Good solution, Paul! Mentally dividing by ten is easy enough and you
retain all of the advantages of using the VTVM probe.
Dennis AE6C
Well....'sorta. The divide by ten works well and it's an easy mental
exercise. But in creating a 1 meg/100K divider, the load across the voltage
sampling point is reduced from 10 meg to 1 meg. That undermines the purpose
of the resistive probe except that the effects from cable capacitance and
lead inductance are swamped. But if the source Z providing grid voltage,
for example, is greater than 100K big errors will start setting in.
So...next I'm going to change the 1 meg resistor in VTVM probe to 10 meg
(like the 100x probe), and then try a variable shunt at the DMM end to find
the value where 10:1 is achieved. That 10 meg is a high value for low
voltage readings and I'm not sure how stable readings will be. I think 10
meg is commonly available in carbon film, but tougher to find in metal film.
Paul, W9AC
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