Datasheet

Table Of Contents

Use these trim pots to

adjust RTD_Min value

Use these trim pots to

adjust RTD_Mid value

Use these trim pots to

adjust RTD_Max value

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Software Overview

5.3.1 Step 1: Initialize

Before calibration can take place, a model file must be loaded into the software. The XTR108EVM-USB

software automatically loads the most recent model file into memory at startup, but a different model file

can be selected by clicking the Load Model File button. The path of the loaded model file is shown in the

Model File indicator.

After loading a model file, use the channel-to-calibrate control to select which channel should be

calibrated. Disabled channels in the model file are grayed out and unable to be selected. After selecting a

channel to calibrate, click the Calculate Initial Settings button to write the initial configuration to the

XTR108 and EEPROM.

5.3.2 Step 2: Set RTD Emulator

The next step in the calibration procedure is to set the XTR108EVM-USB Interface Board RTD Emulator.

Once the Calculate Initial Settings button is pressed in Step 1: Initialize, the Set RTD_Min, Set

RTD_Mid, and Set RTD_Max buttons are enabled and the calculated resistance values for each channel

are displayed. As shown in Figure 25, the resistance value of each RTD Emulator channel can be set by

adjusting the trim pots of each channel with a small flat-head screwdriver.

Figure 25. Adjust RTD Emulator

Click the Set RTD_Min button to set the resistance of the RTD_Min channel. This button configures the

XTR108EVM-USB Interface Board to route the RTD_Min resistance to the DMM through the multimeter

connect terminals. Configure the DMM for four-wire resistance (Ω 4W) measurement, then adjust POT1

(coarse) and POT2 (fine) until the resistance measured by the DMM matches the value shown by the

RTD_Min indicator in the XTR108EVM-USB software.

Next, click the Set RTD_Mid button to set the resistance of the RTD_Mid channel. Adjust POT3 (coarse)

and POT4 (fine) until the resistance measured by the DMM matches the value shown by the RTD_Mid

indicator in the XTR108EVM-USB software.

Finally, click the Set RTD_Max button to set the resistance of the RTD_Max channel. Adjust POT5

(coarse) and POT6 (fine) until the resistance measured by the DMM matches the value shown by the

RTD_Max indicator in the XTR108EVM-USB software.

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 four-wire resistance

measurement.

SBOU123–March 2012 XTR108EVM-USB Evaluation Board and Software Tutorial

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