I have a potentiometer that has a range of 0-70ohms. I have a resistance gauge that measures 0-140ohms. Is there any way I can dynamically double the potentiometer resistance? Thanks.

 

Use two in series?

 

Dynamically, you say? Look up "gyrator".

 

Is this for a fuel gauge mod?

 

Is this for a fuel gauge mod?

Yes. The fuel sending unit on the tractor has a range of 0-70ohms. I thought a reproduction gauge would be the same ohm range but it is 0-140ohms. I could replace the sending unit or find an original gauge that is the correct ohm range, but I was hoping there would be another solution.

 

Is this gauge connected directly from +12 to grounded rheostat?

Can you measure current at full and empty range of the gauge you will be using?

Or find more specs?

 

Here's one way you could effectively double the pot resistance.
The 70 Ohm pot plus components in the dotted rectangle of the right-hand circuit behave similarly to the 140 Ohm pot in the dotted rectangle of the left-hand circuit. The graphs show that the voltages at points p1 and p2 track each other as the pot resistances are varied from min to max.

 

Here's one way you could effectively double the pot resistance.
The 70 Ohm pot plus components in the dotted rectangle of the right-hand circuit behave similarly to the 140 Ohm pot in the dotted rectangle of the left-hand circuit. The graphs show that the voltages at points p1 and p2 track each other as the pot resistances are varied from min to max.

Thanks. Where do I hookup the gauge? I built the circuit in CircuitMaker but I can not get it to work correctly.

What simulation software do you use?

 

How about just reducing the voltage to 6 volts?

 

Where do I hookup the gauge?

R1b represents the gauge, so the gauge connects to the collector of Q1 (point p2).

What simulation software do you use?

LTspice (free download from Linear Technology).

I built the circuit in CircuitMaker but I can not get it to work correctly.

You don't have R1b going to 12V in your circuit.