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variation in readings due to changes in temperature

SUCHITRA BHIDE
Prodigy 230 points

Other Parts Discussed in Thread: MSP430F2013, OPA333

Hi

I am developing a digital weight scale using TI OPA333, MSP430F2013 and tps71533.  What I am seeing is the OPA333 doesn't give stable output with variation in temperature.

If I vary the temperature from 26 degrees to 60 degrees the output of the opamp is as follows

26 degrees - 264

35 degrees-  262

40 degrees - 258

45 degrees - 262

55 degrees - 264

The worst part is the reading is not the same when the temperature rises from 26 to 55. I mean I am getting different readings when the temperature rises from 26 to 55.

These readings are not the same as when the temperature falls from 55 to 26.

Any idea how to fix this problem

Thanks in advance

Kind regards

Suchitra

 

  • 0
    Guru 227245 points

    Without knowing the circuitry and how and what you measure, I cannot help you much.

    Just that you see a 2.4% change in output over a temperature change of 30°.
    A quick look into the regulator datasheet shows some output change in the regulator output which looks to have a peak somewhere where your readings are the lowest. So it could be related to supply voltage change. Also, the MSPs internal voltage reference drifts with temperature too. (I recommend using the TS431BCX shunt regulator as external reference, it has 2.495V+-0.5% and far less temperature drift)
    But without knowing the circuitry, it is just plain guessing.

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