Microchip logo
  • All
  • Products
  • Documents
  • Applications Notes

AN1154

Title:
Precision RTD Instrumentation for Temperature Sensing
Name:
AN1154
Date:
05/06/2013
Author:
Ezana Haile
Description:
Precision RTD (Resistive Temperature Detector) instrumentation is key for high performance thermal management applications. This application note shows how to use a high resolution Delta-Sigma Analog-to-Digital converter, and two resistors to measure RTD resistance ratiometrically. A ±0.1°C accuracy and ±0.01°C measurement resolution can be achieved across the RTD temperature range of -200°C to +800°C with a single point calibration. A high resolution Delta-Sigma ADC can serve well for high performance thermal management applications such as industrial or medical instrumentation. Traditionally, RTDs are biased with a constant current source. The voltage drop across the RTD is conditioned using an Instrumentation Amplifier which requires multiple resistors, capacitors and few operation amplifiers and/or a stand-alone instrumentation amplifier. This analog instrumentation technique requires a low noise and stable system to calibrate and accurately measure temperature. It also requires an operator for optimization on the production floor. With the Delta-Sigma ADC solution, the RTD is directly connected to the ADC (Microchip?s MCP3551 family of 22 bit Delta-Sigma ADCs) and a single low tolerance resistor is used to bias the RTD from the ADC reference voltage (Figure 1) and accurately measure temperature ratiometrically. A low drop out linear regulator (LDO) is used to provide a reference voltage.
Keywords:
Precision RTD, RTD Instrumentation, RTD Self-Heat, RTD Linearization, RTD Simulator, MCP3551, Ratiometric
 
Application Notes & Source Code
 Last Updated
Size
 
  AN1154
  05/06/2013
  274KB
Silicon Products