Quote:
Not in series, in parallel from the sender to earth to 'pull' the output.
I did start typing loads of equations, 1/Rt=1/R1+1/R2 etc then got bored so here's a calculator!
http://www.sengpielaudio.com/calculator-paralresist.htm
Decide what your mid-point 'normal' temperature resistance should be and then choose a value to suit the sender.
Yes, I did understand you ment in parrallel:
The other way to write the equation is Rl = Rs*Rp/(Rs + Rp); where Rl is the load on the guage, Rs is the sensor, and Rp is the parallel shunt.
Exagerating the change in the resistance of the sensor to show the effect: At the hot end, the resistance of the sensor, Rs, is small compared with Rp. In which case (Rs + Rp) is nearly equal to Rp. Hence Rl is nearly equal to (Rs*Rp/Rp)), and Rl is nearly equal to Rs. In which case the shunt makes little difference to the guage reading.
But at the cold end when Rp is small compared to Rs, (Rs + Rp) is nearly equal to Rs, so Rl is nearly equal to Rp, and the sensor makes less difference to the guage.
And that means, at the cold end, changes in the sensor have less effect on the guage than without the shunt, but at the hot end, the shunt hardly makes a difference: so the guage is less sensitive at the cold end.
Yes, I exagerated the change in Rs, but it is more than 2 decades by the data given, so there will be a decernable effect.
Putting a series resistor in would only reduce the reading, though (I think) obviously it would reduce the hot end reading more than the cold end ones.
Graham