[R-390] Hickok Tube Tester Calibration

[Barry]

Apparently, ohms/volt applies to the full-scale reading for a given range.   For a 1000 ohms/volt meter with a 0 to 100 volt range, the meter presents 1000 * 100 ohms (100k ohms) when the meter is reading full scale.  I was trying to interpolate the ohms that's presented to the circuit from the meter for, say, 10 volts, 20 volts, 50 volts, 75 volts, etc. by multiplying the voltage reading by the ohms/volt specification which isn't correct.

Unfortunately, I think the only thing I enlightened was my stupidity regarding the subject.  I should know better.

Thanks,
Barry - N4BUQ

> Enlighten us all.
> 
> On Mon, Jan 6, 2025 at 12:06 PM Barry Scott <72volkswagon at gmail.com> wrote:
> 
>> A list member set me straight on this.  I was approaching it a bit
>> incorrectly but understand it now.
>>
>> Thanks,
>> Barry - N4BUQ
>>
>> On Mon, Jan 6, 2025 at 11:51 AM Barry Scott <72volkswagon at gmail.com>
>> wrote:
>> >
>> > I'm in the process of refurbishing my Hickok 752A and I have a general
>> > question regarding the calibration procedures.
>> >
>> > All voltage measurements are supposed to be taken with a 1000 ohm/volt
>> > meter and I don't have a meter like that.
>> >
>> > From what I understand, if one measures, for example, 150VDC with a
>> > 1000 ohm/volt meter, then the meter is placing a 1,000 ohms/volt x 150
>> > volts = 150,000 ohms load to the circuit being measured.  Using a
>> > 20,000 ohms/volt meter would only present a 3 megohm load for 150
>> > volts which is significantly different and result in a higher reading
>> > for that same 150 volts.
>> >
>> > Is there a way to "mimic" a 1,000 ohms/volt meter with a meter with a
>> > much higher sensitivity?  The closest meters I have are 20,000
>> > ohms/volt so looking for some suggestions.
>> >
>> > Thanks,
>> > Barry - N4BUQ
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> 
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> Moe Fretz
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