Tool/software:
Dear Sir/Madam,
We have used the device ADS1231 in our new design "PLC - Load Cell Input module". This module provides one input channel to interface with a 4-wire or 6-wire strain gauge load cell sensor, supporting sensitivity levels from 0 to 3 mV/V.
Currently, our design is in the final testing phase of R&D prototyping. During this phase, we have observed an issue: at room temperature (25C) the module output takes 30 to 60 minutes to stabilize, and the measured output count drifts from its initial value over this period.
For example, we used a load cell calibrator to apply a 3 mV/V input to the module. For 3mV input applied, the expected digital output count for this input is 32,000. However, we observed that the count initially starts at approximately 32,001 and slowly increases, stabilizing at around 32,011 after 30 minutes. Please refer to the table below for detailed observations.
| Time (Minutes) | Time (hh:mm) | Analog input: 3 mV/V | |
| Min Count | Max Count | ||
| 0 | 10.30 | 32001 | 32005 |
| 5 | 10.35 | 32003 | 32008 |
| 10 | 10.40 | 32004 | 32009 |
| 15 | 10.45 | 32005 | 32010 |
| 20 | 10.50 | 32006 | 32010 |
| 25 | 10.55 | 32007 | 32011 |
| 30 | 11.00 | 32006 | 32011 |
| 35 | 11.05 | 32007 | 32010 |
| 40 | 11.10 | 32007 | 32010 |
| 45 | 11.15 | 32007 | 32011 |
| 50 | 11.20 | 32007 | 32010 |
| 55 | 11.25 | 32007 | 32011 |
| 60 | 11.30 | 32007 | 32010 |
We would appreciate your guidance on the possible cause of this behavior. Specifically:
-
What might be causing the output to take 30 minutes or more to stabilize?
-
What could be contributing to the gradual increase in count values despite a constant input?
For your reference, we have attached the schematic diagrams for the ADS1231 circuit and the input channel.
We kindly request your feedback and support in resolving this issue.
Best Regards
Rohidas Sawant
R&D Dept.
