| Electronics > Beginners |
| use low resistance wire as potentiometer in ADC |
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| topcat:
Hello, I am building a little application where I want to seance to position of a wiper on a long wire (approx 1m). It a copper wire so resistance is very low. Ideally I could just connect one end to GND and the other to VCC and directly input the moving seance arm into the ADC input. But obviously current flow will be too high in my wire. Is there any simple approach for this? Adding a current limiting resister changes the voltage gradient across my wire, and I really want to have good dynamic range maybe not the whole 10bits but close to 0-5v Thanks Dag. |
| timelessbeing:
Well if you're going to summon spirits from the realm of the dead, I think silver is the appropriate metal to channel energy. |
| tszaboo:
You could place the potentiometer in a bridge (with a series resitor), called wheatstone bridge, and then amplify the signal with an instrumentation amplifier. Or use an ADC with a PGA in it. Dont expect to solve this problem without adding components. |
| Brumby:
My first thought drifts towards Nichrome - but I don't know if that will be a suitable Medium. |
| Gyro:
Why does the wire need to be copper? It will have poor resistance to mechanical wear, which will degrade its linearity. Also Copper has a high temperature coefficient (it will get hot), so it won't be linear near where it is terminated (cooled) at the ends and probably at the wiper too if it has any thermal mass. |
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