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CN0287 accuracy analysis

Question asked by Suresha on Dec 9, 2013
Latest reply on Dec 17, 2013 by Suresha

Hi,

 

One of our new designs, requires us to implement RTD & Thermocouple measurement circuit.

We need to get a accuracy of better than "0.2% of FSR" over the operating temperature range of "-20°C to 60°C".

We have looked at CN0287 board & planning to use the same circuit in our board if the required accuracy is met.

 

The CN0287 specification says that accuracy of 0.5°C. Is this accuracy guaranteed over a specific temperature range?

 

For our accuracy analysis , we have identified the error introducing components as below :

 

RTD measurement :

 

  • Resistor Rref  - Tolerance & Temperature coefficient
  • ADC AD7193 - ENOB , INL , Offset error, Gain error , Offset drift , Gain drift

Due to ratio-metric cancellation,  change in excitation current & ADC reference voltage cancel out each other. Thermo-couple measurement :

  • ADC AD7193 - ENOB , INL , Offset error, Gain error , Offset drift , Gain drift
  • ADC Reference ADR3425 - Initial Accuracy, Line regulation , Load regulation, Output Noise
  • Cool Junction Compensation ADT7310 - Accuracy ( 0.5°C )

 

Please let us know if we have missed out any parameter in our analysis.

 

Also, it will be helpful if you can share any document related to accuracy analysis done on CN0287.

 

Looking forward to your response.

 

Regards,

Suresha N S

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