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5.3.3 Step 3: First Corrections
Once the initial settings have been written to the XTR108 and the RTD Emulator has been configured,
output measurements can be taken at the minimum- and maximum-scale values.
Configure the DMM for dc current or dc voltage measurement, depending on which mode is being used.
Click the Set RTD Emulator to Minimum Scale button to route the minimum-scale output signal to the
DMM. Observe the output measured by the DMM and enter the result into the Enter Minimum Output
control.
Next, click the Set RTD Emulator to Maximum Scale button to route the maximum-scale output signal to
the DMM. Observe the output measured by the DMM and enter the result into the Enter Maximum Output
control.
Finally, click the Calculate First Corrections button to perform the first corrections based on these
measurements and write the updated configuration to the XTR108 and EEPROM.
NOTE: If the 34401A multimeter is connected to the PC by the NI GPIB-USB-HS controller, the
XTR108EVM-USB software automatically configures the 34401A for dc voltage or dc current
measurement, measures 10 samples of the output over a 5-second interval, and enters the
average output value into the Enter Minimum Output and Enter Maximum Output controls.
5.3.4 Step 4: Second Corrections
A second maximum-scale output measurement is required to complete calibration. Click the Set RTD
Emulator to Maximum Scale button to once again route the maximum-scale output signal to the DMM.
Observe the output measured by the DMM and enter the result into the Enter Maximum Output control.
Click the Calculate Second Corrections button to perform the second corrections based on this
measurement and write the updated configuration to the XTR108 and EEPROM.
5.3.5 Step 5: Error Calculator
The Error Calculator section allows the user to determine the error (expressed as a percentage of full-
scale) at minimum-scale, mid-scale, and maximum-scale output levels. Click the Set RTD Emulator to
Minimum Scale button to route the calibrated minimum-scale output signal to the DMM. Observe the
output measured by the DMM and enter the result into the adjacent Measured Output control. The Percent
Error indicator automatically updates with the calculated error value. Repeat this process for the mid-scale
and maximum-scale values.
5.3.6 Step 6: Underscale and Overscale Calibration
Once the normal output span of the XTR108 has been calibrated, the underscale and overscale output
can also be calibrated. The Desired Underscale and Desired Overscale indicators display the output levels
set by the loaded model file. Click the Calculate First US/OS Settings button to write the desired
underscale and overscale settings to the XTR108 and EEPROM.
Next, click the Set RTD Emulator to Underscale button to configure the RTD Emulator for underscale
output and route the underscale output signal to the DMM. Observe the output measured by the DMM and
enter the result into the Enter Measured Underscale control.
Next, click the Set RTD Emulator to Overscale button to configure the RTD Emulator for overscale
output and route the overscale output signal to the DMM. Observe the output measured by the DMM and
enter the result into the Enter Measured Underscale control.
Finally, click the Calculate US/OS Corrections button to perform the underscale and overscale
corrections based on these measurements and write the updated configuration to the XTR108 and
EEPROM. The calibrated values can be verified by clicking on the Set RTD Emulator to Underscale and
Set RTD Emulator to Overscale buttons after the calibration is complete.
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XTR108EVM-USB Evaluation Board and Software Tutorial SBOU123–March 2012
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