the block diagram images for the correct instance to use 
for polymorphic VIs.

LabVIEW Block Diagram

NI-DAQmx Function Call

LabVIEW does not require this step.

Call 

DAQmxCreateTa

s

k

 with the following parameters:

taskName

: 

SCVerificationTask

taskHandle

: 

&ta

s

kHandle

LabVIEW Block Diagram

NI-DAQmx Function Call

Call 

DAQmxCreateAIVoltageChan

WithExcit

 with the following 

parameters:

taskHandle

: 

ta

s

kHandle

physicalChannel

: 

dev1/ai

x

*

nameToAssignToChannel

: 

myVoltageChannel

terminalConfig

: 

DAQmx_Val_Cfg_Default

minVal

: 

–0.027

maxVal

: 

0.027

units

: 

DAQmx_Val_Volt

s

bridgeConfig

: 

DAQmx_Val_QuarterBridge

voltageExcitSource

: 

DAQmx_Val_Internal

voltageExcitVal

:

2.0

 for the NI 9235

3.3

 for the NI 9236

useExcitforScaling

: 

TRUE

customScaleName

: 

NULL

* 

x

 refers to the channel number.

Содержание 9235

Страница 1: ...ions You can install these help files when you install NI DAQmx on the calibration computer Contents Conventions 2 Software 2 Documentation 3 Calibration Interval 3 Test Equipment 4 Test Conditions 4 Calibration Procedure 5 Calibration Process Overview 5 Initial Setup 5 Connecting the Calibrator to the Module 6 Verification Procedures 8 Measurement Accuracy Verification 8 Shunt Calibration Accurac...

Страница 2: ...his font is also used for the proper names of disk drives paths directories programs subprograms subroutines device names functions operations variables filenames and extensions monospace italic Italic text in this font denotes text that is a placeholder for a word or value that you must supply Software Install NI DAQmx 8 8 or later on the calibration computer NI DAQmx includes high level function...

Страница 3: ...that your device is operating properly To access this guide select Start All Programs National Instruments NI DAQ DAQ Getting Started Guide Note The documents above are installed with NI DAQmx You can also download the latest versions from the NI Web site at ni com manuals NI 9235 9236 Operating Instructions and Specifications This document describes how to use the NI 9235 9236 and includes specif...

Страница 4: ...t 10 minutes to ensure that the measurement circuitry is at a stable operating temperature Table 1 Recommended Equipment Equipment Recommended Model Requirements Calibrator Fluke 5500A If this instrument is unavailable use a calibrator with generation of resistances in the ranges of 108 Ω 132 Ω and 315 Ω 385 Ω with 0 01 Ω resolution an accuracy of at least 90 ppm and automatic lead wire compensati...

Страница 5: ...e operates within its specifications after adjustment The first two steps are explained in the following sections Initial Setup You must configure the device in Measurement Automation Explorer MAX to communicate with NI DAQmx Complete the following steps to configure a device in MAX 1 Install the NI DAQmx driver software 2 Make sure that no power is connected to the module terminals If the system ...

Страница 6: ... the module channel you want to verify Leave all other channels unconnected Note The three connections to the calibrator LO terminal must be connected at the calibrator output jack Note Ensure that the connection resistance between the calibrator LO terminal and the module RC terminal meets the requirement listed in Table 1 4 Connect the HI terminal of the calibrator to the EXC0 terminal of the mo...

Страница 7: ...ator to Module Connections Refer to Figure 2 for the terminal assignments of the NI 9235 9236 Figure 2 NI 9235 9236 Terminal Assignments Fluke 5500A AUX HI EXC1 EXC0 AI0 RC0 AUX LO HI LO NI 9235 9236 EXC0 AI0 RC0 EXC2 AI2 RC2 EXC4 AI4 RC4 EXC6 AI6 RC6 EXC1 AI1 RC1 EXC3 AI3 RC3 EXC5 AI5 RC5 EXC7 AI7 RC7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 ...

Страница 8: ...ed test coverage You can verify the following for NI 9235 9236 modules measurement accuracy shunt calibration accuracy excitation voltage Measurement Accuracy Verification Complete the following steps to test the measurement accuracy of the device 1 Zero the calibrator with the ohms only zero OHMS ZERO operation Refer to the calibrator documentation for more information about zeroing the calibrato...

Страница 9: ...or the correct instance to use for polymorphic VIs LabVIEW Block Diagram NI DAQmx Function Call LabVIEW does not require this step Call DAQmxCreateTask with the following parameters taskName AIVerificationTask taskHandle taskHandle LabVIEW Block Diagram NI DAQmx Function Call Call DAQmxCreateAIVoltageChan WithExcit with the following parameters taskHandle taskHandle physicalChannel dev1 aix nameTo...

Страница 10: ... Start Task VI as shown in the following table LabVIEW Block Diagram NI DAQmx Function Call CallDAQmxCfgSampClkTiming with the following parameters taskHandle taskHandle source NULL rate 5000 sampleMode DAQmx_Val_FiniteSamps sampsPerChan 5000 LabVIEW Block Diagram NI DAQmx Function Call Call DAQmxSetAIBridgeShuntCal Enable with the following parameters taskHandle taskHandle channel NULL data FALSE...

Страница 11: ...es although you can save time by verifying only the values used in your application 14 Perform the following calculation for each test result value other than 0 V V using the results you recorded in step 11 Test Result 0 V V Test Result LabVIEW Block Diagram NI DAQmx Function Call Call DAQmxReadAnalogF64 with the following parameters taskHandle taskHandle numSampsPerChan 1 timeout 10 0 fillMode DA...

Страница 12: ...e DMM and 4 wire resistance measurement connections measure the resistance of the wire to be connected between the calibrator LO terminal and the module RC terminal and record the result for later use You must do this because this connection to the module creates a lead wire desensitization error This results in module readings that are systematically lower than the true shunt calibration output K...

Страница 13: ...or the correct instance to use for polymorphic VIs LabVIEW Block Diagram NI DAQmx Function Call LabVIEW does not require this step Call DAQmxCreateTask with the following parameters taskName SCVerificationTask taskHandle taskHandle LabVIEW Block Diagram NI DAQmx Function Call Call DAQmxCreateAIVoltageChan WithExcit with the following parameters taskHandle taskHandle physicalChannel dev1 aix nameTo...

Страница 14: ... Start Task VI as shown in the following table LabVIEW Block Diagram NI DAQmx Function Call CallDAQmxCfgSampClkTiming with the following parameters taskHandle taskHandle source NULL rate 5000 sampleMode DAQmx_Val_FiniteSamps sampsPerChan 10000 LabVIEW Block Diagram NI DAQmx Function Call Call DAQmxSetAIBridgeShuntCal Enable with the following parameters taskHandle taskHandle channel NULL data FALS...

Страница 15: ...following calculation using the results you recorded in step 11 ResultSCE ResultSCD 1 Rwire Rcomp where ResultSCE result with shunt calibration enabled ResultSCD result with shunt calibration disabled Rwire wire resistance measured in step 1 Rcomp 120 Ω for the NI 9235 and 350 Ω for the NI 9236 LabVIEW Block Diagram NI DAQmx Function Call Call DAQmxReadAnalogF64 with the following parameters taskH...

Страница 16: ...BY 18 Disconnect the calibrator from the device Excitation Voltage Verification The excitation source of the NI 9235 9236 is common to all eight input channels so you need to verify excitation voltage on only one channel Complete the following steps to verify the excitation voltage 1 Connect the positive input of the DMM to any EXC terminal of the module and the negative input of the DMM to any RC...

Страница 17: ...owing calibration specifications are for 23 5 C Table 2 NI 9235 9236 Measurement Accuracy Module Percent of Reading Gain Error Percent of Range Offset Error NI 9235 9236 0 04 max 0 002 max Range equals 29 4 mV V Table 3 NI 9235 9236 Shunt Calibration Accuracy Module Percent of Reading Gain Error NI 9235 0 22 max NI 9236 0 20 max Table 4 NI 9235 9236 Excitation Voltage Accuracy Module Accuracy NI 9...

Страница 18: ...For accuracy verification Upper Limits and Lower Limits are given in units of V V for verification and units of με for reference Table 5 NI 9235 Measurement Accuracy Verification Test Limits Calibrator Output Ω Nominal Value V V Nominal Value με 1 Year Limits Lower Limit V V Upper Limit V V Lower Limit με Upper Limit με 120 0 0 108 0 0263158 50 000 0 0263048 0 0263268 49 980 1 50 019 9 114 0 01282...

Страница 19: ...25 011 3 385 0 0238095 50 000 0 0237995 0 0238195 49 977 8 50 022 1 Note The Upper and Lower Limit V V values are commonly used for verification The Upper and Lower Limit με values are for reference Table 7 NI 9235 9236 Shunt Calibration Accuracy Verification Test Limits Module Nominal Value μV V Nominal Value με 1 Year Limits Lower Limit μV V Upper Limit μV V Lower Limit με Upper Limit με NI 9235...

Страница 20: ...NI Application Engineers National Instruments corporate headquarters is located at 11500 North Mopac Expressway Austin Texas 78759 3504 National Instruments also has offices located around the world to help address your support needs For telephone support in the United States create your service request at ni com support and follow the calling instructions or dial 512 795 8248 For telephone suppor...

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