Was fixing my non working meter and came across a circuit on the Koos Nolst Trenite website. I built this circuit and have got it working, however the instructions on his site are not so clear. This lead me to a thread on this site with instructions on setting up and building. http://www.forum.exscn.net/threads/ralph-hilton-mk-4-meter-schematics.4109/page-2 I wanted to create a new thread to alert people that this circuit works and can be built and calibrated. As an aside the circuit looks very much like Ulric/s Biometrics meter from the early 90s. This is the meter I was fixing (it had a damaged meter movement). I could not download the circuit in the thread so I also have redrawn it and included it here.