[R-390] Correcting for meter sensitivities?

[Richard Loken]

The question is not as easily answered as all that.  Your readings are affected
by how much your meter loads the circuit but how much your meter loads the 
circuit depends on the resistance of the meter and characteristics of the 
item under test.  A 1000 ohm/volt meter has no impact on the reading of a
fully charged 12V car battery but you will get big time lying if you try to
read the control grid voltage on your favourite IF stage.

That is not what you really want to know.  The load resistance of a VOM is
the rated reistance multiplied by the full scale voltage on the setting you 
are using so:

			
	DC Full Scale		1000 ohm/V	20,000 ohm/V
	-----------------------------------------------------
	10			10,000 ohm	200,000 ohm
	50			50,000 ohm	1,000,000 ohm

In your case, throw a resistor across the meter to load the circuit
appropriately.  If you use a DVM or a VTVM then you can ignore the meter
resistance and just calculate the resistance that a 1Kohm/volt meter would have
and put it in parallel with the probes.
---
   Richard Loken VE6BSV, Systems Programmer - VMS  
   Athabasca University
   Athabasca, Alberta Canada
   ** richardlo@admin.athabascau.ca **