[volt-nuts] 34401A Why 10M ohm default i/p resistance?
volt-nuts at adobe-labs.com
Thu Apr 10 17:52:13 EDT 2014
On 4/10/2014 3:18 PM, Tony wrote:
> Gordon wrote:
>> Pure conjecture: So that the reading on the 34401A matches that on a
>> $20 DVM.
> I assume you mean when the DVM is disconnected - otherwise you
> wouldn't spend more than $20 on a meter! But I said that in my
> original post:
Actually, I meant while connected. For example, you want to do a
quick-and-dirty check on a voltage. Say you had previously set the
voltage to a specific value using the 34401A . Sometime later you want
to check the voltage but the 34401A is not available. So, you use your
10 M-Ohm Fluke handheld DVM. If your source impedance is high and you
set the voltage with the 34401A set to 10 G-Ohm you would get a
significantly different reading with the Fluke. If the voltage was set
with 34401A in 10 M-Ohm mode, you should get the same reading (within
the accuracy of the Fluke).
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