National Instruments 9205, 9206 Calibration Procedure

NI 9205/9206 Calibration Procedure

This document contains information about calibrating National Instruments 9205/9206 modules using NI-DAQmx. This calibration procedure is intended for metrology labs.

This document does not discuss programming techniques or compiler configuration. The NI-DAQmx driver contains online help files that have compiler-specific instructions and detailed function explanations. You can install these help files when you install NI-DAQmx on the calibration computer.

The NI 9205 and NI 9206 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 two years. You can shorten this interval based on the accuracy demands of your application or requirements of your processes. Self-calibration can be performed as needed or when the temperature varies by 5 °C or more from the last external calibration.

Contents

Conventions ............................................................................................ 2

Calibration Options ................................................................................. 3

Self-Calibration................................................................................ 3

External Calibration......................................................................... 3

Software and Documentation Requirements........................................... 3

Software ........................................................................................... 3

Documentation................................................................................. 4

Calibration Requirements .......................................................................5

Password .......................................................................................... 5

Test Equipment ................................................................................ 5

Test Conditions ................................................................................ 5

Calibration Process ................................................................................. 5

Calibration Process Overview ......................................................... 5

Initial Setup...................................................................................... 6

Self-Calibration................................................................................ 6

Verification Procedure......................................................................7

Adjustment Procedure ......................................................................10

AI Absolute Accuracy Tables and Formulas...........................................12

Device Test Limits...................................................................................13

Using the Table.................................................................................13

Range.........................................................................................13

Test Point...................................................................................14

2-Year Limits ............................................................................14

Where to Go for Support .........................................................................15

Conventions

The following conventions appear in this manual:

» The » symbol leads you through nested menu items and dialog box options

to a final action. The sequence File»Page Setup»Options directs you to pull down the File menu, select the Page Setup item, and select Options from the last dialog box.

This icon denotes a note, which alerts you to important information.

bold Bold text denotes items that you must select or click in the software, such

as menu items and dialog box options. Bold text also denotes parameter names and hardware labels.

italic Italic text denotes variables, emphasis, a cross-reference, or an introduction

to a key concept. Italic text also denotes text that is a placeholder for a word or value that you must supply.

monospace Monospace text denotes text or characters that you should enter from the

keyboard, sections of code, programming examples, and syntax examples. This font is also used for the proper names of disk drives, paths, directories, programs, subprograms, subroutines, device names, functions, operations, variables, filenames, and extensions.

NI 9205/9206 NI 9205/9206 refers to the NI 9205 and NI 9206.

NI 9205/9206 Calibration Procedure 2 ni.com

Calibration Options

The NI 9205/9206 support two types of calibration: self-calibration and external calibration.

Self-Calibration

Self-calibration, also known as internal calibration, uses a software command and requires no external connections. Self-calibration improves measurement accuracy by compensating for variables such as temperature that might have changed since the last external calibration. Self-calibration retains the traceability of the external calibration and can be performed as necessary to compensate for environmental changes.

External Calibration

External calibration is generally performed with a high-precision calibrator at either NI or a metrology lab. This procedure replaces all calibration constants in the EEPROM and is equivalent to a factory calibration at NI. Because the external calibration procedure changes all EEPROM constants, it invalidates the original calibration certificate. If an external calibration is done with a traceable signal generator source, a new calibration certificate can be issued. This document describes specific programming steps for writing an external calibration procedure for the NI 9205/9206.

Software and Documentation Requirements

This section describes the software and documentation required for both self-calibration and external calibration.

Software

Install NI-DAQmx 8.1 or later on the calibration computer. NI-DAQmx includes high-level function calls to simplify the task of writing software to calibrate devices. You must have the proper device driver installed on the calibration system before calibrating the device.

Note NI recommends that you install the NI-DAQmx driver software before physically

installing the NI 9205/9206. NI-DAQmx, available at and controls the NI 9205/9206.

NI-DAQmx supports a number of programming languages, including LabVIEW, LabWindows Visual Basic 6.0, Microsoft .NET, and Borland C++.

™

/CVI™, Microsoft Visual C++ 6.0, Microsoft

ni.com/downloads, configures

Documentation

You can access the NI-DAQmx header file, NIDAQmx.h, like any standard library. You can find examples of how to use the NI-DAQmx driver in the

Program Files\National Instruments\NI-DAQ\Examples

directory.

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 Guide 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/manuals.

• NI 9205 Operating Instructions/NI 9206 Operating Instructions—

These documents contain information about specific device features.

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

versions of these documents from the NI Web site at

manuals

ni.com/

NI 9205/9206 Calibration Procedure 4 ni.com

Calibration Requirements

Password

The default password for password-protected operations is NI.

Test Equipment

National Instruments recommends that you use the following equipment for calibrating the NI 9205/9206:

• Fluke 5700A calibrator. If that instrument is unavailable, use a high-precision voltage source with an accuracy of at least 10 ppm.

• NI cDAQ-9172 chassis.

Test Conditions

Follow these guidelines to optimize the connections and the environment:

• Keep connections to the device as short as possible. Long cables and wires act as antennae, picking up extra noise that 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 an ambient temperature of 23 ±10 °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 measurement circuitry is at a stable operating temperature.

Calibration Process

This section provides instructions for verifying and adjusting the NI 9205/9206.

Calibration Process Overview

The calibration process consists of the following steps:

1. Initial Setup—Configure the device in NI-DAQmx.

2. Self-Calibration—Measure the onboard reference voltage of the device and adjust the self-calibration constants.

3. Verification Procedure—Verify the existing operation of the device.

This step confirms whether the device was operating within its specified range prior to calibration.

Initial Setup

4. Adjustment Procedure—Perform an external calibration that adjusts the device calibration constants with respect to a known voltage source.

5. Perform another verification to ensure that the device operates within its specifications after adjustment.

The first four steps are explained in the following sections.

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 is in a nonhazardous location, the chassis power can be on when you install the module.

3. Insert the module into an available slot in the cDAQ-9172 chassis.

4. Launch MAX.

5. Right-click the device name and select Self-Test to ensure that the device is working properly.

Note When a device is configured with MAX, it is assigned a device name. Each function

call uses this device name to determine which DAQ device to calibrate. This document uses

dev1 to refer to the device name. In the following procedures, use the device name as it

appears in MAX.

Self-Calibration

Self-calibrate the device before completing the first verification, after the device has warmed up for the recommended time period. (DAQmx Self Calibrate VI), as shown in the following table, measures the onboard reference voltage of the device and adjusts the self-calibration constants to account for any errors caused by short-term fluctuations in the operating environment. When you self-calibrate a device, no external signal connections are necessary.

NI-DAQmx Function Call LabVIEW Block Diagram

DAQmxSelfCal

Call DAQmxSelfCal with the following parameters:

deviceName:

NI 9205/9206 Calibration Procedure 6 ni.com

dev1

Verification Procedure

Verification determines how well the device is meeting its specifications. By completing this procedure, you can see how the device has drifted over time, which helps you determine the appropriate calibration interval for your application. Table 4 in the Device Test Limits section shows all acceptable settings for the device type. Throughout the verification process, use Table 4 to determine if the device is operating within its specified range prior to calibration. Because the NI 9205/9206 has many different ranges, you must verify measurements for each available range on these modules.

Complete the following steps to test the performance of the device:

1. Refer to Table 1 for a list of the NI connection accessories for the NI 9205/9206 and instructions on connecting the calibrator to the device.

Table 1. NI Connection Accessories

Device Connection Accessory Connection Instructions

NI 9205/9206 NI 9940 36-position strain

relief & high voltage connector kit

NI 9205 with DSUB

NI 9933 37-pin connector kit, screw terminal connector and DSUB shell

2. Set the calibrator voltage to the Test Point value indicated in Table 4. NI recommends that you verify all values, although you can save time by verifying only the values used in your application.

3. If you use C function calls, create a task using shown in the following table. If you use LabVIEW, skip this step. The task is created in step 4 in LabVIEW.

Connect the positive output of the calibrator to AI0 (pin 1) and the negative output of the calibrator to AI8 (pin 19) and COM (pin 17). If the calibrator has a guard connection, connect that terminal to COM instead of connecting COM to the negative output.

Connect the positive output of the calibrator to AI0 (pin 1) and the negative output of the calibrator to AI8 (pin 20) and COM (pin 10). If the calibrator has a guard connection, connect that terminal to COM instead of connecting COM to the negative output.

DAQmxCreateTask, as

NI-DAQmx Function Call LabVIEW Block Diagram

Call DAQmxCreateTask with the following parameters:

taskName:

AIVerificationTask

taskHandle: &taskHandle

LabVIEW does not require this step.

4. Create and configure an AI voltage channel through NI-DAQmx using

DAQmxCreateAIVoltageChan (DAQmx Create Virtual Channel

VI), as shown in the following table. Use Table 4 to determine the minimum and maximum values for the device.

NI-DAQmx Function Call LabVIEW Block Diagram

Call DAQmxCreateAIVoltageChan with the following parameters:

taskHandle:

taskHandle

physicalChannel: dev1/ai0 nameToAssignToChannel:

myVoltageChannel

terminalConfig:

DAQmx_Val_Cfg_Default

minVal: maxVal:

–10.0

10.0

units: DAQmx_Val_Volts customScaleName: NULL

5. Configure the timing properties for the voltage acquisition using

DAQmxCfgSampClkTiming (DAQmx Timing VI), as shown in the

following table.

NI-DAQmx Function Call LabVIEW Block Diagram

Call DAQmxCfgSampClkTiming with the following parameters:

taskHandle:

taskHandle

source: NULL rate: 100000.0 activeEdge:

DAQmx_Val_Rising

sampleMode:

DAQmx_Val_FiniteSamps

sampsPerChan: 10000

NI 9205/9206 Calibration Procedure 8 ni.com

6. Start the acquisition using DAQmxStartTask (DAQmx Start Task VI), as shown in the following table.

NI-DAQmx Function Call LabVIEW Block Diagram

Call DAQmxStartTask with the following parameter:

taskHandle:

taskHandle

7. Acquire 10,000 points of voltage data using DAQmxReadAnalogF64 (DAQmx Read VI), as shown in the following table.

NI-DAQmx Function Call LabVIEW Block Diagram

Call DAQmxReadAnalogF64 with the following parameters:

taskHandle:

taskHandle

numSampsPerChan: –1 timeout: 10.0 fillMode:

DAQmx_Val_GroupByChannel

readArray: data arraySizeInSamples: 10000 sampsPerChanRead: &read reserved: NULL

8. Average the voltage values that you acquired. Compare the resulting average to the Upper Limit and Lower Limit values in Table 4. If the result is between these values, the device passes the test.

9. Clear the acquisition using

DAQmxClearTask (DAQmx Clear Task

VI), as shown in the following table.

NI-DAQmx Function Call LabVIEW Block Diagram

Call DAQmxClearTask with the following parameter:

taskHandle:

taskHandle

10. Repeat steps 3 through 9 for all ranges and all values.

11. Disconnect the calibrator from the device or proceed to the Adjustment

Procedure section to adjust the analog input calibration constants.

Adjustment Procedure

The NI 9205/9206 adjustment procedure adjusts the analog input calibration constants. At the end of each adjustment procedure, the new constants are stored in the external calibration area of the device EEPROM. These values are password-protected, which ensures that you do not accidentally access or modify any calibration constants adjusted by the metrology laboratory. The default password is

Complete the following steps to adjust the device with a calibrator:

1. Refer to Table 1 for a list of the NI connection accessories for the

2. Set the calibrator to output 4.0 V.

NI.

NI 9205/9206 and instructions on connecting the calibrator to the device.

3. Open a calibration session on the device using (DAQmx Initialize External Calibration VI), as shown in the following table.

NI-DAQmx Function Call LabVIEW Block Diagram

Call DAQmxInitExtCal with the following parameters:

deviceName:

dev1

password: NI calHandle: &calHandle

DAQmxInitExtCal

NI 9205/9206 Calibration Procedure 10 ni.com

4. Perform an external adjustment using DAQmxMSeriesCalAdjust (DAQmx Adjust M-Series Calibration VI), as shown in the following table.

NI-DAQmx Function Call LabVIEW Block Diagram

Call

DAQmxMSeriesCalAdjust

with the following parameters:

calHandle:

calHandle

referenceVoltage: 4.0

5. Save the adjustment to the EEPROM using

DAQmxCloseExtCal

(DAQmx Close External Calibration), as shown in the following table. This function also saves the date, time, and temperature of the adjustment to the onboard memory.

Note If the device fails the calibration procedure, no constants are written to the

EEPROM.

NI-DAQmx Function Call LabVIEW Block Diagram

Call DAQmxCloseExtCal with the following parameters:

calHandle:

calHandle

action: DAQmx_Val_

Action_Commit

6. Disconnect the calibrator from the device.

The device is now calibrated with respect to the external source. After calibrating the device, verify the analog input operation by repeating the

Verification Procedure section.

AI Absolute Accuracy Tables and Formulas

The values in the following tables are based on calibrated scaling coefficients, which are stored in the onboard EEPROM. The following calibration specifications are for 23 ±10 °C.

Table 2. Accuracy Summary

Nominal Range (V)

Absolute Accuracy

at Full Scale

(μV)

Random Noise,

σ (μVrms)

Sensitivity2 (μV)

±10 3230 240 96.0

±5 1730 116 46.4

±1 390 26 10.4

±0.2 114 10 4.0

Absolute accuracy values at full scale on the analog input channels assume the device is operating within 10 °C of the last external calibration and are valid for averaging 100 samples immediately following internal calibration.

Sensitivity is the smallest voltage change that can be detected. It is a function of noise.

Table 3. Accuracy Details

Nominal

Range (V)

Residual

Gain

Error

(ppm of

Reading)

Gain

Tempco

(ppm/°C)

Reference

Tempco

Residual

Offset Error

(ppm of

Range)

Offset Tempco (ppm of

Range/°C)

I N L E r r o r

(ppm of

Range)

±10 115 11 5 20 44 76

±5 135 11 5 20 47 76

±1 155 11 5 25 66 76

±0.2 215 11 5 40 162 76

NI 9205/9206 Calibration Procedure 12 ni.com

AbsoluteAccuracy = Reading · (GainError) + Range · (OffsetError) + NoiseUncertainty

GainError = ResidualAIGainError + GainTempco · (TempChangeFromLastInternalCal) + ReferenceTempco · (TempChangeFromLastExternalCal)

OffsetError = ResidualAIOffsetError + OffsetTempco · (TempChangeFromLastInternalCal) + INL_Error

Noise Uncertainty = RandomNoise · 3 / for a coverage factor of 3

10000

10000 points

ResidualAIGainError = ErrorRelativetoExternalRef

CalibrationInterval

years

+ ReferenceDriftOverTime

ppm

GainTempco = AnalogCircuitryGainTempco

ReferenceTempco = ReferenceDriftOverTime

ResidualOffsetError = OffsetErrorDueToCalibration

ppm

OffsetTempco = PreGainOffsetTempcoμV / RangeV + PostGainOffsetTempco

INL_Error = 2 · ADC_Dithered_INL

RandomNoise = RandomNoise

μVrms

Device Test Limits

Σ and averaging

ppm_per_year

Table 4 lists the specifications that the NI 9205/9206 meets if it has been two years between calibrations.

Using the Table

The following definitions describe how to use the information from Table 4.

Range

Range refers to the minimum or maximum voltage range of an input signal.

Test Point

The Test Point is the voltage value that is input or output for verification purposes. This value is broken down into two columns—Location and

Value. Location refers to where the test value fits within the test range. Value refers to the voltage value to be verified. Max refers to maximum value, Min refers to minimum value, and Mid refers to mid-scale.

2-Year Limits

The 2-Year Limits column contains the Upper Limits and Lower Limits for the test point value. That is, when the device is within its 2-year calibration interval, the test point value should fall between these upper and lower limit values.

Table 4. NI 9205/9206 Analog Input Values

Range (V) Tes t Po int 2-Year Limits

Minimum Maximum Location Val ue (V ) Lower Limit (V) Upper Limit (V)

–10 10 Max 9.980000 9.976836 9.983164

–10 10 Mid 0.000000 –0.001407 0.001407

–10 10 Min –9.980000 –9.983164 –9.976836

–5 5 Max 4.990000 4.988303 4.991697

–5 5 Mid 0.000000 –0.000718 0.000718

–5 5 Min –4.990000 –4.991697 – 4.988303

–1 1 Max 0.998000 0.997617 0.998383

–1 1 Mid 0.000000 –0.000168 0.000168

–1 1 Min –0.998000 –0.998383 –0.997617

–0.200 0.200 Max 0.199600 0.199489 0.199711

–0.200 0.200 Mid 0.000000 –0.000056 0.000056

–0.200 0.200 Min –0.199600 –0.199711 –0.199489

NI 9205/9206 Calibration Procedure 14 ni.com

Where to Go for Support

The National Instruments Web site is your complete resource for technical support. At troubleshooting and application development self-help resources to email and phone assistance from 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 instructions or dial 512 795 8248. For telephone support outside the United States, contact your local branch office:

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National Instruments 9205, 9206 Calibration Procedure

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