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ADUCM360 converter noise is high, possible trouble with PGA

Question asked by iSeaSolutions on Sep 3, 2014
Latest reply on Sep 5, 2014 by iSeaSolutions

I have both the CN0221 and ADUCM360 Eval kit.   Running the examples, I'm not seeing stability on the temperature sensor.    I have placed both the boards in a box to limit thermal changes and what I see is drift and noise.   

 

At one point I stumbled across another user who was experiencing problems and the recommendation was to ground AIN0 on the ADUCM360 eval kit.   I've tried various changes to the software, particularly RTD_Demo, but am unable to get stable results.

 

If there are software updates internal to ADI, please let me know as I've downloaded the latest software from an FTP site but it provides the same poor quality (10 bit ENOB at best) results for the RTD_Demo.

 

Assuming the RTD circuit design may not be capable of more than 10bits, I connected a 10K potentiometer between AVDD and AGND with wiper on AIN2 and adjusted it for mid range.    I then configured the software to use ADC0, following what was done to setup ADC1.

 

I've got interrupts, sample buffer, setup, but am likely facing some sort of setup problem as I'm reading the same result each time (24bit stability, but not at all related to the signal).

 

I'm very likely making a mistake in the code especially since I followed the software for the noisy RTD code.

 

I'm working on a high resolution pH sensor and it would be great to know if the ADUCM360 is capable of more than 10 bits real world resolution.   I'd like to run software to evaluate the ADUCM360 performance, ideally with a potentiometer hooked up to AIN2.  

 

I will post my code, however the 'attach' link does not seem to be working for this initial post.

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