Datasheet

Table Of Contents

Software Overview

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5.2.2 Step 2: Calculate Resistor Values

When the Calculate Resistors button is clicked, the XTR108EVM-USB software uses the operating

conditions entered in Step 1: Enter Operating Commands to calculate the best values for R

SET

, R

LIN

, R

and R

(for each enabled channel).

The R

SET

value is critical to proper XTR108 operation (see the I_REF DAC section). If the software cannot

find a suitable R

SET

value, an error message is displayed as shown in Figure 21. This error is typically

caused by narrow or conflicting temperature ranges on multiple channels. If you encounter this error,

widen your temperature ranges slightly and click the Calculate Resistors button again.

Figure 21. R

SET

Error

The XTR108EVM-USB software also performs a linearity check as part of the Calculate Resistors

functionality. If the software predicts that a post-calibrated error less than 0.1% of full-scale is not possible,

a warning message is displayed as shown in Figure 22. This error is typically caused by very wide

temperature ranges on multiple channels. If you encounter this warning, narrow your temperature ranges

slightly and click the Calculate Resistors button again.

Figure 22. Linearity Warning

5.2.3 Step 3: Install These Resistors

This area of the Find Resistors tab displays the calculated resistor values for R

SET

, R

LIN

, R

, and R

(for

each enabled channel). Install these resistors on the XTR108EVM-USB Sensor Board, either by soldering

surface-mount resistors or installing through-hole resistors in the pin sockets. The R

indicator for disabled

channels is grayed out.

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

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