On Thu, Oct 31, 2024 at 01:37 AM, Henry Spragens wrote:
Here’s how to find out for yourself, if you have a resistor of around 1M. Measure the DC voltage of a battery or circuit around 1 to 12 volts. Now attach the 1M resistor in series with the red voltmeter test lead and measure the voltage again. If the input resistance of the meter is 1M, it will cut the voltage measurement in half, half of the voltage being dropped across the added 1M resistor and half across the meter itself. If the meter is 10M, the reading on the meter will drop only 9%. Total series resistance being 11M, and the meter being 91% of the total. (90.909090...% for the nit picky.)
The resistor doesn’t have to be 1M, it can be any value above 330K or so, just enough to affect the reading differently for a 1M meter vs a 10M meter.
Hi Henry
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Many thanks for link and the detailed instructions!
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I bought the Mastech MAS830 in a real electronic shop about 35 years ago. The atmosphere in the shop was nice. Small boxes with countless parts everywhere. :-)
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For the measurements you suggested I used a battery holder with 4 AAA cells.?
Measured DC-Voltage: 6.47V
As a resistor I added eight 68K resistors (SimpleP48 stock) in series to a breadboard.
Measured resistance: 0.542M
Then I attached the 0.542M resistor in series with the red voltmeter test lead and measured the voltage of the battery holder again.
Measured DC-Voltage: 4.17V
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The meter dropped around 35.54%
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I still don't fully understand what this means for the voltage measurements of the NT1-a circuit. Do I need to add about 35% to each voltage measurement to get the correct voltage values?
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