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Precision Data Converters
Precision Data Converters Forum
ADS1232 Offset Problem
Hi, I'm ussing the ADS1232 for a weight scale system, when the system start works fine but after of 3 or more minutes i have an offset in the data, for example when the weight system start i read and convert in weight 0.00 kg whit some noise of 0.01 but after of some time i'm reading 0.10 kg, and if i disconect the circuit and conect again i have 0.00 kg.
It sounds like you have some sort of charge related issue that is floating within part of your system. Make sure that you have a very good ground connection between the load cell and the ADS1232 device.
Thanks for your help, i changed the load cell and the adc is working fine now, i'm going to do some test in the system and if i have a problem i will post it.
Jesus Diamel Sarmiento
I have the same problem on the ADS1232REF eval board, after 1hr my 20KN load cell indicates -0.3Kg (seams not go further) instead of 0 when calibrated.
I did the internal calibration process many times, i restarted the board, nothing changes.
It apears that shorting the inputs didn't show the problem...
Do you have an idea to solve this ?
Can you diagram how you have your load cell connected to the ADS1232REF? Have you removed the jumpers J7 and J8? Those jumpers must be removed when a load cell is connected.
I connected my 20KN load cell to the 5Va,IN1+,IN1-,GND on the screw connector J5. Switch to 5Va.
The jumpers are removed, yes. I have checked every connection.
Bom rev D and PCA rev C, firmware 1.1.0d
It is possible for the load cell to change it's initial state (or return position) The software calibrates using a two point calibration. The first position is a no load weight and the second position is known calibrated weight. Once the system is calibrated, it may drift or return to some other value than 0 at the no weight condition. You should be able to press the TARE button which will reset the scale output to 0. After TARE, placing the calibrated weight back on the scale should give you the correct results (assuming you have already properly calibrated your system.)
Another issue can be noise or an unsettled digital filter. If the readings are not stable when calibrating, the result may not be fully representative of the actual input. The ADS1232 needs about 4-5 good conversion periods for the digital filter to be settled after an input step change.
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