NI 9213 Calibration Procedure

NI 9213 Calibration Procedure
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This document contains information about calibrating National
Instruments 9213 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.
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
Verification Procedure ..................................................................... 6
Analog Input Gain Verification ................................................ 6
Analog Input Offset Verification.............................................. 10
Specifications .......................................................................................... 14
Test Limits .............................................................................................. 14
Range ............................................................................................... 14
Test Point ......................................................................................... 14
1-Year Limits ................................................................................... 14
Where to Go for Support......................................................................... 16
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.
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 8.9.5 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.
NI recommends that you install the NI-DAQmx driver software before physically
installing the NI 9213. NI-DAQmx, available at ni.com/downloads, configures and
controls the NI 9213.
Note
NI-DAQmx supports a number of programming languages, including
LabVIEW, LabWindows™/CVI™, Microsoft Visual C++ 6.0, Microsoft
Visual Basic 6.0, Microsoft .NET, and Borland C++.
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.
NI 9213 Calibration Procedure
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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 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.
The documents above are installed with NI-DAQmx. You can also download the
latest versions from the NI Web site at ni.com/manuals.
Note
•
NI 9213 Operating Instructions and Specifications—This document
describes how to use the NI 9213 and include specifications and
terminal assignments for the NI 9213. The limits you use to verify the
accuracy of the device 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/manuals.
Calibration Interval
The NI 9213 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.
© National Instruments Corporation
3
NI 9213 Calibration Procedure
Test Equipment
National Instruments recommends that you use the following equipment
for calibrating the NI 9213.
Table 1. Recommended Equipment
Equipment
Recommended Model
Requirements
Calibrator
Fluke 5520A using the 3.3 V range∗
If this instrument is unavailable, use a
high-precision voltage source with an
accuracy of at least 40 ppm and an output
impedance of less than or equal to 3.125 Ω.†
Chassis
NI cDAQ-9172
*
—
Because the 3.3 V range has a low output impedance.
†
This output impedance assumes 16 channels are connected to the calibrator. If you are connecting less than 16 channels to
the calibrator, you can calculate the output impedance for the calibrator using the following equation:
CalOutMax = (50 Ω/Ch) – Rlead
where
CalOutMax is the maximum calibrator output impedance allowed to properly calibrate the NI 9213
Ch is the number of channels connected to the calibrator
Rlead is the resistance of the cable connecting the calibrator to the NI 9213
Test Conditions
Follow these guidelines to optimize the connections and the environment:
NI 9213 Calibration Procedure
•
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 15 minutes to ensure that the measurement
circuitry is at a stable operating temperature.
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Calibration Procedure
This section provides instructions for verifying the performance of the
NI 9213.
Calibration Process Overview
The calibration process consists of the following steps:
1.
Initial Setup—Configure the device in NI-DAQmx.
2.
Verification Procedure—Verify the existing operation of the device.
This step confirms whether the device is operating within its specified
range and whether it needs adjustment.
3.
Adjustment—If the device does not fall within the desired
specifications, submit the device to NI for a factory calibration to
adjust the calibration constants.
4.
Verification Procedure—Perform another verification to ensure that
the device 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 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.
© National Instruments Corporation
5
NI 9213 Calibration Procedure
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. Tables 3 and 4 in the Test Limits section show all
acceptable settings for the device type. Throughout the verification process,
use Tables 3 and 4 to determine if the device is operating within its
specified range. You must perform verification on all analog input
channels.
Analog Input Gain Verification
Complete the following steps to test the performance of the analog input
gain of the device:
1.
Connect the LO output of the calibrator to all negative terminals of the
NI 9213, then connect the HI output of the calibrator to all positive
terminals. Refer to Figure 1 for the terminal assignments of the
NI 9213.
NC
TC0+
TC1+
TC2+
TC3+
TC4+
TC5+
TC6+
TC7+
TC8+
TC9+
TC10+
TC11+
TC12+
TC13+
TC14+
TC15+
COM
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
NC
TC0–
TC1–
TC2–
TC3–
TC4–
TC5–
TC6–
TC7–
TC8–
TC9–
TC10–
TC11–
TC12–
TC13–
TC14–
TC15–
COM
Figure 1. NI 9213 Terminal Assignments
NI 9213 Calibration Procedure
2.
When using the Fluke 5520A, lock the calibrator range to 3.3 V to
maintain a low output impedance.
3.
Set the calibrator voltage to a Test Point value indicated in Table 3.
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4.
If you use C function calls, create a task using DAQmxCreateTask, as
shown in the following table. If you use LabVIEW, skip this step. The
task is created in step 5 in LabVIEW.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxCreateTask with
the following parameters:
LabVIEW does not require this step.
taskName:
AIVerificationTask
taskHandle: &taskHandle
5.
Create and configure an AI voltage channel using the DAQmx Create
Virtual Channel VI, as shown in the following table.
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.
Note
LabVIEW Block Diagram
NI-DAQmx Function Call
Call
DAQmxCreateAIVoltageChan
with the following parameters:
taskHandle: taskHandle
physicalChannel: dev1/aiX*
nameToAssignToChannel:
myVoltageChannel
terminalConfig:
DAQmx_Val_Cfg_Default
minVal: –0.078125
maxVal: 0.078125
units: DAQmx_Val_Volts
customScaleName: NULL
*
X refers to the channel number.
© National Instruments Corporation
7
NI 9213 Calibration Procedure
6.
Set the timing mode using the DAQmx Channel Property Node, as
shown in the following table. Use Table 3 to determine when to set the
timing mode to High Resolution or High Speed.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxSetChanAttribute
with the following parameters:
taskHandle: taskHandle
Attribute:
DAQmx_AI_ADCTimingMode
Value:
DAQmx_Val_HighResolution
or DAQmx_Val_HighSpeed
7.
Configure the timing properties for the voltage acquisition using the
DAQmx Timing VI, as shown in the following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxCfgSampClkTiming
with the following parameters:
taskHandle: taskHandle
source: NULL
rate: 8.9 (High Resolution),
100 (High Speed)
activeEdge:
DAQmx_Val_Rising
sampleMode:
DAQmx_Val_FiniteSamps
sampsPerChan:
50 (High Resolution),
200 (High Speed)
NI 9213 Calibration Procedure
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8.
Enable autozero using the DAQmx Channel Property Node, as shown
in the following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxSetChanAttribute
with the following parameters:
taskHandle: taskHandle
Attribute:
DAQmx_AI_AutoZeroMode
Value (Autozero on):
DAQmx_Val_EverySample
9.
Start the acquisition using the DAQmx Start Task VI, as shown in the
following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxStartTask with the
following parameter:
taskHandle: taskHandle
10. Acquire the voltage data using the DAQmx Read VI, as shown in the
following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxReadAnalogF64 with
the following parameters:
taskHandle: taskHandle
numSampsPerChan: –1
timeout: 10.0
fillMode:
DAQmx_Val_GroupByChannel
readArray: data
arraySizeInSamples:
50 (High Resolution),
200 (High Speed)
sampsPerChanRead: &read
reserved: NULL
© National Instruments Corporation
9
NI 9213 Calibration Procedure
11. Average the voltage values that you acquired. Compare the resulting
average to the Upper Limit and Lower Limit values in Table 3. If the
result is between these values, the device passes the test.
12. Clear the acquisition using the DAQmx Clear Task VI, as shown in the
following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxClearTask with the
following parameter:
taskHandle: taskHandle
13. Repeat steps 3 through 12 for all channels and all Test Point values.
NI recommends that you verify all values, although you can save time
by verifying only the values used in your application.
14. Disconnect the calibrator from the device.
Analog Input Offset Verification
Complete the following steps to test the performance of the analog input
offset of the device:
1.
Use copper wires to connect the positive and negative terminals of each
channel on the NI 9213 to each other. Wire TC0+ to TC0–, TC1+ to
TC1–, and so on. Refer to Figure 1 for the terminal assignments of the
NI 9213.
2.
If you use C function calls, create a task using DAQmxCreateTask, as
shown in the following table. If you use LabVIEW, skip this step. The
task is created in step 3 in LabVIEW.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxCreateTask with
the following parameters:
LabVIEW does not require this step.
taskName:
AIVerificationTask
taskHandle: &taskHandle
NI 9213 Calibration Procedure
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3.
Create and configure an AI voltage channel using the DAQmx Create
Virtual Channel VI, as shown in the following table.
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.
Note
LabVIEW Block Diagram
NI-DAQmx Function Call
Call
DAQmxCreateAIVoltageChan
with the following parameters:
taskHandle: taskHandle
physicalChannel: dev1/aiX*
nameToAssignToChannel:
myVoltageChannel
terminalConfig:
DAQmx_Val_Cfg_Default
minVal: –0.078125
maxVal: 0.078125
units: DAQmx_Val_Volts
customScaleName: NULL
*
X refers to the channel number.
4.
Set the timing mode using the DAQmx Channel Property Node, as
shown in the following table. Set the timing mode to
High Resolution or High Speed, depending on which timing
mode you are testing.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxSetChanAttribute
with the following parameters:
taskHandle: taskHandle
Attribute:
DAQmx_AI_ADCTimingMode
Value:
DAQmx_Val_HighResolution
or DAQmx_Val_HighSpeed
© National Instruments Corporation
11
NI 9213 Calibration Procedure
5.
Configure the timing properties for the voltage acquisition using the
DAQmx Timing VI, as shown in the following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxCfgSampClkTiming
with the following parameters:
taskHandle: taskHandle
source: NULL
rate: 8.9 (High Resolution),
100 (High Speed)
activeEdge:
DAQmx_Val_Rising
sampleMode:
DAQmx_Val_FiniteSamps
sampsPerChan:
50 (High Resolution),
200 (High Speed)
6.
Enable autozero using the DAQmx Channel Property Node, as shown
in the following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxSetChanAttribute
with the following parameters:
taskHandle: taskHandle
Attribute:
DAQmx_AI_AutoZeroMode
Value (Autozero on):
DAQmx_Val_EverySample
7.
Start the acquisition using the DAQmx Start Task VI, as shown in the
following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxStartTask with the
following parameter:
taskHandle: taskHandle
NI 9213 Calibration Procedure
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8.
Acquire the voltage data using the DAQmx Read VI, as shown in the
following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxReadAnalogF64 with
the following parameters:
taskHandle: taskHandle
numSampsPerChan: –1
timeout: 10.0
fillMode:
DAQmx_Val_GroupByChannel
readArray: data
arraySizeInSamples:
50 (High Resolution),
200 (High Speed)
sampsPerChanRead: &read
reserved: NULL
9.
Average the voltage values that you acquired. Compare the resulting
average to the Upper Limit and Lower Limit values in Table 4 for the
timing mode you selected previously. If the result is between these
values, the device passes the test.
10. Clear the acquisition using the DAQmx Clear Task VI, as shown in the
following table.
LabVIEW Block Diagram
NI-DAQmx Function Call
Call DAQmxClearTask with the
following parameter:
taskHandle: taskHandle
11. Repeat steps 2 through 10 for all channels and both timing modes.
NI recommends that you verify all values, although you can save time
by verifying only the values used in your application.
© National Instruments Corporation
13
NI 9213 Calibration Procedure
Specifications
The values in the following table are based on calibrated scaling
coefficients, which are stored in the onboard EEPROM. The following
calibration specifications are for 23 ±10 °C.
Table 2. NI 9213 Accuracy
*
Timing Mode
Percent of Reading (Gain Error)
Percent of Range* (Offset Error)
High Resolution
0.044% max
0.008% (6 μV) max
High Speed
0.051% max
0.022% (17 μV) max
Range equals 78.125 mV.
Test Limits
Tables 3 and 4 list the specifications that the NI 9213 should meet if it has
been one year between calibrations. The following definitions describe
how to use the information from Tables 3 and 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.
1-Year Limits
The 1-Year Limits column contains the Upper Limits and Lower Limits for
the test point value. That is, when the device is within its 1-year calibration
interval, the test point value should fall between these upper and lower limit
values.
NI 9213 Calibration Procedure
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Table 3. NI 9213 Gain Verification Test Limits
Range (V)
Timing
Mode
Test Point
1-Year Limits
Minimum
Maximum
Location
Value (V)
Lower
Limit (V)
Upper
Limit (V)
High
Resolution
–0.078125
0.078125
Max
0.070000
0.069963
0.070037
High
Resolution
–0.078125
0.078125
Min
–0.070000
–0.070037
–0.069963
High Speed
–0.078125
0.078125
Max
0.070000
0.069947
0.070053
High Speed
–0.078125
0.078125
Min
–0.070000
–0.070053
–0.069947
Table 4. NI 9213 Offset Verification Test Limits
Range (V)
Timing
Mode
Test Point
1-Year Limits
Minimum
Maximum
Location
Value (V)
Lower
Limit (V)
Upper
Limit (V)
High
Resolution
–0.078125
0.078125
Mid
0.000000
–0.000006
0.000006
High Speed
–0.078125
0.078125
Mid
0.000000
–0.000017
0.000017
© National Instruments Corporation
15
NI 9213 Calibration Procedure
Where to Go for Support
The National Instruments Web site is your complete resource for technical
support. At ni.com/support you have access to everything from
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 ni.com/support and follow the calling
instructions or dial 512 795 8248. For telephone support outside the United
States, contact your local branch office:
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United Kingdom 44 (0) 1635 523545
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