--Previous Message-- : Hi Bert : : I am working on a new VTTC project and I have to measure the grid current : (don't want to go over the ratings of the tube, even I dont know very well : what is the maximum permited). The tube is a GU5B russian stuff. : : I made a little drawing: what is the correct way to introduce the DC : A-meter in the circuit to get the right reading? A, B, or C variant? : : http://www.geocities.com/gemaria_ro/gu5btrA.html : : Thanx a lot : : teslina : > : > :
All three approaches will work. However, I would recommend configurations "A" or "B" since these allow the meter to operates at near ground potential. I would, however, recommend adding a small bypass capacitor across the meter to bypass its coil inductance. Configuration C may subject the meter to high voltage stress, especially if the meter uses metal case. This can represent a shock hazard (of the case is not grounded) and may coil-case flashover if the case is grounded (for safety).