ADS1247: about error calculation

IronChef Han

Part Number: ADS1247

Tool/software:

Hi Support Team,

In page 17 of the document "3-Wire RTD Measurement System Reference Design, -200°C to 850°C",

I have one question on this page. In the equation (40), why the voltage drop(390.48mV) across RTD is used instead of one across the Rref?

Another question is how to analyze errors when the resistance on leads are not equal.

thanks

11 months ago

+1 Bryan Lizon86 11 months ago

TI__Guru 58751 points

Hi IronChef Han,

A gain error is relative to the input signal. So if the input signal is 1V and the gain error is 1%, then the error in volts is 1V * 0.01 = 10mV. If the input signal is then 100mV, then the error in volts is 100mV * 0.01 = 1mV. So even though the gain error is the due to RREF, it still affects the input signal, and is relative to the magnitude of the input signal (if you are looking at the error in volts)

You can refer to the information in this video to help resolve your second question about non-equal lead resistance in 3-wire RTD measurement systems: https://www.ti.com/video/series/precision-labs/ti-precision-labs-analog-to-digital-converters-adcs.html?videoId=6330517029112

-Bryan

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ADS1247: about error calculation