Here is a nice winter project. No bridge here!
Suggestions: Find a well made, LARGE 1 mA meter with fine calibration ticks.
Caddock sells prefab precision resistor chains with tap points, Consider using them. Also, consider doubling or tripling the resistance of the chain, and using about 3 Meg in the probe. You might need to take the plate voltage up to 40 or 50 V if you do. Consider a VR tube or Zener for the plate.
Making a nice meter scale is a pain. Idea: Set zero and infinity points on phms, then record MANY calibration points using precision resistors or helipots of various values. Run a nonlinear regression, and get a computer print out of measured ohms for any given tick mark.
Build in a fancy case. Have a nice desk ornament.
http://www.americanradiohistory.com/Archive-Radio-News/40s/Radio-News-1949-08-R.pdfMatt
