Multimeter 101

[Buk]

In the circuit I'm trying to reverse engineer I wanted to test change in the (static) resistance seen between ground and the mic input when the button is pressed.

When pressed, it measures as 0.7Ω -- which is the resistance of a ferrit bead inline with the mic input.

When closed, it measures ∞ on diode/bell, 20Ω & 2000Ω settings; but on the 20kΩ setting it measure 1.80 (sometimes 1.79 or 1.81 probably dependant on how good a contact I'm getting).

This confuses me. I should be seeing 1800(ish) when the range is set to 2000Ω?

What does this mean? Is my meter crap, or is there some other explanation?

 

[sagor1]

Some lower end multimeters use different voltages on different resistance ranges. At lower voltages, it may not be enought to pass through a diode junction (hence infinity/open), At other resistance ranges, the voltage may be higher and manages to get over the diode junction and produce some readings.

 

[Pommie]

How are you powering it?

Mike.

 

[Buk]

How are you powering it?

The circuit? I'm not.

The MM uses a pp9.

 

[JimB]

Some lower end multimeters use different voltages on different resistance ranges.

If this is a digital multimeter that you are using, the meter will be trying to drive a a constant current through the "resistance" which it is trying to measure.
The voltage across the resistance will depend on the current and the value of the resistance.

If you have a different meter, you may get better results using that one.

It could be that the circuit that you are trying to measure is not amenable to measurement by a simple multimeter.

JimB