Texas Instruments XTR108 User Manual Download Page 38

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Software Overview

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SBOU123A – March 2012 – Revised September 2016

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XTR108EVM-USB Evaluation Board and Software Tutorial

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.