VTVM Question

[Joe Rossi]

Hello Friends, long time no see. I'm currently restoring/renovating a Heathkit V-7 VTVM, and I have a question: Why is the 1 Meg resister wired inside the DC probe? Would it be subverting Ohms Law ( ) to hard wire the resister in the box, and then use a new, updated probe? Any help and enlightenment would be very kindly appreciated! Thanx, Joe

[rghines1]

Think it was intended to isolate the capacitance of the coax cable, etc when making voltage measurements in RF circuits to reduce de-tuning them.

Another bad scenario is measuring a grid voltage on an oscillator stage expecting to see -5V or so but instead reading zero. The capacitance from the meter is attenuating feedback leading you to believe the oscillator is bad.

Richard

[Joe Rossi]

Thanks Richard!