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| HX711-based milliohm meter |
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| Kalvin:
What happens if you heat only the bridge components instead of the ADC? Does it make the results drift? If the ADC has a built-in temperature sensor, you could possibly measure ADC's temperature and apply precomputed temperature compensation coefficients for the measurement values, after which you should get pretty good results. Br, Kalvin |
| Kalvin:
Of course, you could provide a constant temperature to the ADC which would solve temperature related drifting problem. Similar technique is used in high precision, temperature stabilized oscillators TCXO. |
| dannyf:
That would be purely a test of the resistors' tempco. What troubles me is the negative correlation - which kills any ratiometric approach. |
| Kalvin:
Heating the ADC from room temperature to finger-burning temperature is quite a big change. As I recall, the original problem was the drifting in room temperature when a resistor was applied. That's why I was also interested in seeing the temperature effect on the bridge components and whether there might be any galvanic voltage sources which could explain the drifting. However, this galvanic voltage source is just my pure speculation, but as we are dealing with a high precision measurements, even small thermal/galvanic voltage sources may ruin the day. Br, Kalvin |
| dannyf:
There is no bridge to speak of: the set-up is ratiometric. As such, it requires positive correlation, preferred 100% correlation - aka the same tempco. Anyway, here is the iron applied to the resistors, starting at count 300 and off at count 400. I have to say that I cannot see a difference here, vs. the prior chart. |
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