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National Instruments 9235 Calibration Procedure Download Page 3

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National Instruments Corporation

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NI 9235/9236 Calibration Procedure

Documentation

You might find the following documentation helpful as you write the
calibration procedure:

•

NI-DAQmx Help

—This help file contains general information about

measurement concepts, key NI-DAQmx concepts, and common
applications that apply to all programming environments. To access
this help file, select

Start»All Programs»National Instruments»

NI-DAQ»NI-DAQmx Help

.

•

NI-DAQmx C Reference Help

—This help file contains C reference and

general information about measurement concepts. To access this help
file, select

Start»All Programs»National Instruments»NI-DAQ»

NI-DAQmx C Reference Help

.

•

DAQ Getting Started

guides for NI-DAQ 8.0 or later—This guide

describes how to install NI-DAQmx for Windows software and
NI-DAQmx-supported DAQ devices, and how to confirm 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/manual

s

.

•

NI 9235/9236 Operating Instructions and Specifications

—This

document describes how to use the NI 9235/9236 and includes
specifications and terminal assignments for the NI 9235/9236. The
limits you use to verify the accuracy of the devices are based on the
specifications found in this document. You can download the latest
version of this document from the NI Web site at

ni.com/manual

s

.

Calibration Interval

The NI 9235/9236 should be calibrated at a regular interval as defined by
the measurement accuracy requirements of your application. National
Instruments recommends that you routinely perform a complete calibration
at least once every year. You can shorten this interval based on the accuracy
demands of your application or requirements of your processes.

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Summary of Contents for 9235

Page 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...

Page 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...

Page 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...

Page 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...

Page 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 ...

Page 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...

Page 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 ...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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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