Which is more stable

[kinarfi]

In the attached drawing, I used 5k resistors in the Wheatstone Bridge, If I change the resistors from 5 to 10k or even a 100K or higher, will it effect the stability of the circuit. The power is supplied by car battery, so supply loading shouldn't be a problem. As I said on the attachment, My guess is NO.
But it will make the 50 ohm pot more precise.
Is having a higher current flow more or less stable than a lower current flow for the same voltage, or is it the same?

Kinarfi

 

[MikeMl]

Some light reading.

I'm thinking you should be using fixed resistors (stable, 1% metal film) which are ~ the same value as the foil resistors.

 

[crutschow]

The amount of current flow really has little to do with stability. As Mike stated it's likely best to use stable fixed resistors approximately equal in value to the strain-gage resistors.

But that may not improve your temperature stability. If not, you might try using a heat gun at a low heat level to change the temperature of various parts of the circuit to see if you can determine specifically what is temperature sensitive.

 

[Boncuk]

I suggest to use 0.1% tolerance metal film resistors as they are used in DMMs. They have a very low temperature drift.

From 0.1% resistor tolerance you can expect not more than 0.1% input offset, which should be corrected within the amplifier circuit.

Boncuk

 

[kinarfi]

Thank You gentlemen, pretty much what I expected, current not so important, correct resistor choice is. Mike, that's not so lite.
Thanks Again,
Kinarfi

 

[kinarfi]

I have found an example of where more current is more stable than less current, on my present project, fuel gauge, I am finding that as I test the circuit by attaching my DSO-2150 usb scope to the circuit, it changes everything, the scope leads have a 1 Meg input resistance and 25pf to ground and my Fluke DVM has an 11 Meg input impedance. If the resistor used in a circuit, are in 10s of K ohms and only a few 100s of K ohms, my scope and meter will have very little effect. Mike's design works great on Spice and seems to be working, but I can't get it to work and can't figure out why because of the test equipment loading.
Kinarfi