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Do I have a problem when ADC0OVR in ADCSTA is activated on a ADuC7060

Question asked by tfrauenrath on May 9, 2012
Latest reply on May 25, 2012 by tfrauenrath

In my actual design I switch between several RTD`s connected with three wires. I use both current sources and reference via 5k6 resistor for IEX0. It is connected like this:

 

IEX0 & Ref+---------[5k6]----------- Ref-  & Analog in0 ------------------> RTD+

IEX1 & Analog in 1 ---------------------------------------------------------------> RTD-

Ground -------------------------------------------------------------------------------> RTD GND

 

 

RTD- and RTD GND are connected with each other at the RTD. Because of simplicity the C-mos switched ADG713 are not mentioned here.

 

I use excitation current of 200µA for each source. By doing this I cancel the influence of the cable resistance.

 

 

The circuit and my source code is doing fine, but the ADC0OVR is alway set as soon as I connect my RTD. Does that mean my measurement is unstable?   Are there any code examples for 3 wire RTD applications?

 

 

Thank you!

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