CALIBRATION PROCEDURE
SCXI -1520
™
This document contains information and step-by-step instructions for
calibrating the National Instruments SCXI-1520 module.
Equipment and Other Test Requirements
This section describes the equipment, software, documentation, and test
conditions required for calibrating the SCXI-1520.
Test Equipment
Calibration requires a high-precision voltage source with at least 50 ppm
accuracy, a multiranging 5 1/2 digit digital multimeter (DMM) with
15 ppm accuracy, and a 16-bit data acquisition (DAQ) device.
NI recommends the following instruments for calibrating the SCXI-1520.
•
Calibrator—Fluke 5700A
•
DMM—NI 4060 or Agilent 34401A
•
16-bit DAQ device
If these instruments are not available, use the accuracy requirements listed
above to select a substitute calibration standard.
If you do not have custom connection hardware, you need an SCXI-1314 terminal
block and a shielded 68-pin connector cable. These components give easy access to the
individual pins on the SCXI-1520 front connectors. You also need an SCXI-1349 cable
adapter to connect the SCXI-1520 to the DAQ device.
Note
Software and Documentation
Use the following software and documentation to calibrate the SCXI-1520.
You can find them on the NI Web site at ni.com/support.
•
The latest version of the NI-DAQ driver software
•
NI-DAQ Function Reference Help
•
NI-DAQ User Manual for PC Compatibles
•
SCXI-1314 Installation Guide
•
SCXI-1349 Installation Guide
Software
The SCXI-1520 calibration procedure requires the latest version of the
NI-DAQ driver on the calibration system. The driver supports a number
of programming languages, including LabVIEW, Measurement Studio,
Microsoft Visual C++, Microsoft Visual Basic, and Borland C++. When
you install the driver, you need to install support only for the programming
language you are using.
Documentation
The NI-DAQ Function Reference Help and the NI-DAQ User Manual for
PC Compatibles contain detailed information on using the NI-DAQ driver.
The online help includes detailed information on the driver functions.
You can access the help by selecting Start»Programs»National
Instruments DAQ»NI-DAQ Help. The user manual provides instructions
on installing and configuring DAQ devices. The user manual also includes
detailed information on creating applications that use the NI-DAQ driver.
These are your primary references for writing your calibration utility. For
more information on the SCXI-1520, refer to the SCXI-1520 User Manual.
Test Conditions
Follow these guidelines to optimize the connections and the environment
during calibration.
SCXI-1520 Calibration Procedure
•
Keep connections to the SCXI module short. Long cables and wires act
as antennae, picking up extra noise and thermal offsets that can affect
measurements.
•
Use shielded copper wire for all cable connections to the device.
Use twisted-pair wire to reduce noise.
•
Maintain the temperature between 18 and 28 °C.
•
Keep relative humidity below 80%.
•
Allow a warm-up time of at least 15 minutes for the SCXI module
and 30 minutes for the DAQ device to ensure that the measurement
circuitry is at a stable operating temperature.
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Calibration
The calibration process consists of the following steps:
1.
Setting up the device for testing.
2.
Verifying the existing operation of the device to determine whether
it is operating within its specifications.
3.
Adjusting the device with respect to a known voltage source.
4.
Verifying that the device is operating within its specifications after
adjustments.
Setting Up the SCXI-1520 for Testing
Complete the following steps to set up the SCXI-1520 for testing.
1.
Install the SCXI-1520 in slot 1 of the SCXI chassis.
2.
Using an SCXI-1349 cable adapter, connect a 68-to-68-pin cable
between the SCXI-1520 module and the DAQ device installed in the
host computer, as shown in Figure 1.
8
1
7
2
®
5
4
3
2
1
ADDRESS
3
6
SC
XI
11
00
4
5
1
2
3
4
DAQ Device
SH68-68 Cable
SCXI-1349 Cable Adapter
Thumbscrews
5
6
7
8
SCXI-1520 Module
SCXI-1314 Terminal Block
SCXI Chassis Power Switch
SCXI-1000 Chassis
Figure 1. Connecting an SCXI Chassis to a DAQ Device
© National Instruments Corporation
3
SCXI-1520 Calibration Procedure
3.
Configure the hardware with Measurement & Automation Explorer
(MAX). For more information on configuring the system, refer to the
documentation for the DAQ device and the SCXI-1520.
Verifying Gain and Offset Errors
The verification procedure determines how well the SCXI-1520 module
is meeting its specifications. You can use this information to select the
appropriate calibration interval for your application.
Complete the following steps to verify gain and offset errors of the
SCXI-1520.
1.
Read the Test Conditions section.
2.
Refer to the specifications in Table 2.
3.
Call Calibrate_E_Series to minimize the uncertainty associated
with the DAQ device measurements. Set the following parameters:
4.
5.
SCXI-1520 Calibration Procedure
•
deviceNumber—The value assigned by MAX
•
calOP—ND_SELF_CALIBRATE
•
setOfCalConst—ND_USER_EEPROM_AREA
•
calRefVolts—0.0
Call AI_Configure to put the DAQ device in bipolar mode. Set the
following parameters:
•
deviceNumber—The value assigned by MAX
•
chan—0
•
inputMode—0
•
inputRange—0
•
polarity—0
•
driveAIS—0
Call SCXI_Track_Hold_Setup to set up the track-and-hold circuitry
of the SCXI-1520. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
inputMode—2
•
source—0
•
send—0
•
holdCount—1
•
DAQdeviceNumber—The value assigned by MAX
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6.
Call SCXI_MuxCtr_Setup to configure the DAQ device counter for
use as a multiplexer counter during SCXI channel scanning. Set the
following parameters:
•
deviceNumber—The value assigned by MAX
•
enable—1
•
scanDiv—1
•
ctrValue—1
7.
Connect the calibrator to the appropriate analog input, starting
with channel 0. Refer to Table 1 to determine which pins on the 96-pin
front connector correspond to the positive and negative inputs of the
specified channel. For example, the positive input for channel 0 (S0+)
is pin C32. The negative input for channel 0 (S0–) is pin B32. If you
are using an SCXI-1314 terminal block, connect the calibrator to the
S0+ and S0– inputs.
8.
Call SCXI_SCAN_Setup to set up the SCXI chassis to perform a
multiplexed scanning data acquisition. Set the following parameters:
9.
•
SCXIchassisID—The value assigned by MAX
•
numModules—1
•
moduleList—{1}1
•
numChans—{1}
•
startChans—{The channel number from step 7}
•
DAQdeviceNumber—The value assigned by MAX
•
modeFlag—0
Call SCXI_Configure_Filter to configure the filter on the module.
Set the following parameters:
•
chassisID—The value assigned by MAX
•
moduleSlot—1
•
channel—The channel number from step 7
•
filterMode—0
•
freq—0
•
cutoffDivDown—0
•
outClkDivDown—0
10. Call SCXI_Set_Potentiometer to set the fine potentiometer to the
center position. Set the following parameters:
1
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
Array notation: {X} denotes a one-element array initialized with the value X; [Y] denotes an uninitialized array of size Y.
© National Instruments Corporation
5
SCXI-1520 Calibration Procedure
•
channel—The channel number from step 7
•
value—2048
•
pottype—1
11. Call SCXI_Set_Potentiometer to set the coarse potentiometer
to the center position. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
channel—The channel number from step 7
•
value—62
•
pottype—0
12. Call SCXI_Set_Excitation to set the excitation voltage to zero.
Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
moduleChan—The channel number from step 7
•
excitationType—2
•
excitationValue—0
SCXI_Set_Excitation returns a 32-bit floating-point number,
actualExcitationValuePtr.
13. Call SCXI_Configure_Connection to configure the channel for
a full-bridge connection. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
moduleChan—The channel number from step 7
•
connectionType—6
14. Call SCXI_Set_Gain to set the gain you want to test on the module.
Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
channel—The channel number from step 7
•
gain—The gain value you want to test; you can find valid gain
values in Table 2.
15. Set the calibrator to output the test point voltage from Table 2.
16. Call SCAN_Op to acquire the data. Set the following parameters:
SCXI-1520 Calibration Procedure
•
deviceNumber—The value assigned by MAX
•
numChans—{1}
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•
chans—{0}
•
gains—1
•
buffer—[5000]
•
count—5000
•
sampleRate—10000
•
scanRate—5000
17. Call SCXI_Scale to scale the data returned by SCAN_Op. Set the
following parameters:
•
SCXIChassisID—The value assigned by MAX
•
moduleSlot—1
•
channel—The channel number from step 7
•
SCXIgain—The gain value from step 14
•
TBgain—1
•
DAQboard—The device number of the DAQ device
•
DAQchannel—0
•
DAQgain—1
•
numPoints—5000
•
binArray—The array returned by SCAN_Op in step 16
The result is a set of scaled voltages called scaledArray.
18. Average the results returned by SCXI_Scale. Compare the averaged
result to the upper and lower limits in Table 2. If the result falls within
these limits, your module has passed this portion of the test. If the
result is outside these limits, adjust the module using the steps in the
Adjusting for Gain, Offset, and Excitation Errors section.
19. Repeat steps 14 through 18 for the remaining gains.
20. Repeat steps 7 through 19 for the remaining channels.
If all channels fall within the upper and lower limits, the gain and offset do not need
adjustment.
Note
Verifying Voltage Excitation
This section describes how to verify the voltage excitation of the
SCXI-1520 and how to calculate new voltage excitation constants.
The calibration constants for the voltage excitation on the SCXI-1520
are calculated with respect to the onboard 2.5 V reference voltage. These
calibration constants are stored on the module EEPROM and can be read
by application software and used for software correction. You cannot
physically adjust the excitation on the SCXI-1520. If the measured values
of the excitation fall outside the limits given in Table 3, the module is not
© National Instruments Corporation
7
SCXI-1520 Calibration Procedure
operating within specifications. Return it to NI for repair. For more
information about how to contact NI for repair, refer to the Signal
Conditioning Technical Support Information document.
1.
Read the Test Conditions section.
2.
Connect the DAQ device to the SCXI-1520 using an SCXI-1349 cable
adapter and a 68-to-68-pin cable.
3.
Connect the DMM to the appropriate excitation output terminals,
starting with channel 0. Refer to Table 1 to determine which pins
on the 96-pin front connector correspond to the positive and negative
excitation terminals of the specified channel. For example, the positive
excitation terminal for channel 0 (P0+) is pin C30. The negative
excitation terminal for channel 0 (P0–) is pin B30. If you are using
an SCXI-1314 terminal block, connect the DMM to the P0+ and P0–
output terminals of the SCXI-1314.
4.
Call SCXI_Set_Excitation to set the excitation voltage to the
desired value. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
moduleChan—The channel number from step 3
•
excitationType—2
•
excitationValue—The excitation value that you want to measure.
Refer to Table 3 for a list of valid values.
SCXI_Set_Excitation returns a 32-bit floating-point number
called actualExcitationValuePtr. This number was stored in the
SCXI-1520 EEPROM when the module was last calibrated, and
represents the voltage excitation measured at that time. Record this
value as Vexe.
SCXI-1520 Calibration Procedure
5.
Read the voltage from the DMM and record it as Vexm. You will use
Vexm to verify the voltage excitation and, if necessary, to calculate new
calibration constants in the Adjusting Calibration Constants section.
6.
Compare Vexm from step 5 to the upper and lower limits in Table 2.
If Vexm is within these limits, the module has passed this portion of the
test. If Vexm is outside these limits, the module is not operating within
specifications. Return it to NI for repair.
7.
Divide Vexe from step 4 by Vexm from step 5. If the resulting value is
between 0.999 and 1.001, the calibration constants are within the
required specifications. Do not use 0.0 V excitation for this step.
8.
Repeat steps 4 through 7 for the remaining excitation levels you want
to test on the module.
9.
Repeat steps 3 through 8 for the remaining channels you want to test
on the module.
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Adjusting for Gain, Offset, and Excitation Errors
The Determining Gain Errors and Adjusting Calibration Constants
sections explain how to determine the gain, offset, and excitation errors of
the SCXI-1520 and how to adjust the calibration constants to correct for
these errors.
Determining Gain Errors
Complete the following steps to determine the gain errors of the
SCXI-1520.
1.
Read the Test Conditions section.
2.
Refer to the specifications in Table 2.
3.
Call Calibrate_E_Series to minimize the uncertainty associated
with the DAQ device measurements. Set the following parameters:
4.
5.
© National Instruments Corporation
•
deviceNumber—The value assigned by MAX
•
calOP—ND_SELF_CALIBRATE
•
setOfCalConst—ND_USER_EEPROM_AREA
•
calRefVolts—0.0
Call AI_Configure to put the DAQ device in bipolar mode. Set the
following parameters:
•
deviceNumber—The value assigned by MAX
•
chan—0
•
inputMode—0
•
inputRange—0
•
polarity—0
•
driveAIS—0
Call SCXI_Track_Hold_Setup to configure the track-and-hold
circuitry of the SCXI-1520. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
inputMode—2
•
source—0
•
send—0
•
holdCount—1
•
DAQdeviceNumber—The value assigned by MAX
9
SCXI-1520 Calibration Procedure
6.
Call SCXI_MuxCtr_Setup to configure the DAQ device counter for
use as a multiplexer counter during SCXI channel scanning. Set the
following parameters:
•
deviceNumber—The DAQ device number assigned by MAX
•
enable—1
•
scanDiv—1
•
ctrValue—1
7.
Connect the calibrator to the appropriate analog input, starting with
channel 0. Refer to Table 1 to determine which pins on the 96-pin front
connector correspond to the positive and negative inputs of the
specified channel. For example, the positive input for channel 0 (S0+)
is pin C32. The negative input for channel 0 (S0–) is pin B32. If you
are using an SCXI-1314 terminal block, connect the calibrator to the
S0+ and S0– inputs on the SCXI-1314.
8.
Call SCXI_SCAN_Setup to set up the SCXI chassis to perform
a multiplexed scanning data acquisition. Set the following parameters:
9.
•
SCXIchassisID—The value assigned by MAX
•
numModules—1
•
moduleList—{1}
•
numChans—{1}
•
startChans—{The channel from step 7}
•
DAQdeviceNumber—The value assigned by MAX
•
modeFlag—0
Call SCXI_Configure_Filter to configure the filter on the module.
Set the following parameters:
•
chassisID—The value assigned by MAX
•
moduleSlot—1
•
channel—The channel from step 7
•
filterMode—0
•
freq—0
•
cutoffDivDown—0
•
outClkDivDown—0
SCXI_Configure_Filter returns the actual cutoff frequency that
the module uses as a 64-bit floating-point number, actualFreq.
SCXI-1520 Calibration Procedure
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10. Call SCXI_Set_Potentiometer to set the fine potentiometer to the
center position. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
channel—The channel number from step 7
•
value—2048
•
pottype—1
11. Call SCXI_Set_Potentiometer to set the coarse potentiometer
to the center position. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
channel—The channel number from step 7
•
value—62
•
pottype—0
12. Call SCXI_Set_Excitation to set the excitation voltage to zero.
Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
moduleChan—The channel number from step 7
•
excitationType—2
•
excitationValue—0
SCXI_Set_Excitation returns a 32-bit floating-point number
called actualExcitationValuePtr.
13. Call SCXI_Configure_Connection to configure the channel for
a full-bridge connection. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
moduleChan—The channel number from step 7
•
connectionType—6
14. Call SCXI_Set_Gain to set the gain you want to test on the module.
Set the following parameters:
© National Instruments Corporation
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
channel—The channel number from step 7
•
gain—The gain value you want to test. Refer to Table 2 for gain
values and test points.
11
SCXI-1520 Calibration Procedure
15. Set the calibrator to output the test point voltage from Table 2.
16. Call SCAN_Op to acquire the data. Set the following parameters:
•
deviceNumber—The device number of the DAQ device
•
numChans—{1}
•
chans—{0}
•
gains—1
•
buffer—[5000]
•
count—5000
•
sampleRate—10000
•
scanRate—5000
17. Call DAQ_VScale to scale the data returned by SCAN_Op. Set the
following parameters:
•
deviceNumber—The value assigned to the DAQ device by MAX
•
chan—0
•
gain—1
•
gainAdjust—1
•
offset—0
•
count—5000
•
binArray—The array returned by SCAN_Op
The result is voltArray, a set of scaled voltages measured with respect
to the output of the SCXI module.
18. Average the results returned by DAQ_VScale.
19. Record the averaged voltage from step 18 as Vmp and the calibrator
voltage as Vinp.
20. Set the calibrator to the negative test-point value for the same gain.
21. Repeat steps 16 through 18.
22. Record the averaged voltage from step 18 as Vmn and the calibrator
voltage as Vinn. You now have two pairs of data points, (Vmp, Vinp) and
(Vmn, Vinn), to use in the Gain Calibration Constants section.
23. Repeat steps 14 through 22 for the remaining gains you want to adjust
on this module.
24. Repeat steps 7 through 23 for the remaining channels you want to
adjust on this module.
SCXI-1520 Calibration Procedure
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Adjusting Calibration Constants
Complete the following steps to adjust the calibration constants on the
SCXI-1520.
Gain Calibration Constants
1.
Calculate the gain adjustment for each channel using the following
equation:
V mp – V mn
GainAdjust = ----------------------------------------------( V inp – V inn ) × gain
where
GainAdjust is a value used later in this process
Vmp is the measured output of the module given a positive input
voltage Vinp
Vmn is the measured output of the module given a negative input
voltage Vinn
gain is the gain setting of the module
2.
3.
© National Instruments Corporation
Call SCXI_Adv_Module_Write to write the new gain calibration
constants to the module. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
moduleClass—2
•
address—2 × iquo + 9, where iquo is the integer part of the
module channel divided by 2
•
numBytes—4
•
data—The value of GainAdjust represented as 4 bytes in
a 4-element array stored little-endian
•
whichAccess—0
•
regMethod— –1
•
subAddress—(296 × irem + 722) + (4 × index), where irem is the
integer remainder of the module channel divided by 2 and index
is the index from Table 2 that corresponds to the gain you are
adjusting
Repeat steps 1 and 2 for the remaining gains and channels.
13
SCXI-1520 Calibration Procedure
Offset Calibration Constants
1.
2.
Call SCXI_Calibrate and set the following parameters:
•
SCXIChassisID—The value assigned by MAX
•
moduleSlot—1
•
moduleChan—The number of the channel you want to calibrate
•
opCode—0
•
calibrationArea—0
•
SCXIgain—1
•
refVoltage—1
•
DAQdevice—The value assigned by MAX
•
DAQchan—0
Repeat step 1 for each of the remaining channels.
Excitation Calibration Constants
Note
This adjustment is not needed for the 0.0 V excitation.
1.
2.
Call SCXI_Adv_Module_Read to get the value of the 2.5 V reference
voltage on the SCXI-1520. Use the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
slot—1
•
moduleClass—2
•
address—3
•
numBytes—4
•
data—The array that returns the value of the SCXI-1520 2.5 V
reference voltage. The data is returned as 4 bytes in a 4-element
array stored little-endian.
•
whichAccess—0
•
regMethod— –1
•
subAddress—104
Calculate the excitation calibration constant to be written to the
module. Use the following equation:
ExcitationAdjust = Vexm/Vref_2.5
where
Vexm is the measured value of the excitation voltage from step 5
of the Verifying Voltage Excitation section
Vref_2.5 is the value of the 2.5 V reference voltage from step 1
SCXI-1520 Calibration Procedure
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3.
4.
Call SCXI_Adv_Module_Write to write the new excitation adjust
calibration constants to the module. Set the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
moduleSlot—1
•
moduleClass—2
•
address—2 × iquo + 9, where iquo is the integer part of the
module channel divided by 2
•
numBytes—4
•
data—The value of ExcitationAdjust represented as 4 bytes in
a 4-element array stored little-endian
•
whichAccess—0
•
regMethod— –1
•
subAddress—(296 × irem + 654) + (4 × index), where irem is the
integer remainder of the module channel divided by 2, and index
is the index from Table 3 that corresponds to the excitation voltage
you are adjusting
Repeat steps 2 and 3 for the remaining excitation voltages and
channels.
Reading New Calibration Constants to Memory
You can call SCXI_Get_Chassis_Info and SCXI_Get_Module_Info to find
variables (parameters) for SCXI_Set_Config. Refer to the Traditional NI-DAQ Help for
detailed function help.
Note
Reset NI-DAQ to read new calibration constants by calling
SCXI_Set_Config with the following parameters:
•
SCXIchassisID—The value assigned by MAX
•
chassisType—0 for SCXI-1000, 1 for SCXI-1001, 4 for PXI-1010,
5 for PXI-1011
•
address—0–31 as found in MAX
•
commMode—1
•
commPath—MIO device number
•
numSlots—physical number of slots in chassis, 4, 8, or 12
•
moduleTypes—array of length numSlots, with each element
corresponding to a slot in the chassis. Use –1 if the index corresponds
to an empty slot. Use 51 if the index corresponds to a slot containing
an SCXI-1520.
© National Instruments Corporation
15
SCXI-1520 Calibration Procedure
•
opModes—array of length numSlots, use –1 for an empty slot,
0 for multiplex mode, 1 for parallel mode, and 2 for parallel mode
using the secondary connector of the DAQ device
•
DAQboards—array of size numSlots, with 0 for all slots with no DAQ
device cabled to the module, and the MIO device number for the slot
containing the module cabled to the DAQ device
Verifying Adjusted Values
After completing the adjustments to the SCXI-1520, it is important that
you verify the analog input operation by repeating the steps listed in the
Verifying Gain and Offset Errors and Verifying Voltage Excitation
sections. Reverifying after adjustments ensures that the SCXI-1520 is
operating within its specifications.
Front Signal Connector Pin Assignments
The pin assignments for the SCXI-1520 front signal connector are shown
in Table 1. The front signal connector is a special 96-pin DIN C male
connector through which you make all signal connections. The terminal
assignments are as follows:
•
SX+ and SX– are for analog input
•
RSX+ and RSX– are for remote sense
•
PX+ and PX– are for excitation output
•
SCAX are for shunt calibration circuit A
•
SCBX are for shunt calibration circuit B
where X is the channel number.
The negative terminals are listed in Column B and the positive terminals are
listed in Column C. The pins labeled RSVD are reserved. Do not make any
connections to these pins.
SCXI-1520 Calibration Procedure
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Table 1. Front Signal Pin Assignments
Front Connector Diagram
Pin Number
Column A
32
SCB0
S0–
S0+
31
SCB0
RS0–
RS0+
30
SCB1
P0–
P0+
32
29
SCB1
SCA0
SCA0
31
28
RSVD
S1–
S1+
30
27
RSVD
RS1–
RS1+
26
RSVD
P1–
P1+
25
RSVD
SCA1
SCA1
24
SCB2
S2–
S2+
25
23
SCB2
RS2–
RS2+
24
22
SCB3
P2–
P2+
23
21
SCB3
SCA2
SCA2
22
20
RSVD
S3–
S3+
19
RSVD
RS3–
RS3+
18
RSVD
P3–
P3+
17
RSVD
SCA3
SCA3
17
16
SCB4
S4–
S4+
16
15
SCB4
RS4–
RS4+
15
14
SCB5
P4–
P4+
14
13
SCB5
SCA4
SCA4
12
RSVD
S5–
S5+
11
RSVD
RS5–
RS5+
10
10
RSVD
P5–
P5+
9
9
RSVD
SCA5
SCA5
8
8
SCB6
S6–
S6+
7
7
SCB6
RS6–
RS6+
6
6
SCB7
P6–
P6+
5
SCB7
SCA6
SCA6
4
RSVD
S7–
S7+
2
3
RSVD
RS7–
RS7+
1
2
RSVD
P7–
P7+
1
RSVD
SCA7
SCA7
A
Column
B
C
29
28
27
26
21
20
19
18
13
12
11
5
Column B
Column C
4
3
© National Instruments Corporation
17
SCXI-1520 Calibration Procedure
Specification Tables
Table 2 contains the specifications you should use when verifying and
calibrating the gain and offset of the SCXI-1520. If the module has been
calibrated within the last year, the test point value should fall between the
Lower Limit (V) and Upper Limit (V) values.
Table 2. SCXI-1520 Gain and Offset Calibration Table
Test Point (V)
Gain
Lower Limit (V)
Upper Limit (V)
Index
4.900000
1
4.891100
4.908900
0
0.000000
1
–0.004000
0.004000
0
–4.900000
1
–4.908900
–4.891100
0
4.260870
1.15
4.253130
4.268609
1
0.000000
1.15
–0.003478
0.003478
1
–4.260870
1.15
–4.268609
–4.253130
1
3.769230
1.3
3.762385
3.776077
2
0.000000
1.3
–0.003077
0.003077
2
–3.769230
1.3
–3.776077
–3.762385
2
3.266670
1.5
3.260733
3.272600
3
0.000000
1.5
–0.002667
0.002667
3
–3.266670
1.5
–3.272600
–3.260733
3
2.722220
1.8
2.717278
2.727167
4
0.000000
1.8
–0.002222
0.002222
4
–2.722220
1.8
–2.727167
–2.717278
4
2.450000
2
2.445550
2.454450
5
0.000000
2
–0.002000
0.002000
5
–2.450000
2
–2.454450
–2.445550
5
2.227270
2.2
2.223227
2.231318
6
0.000000
2.2
–0.001818
0.001818
6
–2.227270
2.2
–2.231318
–2.223227
6
2.041670
2.4
2.037958
2.045375
7
0.000000
2.4
–0.001667
0.001667
7
SCXI-1520 Calibration Procedure
18
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Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued)
Test Point (V)
Gain
Lower Limit (V)
Upper Limit (V)
Index
–2.041670
2.4
–2.045375
–2.037958
7
1.814810
2.7
1.811519
1.818111
8
0.000000
2.7
–0.001481
0.001481
8
–1.814810
2.7
–1.818111
–1.811519
8
1.580650
3.1
1.577774
1.583516
9
0.000000
3.1
–0.001290
0.001290
9
–1.580650
3.1
–1.583516
–1.577774
9
1.361110
3.6
1.358639
1.363583
10
0.000000
3.6
–0.001111
0.001111
10
–1.361110
3.6
–1.363583
–1.358639
10
1.166670
4.2
1.164548
1.168786
11
0.000000
4.2
–0.000952
0.000952
11
–1.166670
4.2
–1.168786
–1.164548
11
0.875000
5.6
0.873411
0.876589
12
0.000000
5.6
–0.000714
0.000714
12
–0.875000
5.6
–0.876589
–0.873411
12
0.753850
6.5
0.752477
0.755215
13
0.000000
6.5
–0.000615
0.000615
13
–0.753850
6.5
–0.755215
–0.752477
13
0.653330
7.5
0.652147
0.654520
14
0.000000
7.5
–0.000533
0.000533
14
–0.653330
7.5
–0.654520
–0.652147
14
0.563220
8.7
0.562195
0.564241
15
0.000000
8.7
–0.000460
0.000460
15
–0.563220
8.7
–0.564241
–0.562195
15
0.490000
10
0.489110
0.490890
16
0.000000
10
–0.000400
0.000400
16
© National Instruments Corporation
19
SCXI-1520 Calibration Procedure
Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued)
Test Point (V)
Gain
Lower Limit (V)
Upper Limit (V)
Index
–0.490060
10
–0.490890
–0.489110
16
0.426090
11.5
0.425313
0.426861
17
0.000000
11.5
–0.000348
0.000348
17
–0.426090
11.5
–0.426861
–0.425313
17
0.376920
13
0.376238
0.377608
18
0.000000
13
–0.000308
0.000308
18
–0.376920
13
–0.377608
–0.376238
18
0.326670
15
0.326073
0.327260
19
0.000000
15
–0.000267
0.000267
19
–0.326670
15
–0.327260
–0.326073
19
0.272220
18
0.271728
0.272717
20
0.000000
18
–0.000222
0.000222
20
–0.272220
18
–0.272717
–0.271728
20
0.245000
20
0.244555
0.245445
21
0.000000
20
–0.000200
0.000200
21
–0.245000
20
–0.245445
–0.244555
21
0.222730
22
0.222323
0.223132
22
0.000000
22
–0.000182
0.000182
22
–0.222730
22
–0.223132
–0.222323
22
0.204170
24
0.203796
0.204538
23
0.000000
24
–0.000167
0.000167
23
–0.204170
24
–0.204538
–0.203796
23
0.181480
27
0.181152
0.181811
24
0.000000
27
–0.000148
0.000148
24
–0.181480
27
–0.181811
–0.181152
24
0.158060
31
0.157777
0.158352
25
0.000000
31
–0.000129
0.000129
25
SCXI-1520 Calibration Procedure
20
ni.com
Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued)
Test Point (V)
Gain
Lower Limit (V)
Upper Limit (V)
Index
–0.158060
31
–0.158352
–0.157777
25
0.136110
36
0.135864
0.136358
26
0.000000
36
–0.000111
0.000111
26
–0.136110
36
–0.136358
–0.135864
26
0.116670
42
0.116455
0.116879
27
0.000000
42
–0.000095
0.000095
27
–0.116670
42
–0.116879
–0.116455
27
0.087500
56
0.087341
0.087659
28
0.000000
56
–0.000071
0.000071
28
–0.087500
56
–0.087659
–0.087341
28
0.075380
65
0.075248
0.075521
29
0.000000
65
–0.000062
0.000062
29
–0.075380
65
–0.075522
–0.075248
29
0.065330
75
0.065215
0.065452
30
0.000000
75
–0.000053
0.000053
30
–0.065330
75
–0.065452
–0.065215
30
0.056320
87
0.056220
0.056424
31
0.000000
87
–0.000046
0.000046
31
–0.056320
87
–0.056424
–0.056220
31
0.049000
100
0.048891
0.049109
32
0.000000
100
–0.000060
0.000060
32
–0.049000
100
–0.049109
–0.048891
32
0.042610
115
0.042507
0.042710
33
0.000000
115
–0.000059
0.000059
33
–0.042610
115
–0.042710
–0.042507
33
0.037690
130
0.037597
0.037788
34
0.000000
130
–0.000058
0.000058
34
© National Instruments Corporation
21
SCXI-1520 Calibration Procedure
Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued)
Test Point (V)
Gain
Lower Limit (V)
Upper Limit (V)
Index
–0.037690
130
–0.037788
–0.037597
34
0.032670
150
0.032577
0.032756
35
0.000000
150
–0.000057
0.000057
35
–0.032670
150
–0.032756
–0.032577
35
0.027220
180
0.027139
0.027305
36
0.000000
180
–0.000056
0.000056
36
–0.027220
180
–0.027305
–0.027139
36
0.024500
200
0.024421
0.024580
37
0.000000
200
–0.000055
0.000055
37
–0.024500
200
–0.024580
–0.024421
37
0.022270
220
0.022196
0.022350
38
0.000000
220
–0.000055
0.000055
38
–0.022270
220
–0.022350
–0.022196
38
0.020420
240
0.020342
0.020491
39
0.000000
240
–0.000054
0.000054
39
–0.020420
240
–0.020491
–0.020342
39
0.018150
270
0.018076
0.018220
40
0.000000
270
–0.000054
0.000054
40
–0.018150
270
–0.018220
–0.018076
40
0.015810
310
0.015737
0.015875
41
0.000000
310
–0.000053
0.000053
41
–0.015810
310
–0.015875
–0.015737
41
0.013610
360
0.013545
0.013678
42
0.000000
360
–0.000053
0.000053
42
–0.013610
360
–0.013678
–0.013545
42
0.011670
420
0.011603
0.011731
43
0.000000
420
–0.000052
0.000052
43
SCXI-1520 Calibration Procedure
22
ni.com
Table 2. SCXI-1520 Gain and Offset Calibration Table (Continued)
Test Point (V)
Gain
Lower Limit (V)
Upper Limit (V)
Index
–0.011670
420
–0.011731
–0.011603
43
0.008750
560
0.008689
0.008811
44
0.000000
560
–0.000052
0.000052
44
–0.008750
560
–0.008811
–0.008689
44
0.007540
650
0.007479
0.007598
45
0.000000
650
–0.000052
0.000052
45
–0.007540
650
–0.007598
–0.007479
45
0.006530
750
0.006475
0.006592
46
0.000000
750
–0.000052
0.000052
46
–0.006530
750
–0.006592
–0.006475
46
0.005630
870
0.005575
0.005690
47
0.000000
870
–0.000052
0.000052
47
–0.005630
870
–0.005690
–0.005575
47
0.004900
1000
0.004843
0.004957
48
0.000000
1000
–0.000052
0.000052
48
–0.004900
1000
–0.004957
–0.004843
48
© National Instruments Corporation
23
SCXI-1520 Calibration Procedure
Table 3. Excitation Limits
Excitation (V)
Lower Limit (V)
Upper Limit (V)
Index
0
–0.020000
0.020000
0
0.625
0.603125
0.646875
1
1.25
1.226250
1.273750
2
1.875
1.849375
1.900625
3
2.5
2.472500
2.527500
4
3.125
3.095625
3.154375
5
3.75
3.718750
3.781250
6
4.375
4.341875
4.408125
7
5
4.965000
5.035000
8
5.625
5.588125
5.661875
9
6.25
6.211250
6.288750
10
6.875
6.834375
6.915625
11
7.5
7.457500
7.542500
12
8.125
8.080625
8.169375
13
8.75
8.703750
8.796250
14
9.375
9.326875
9.423125
15
10
9.950000
10.050000
16
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