I'm curious about the behavior of common digital multimeters. I understand the concept of meter loading on a circuit, but I never noticed before now. my multimeter seems to be creating a current path between the cathode and anode of my circuit when it is reading voltage. Enough current that it will visibly dim an led when measuring the voltage drop across the diode. it will also even cause enough current to light up an led. I noticed this when I removed a wire connecting the cathode of the led I was examining to my surprise it stayed lit albeit very dim, the only current path was the meter.

This isn't a high quality fluke meter or anything, just a hardware store branded multimeter. is this normal behavior for cheapo meters?

edit: I never noticed before because I will commonly use a series resistor(10-15 ohm) and measure the voltage drop across the resistor to determine current in a circuit. for some reason I never trusted its ammeter functionality. now I'm questioning if it is even useful as a paper weight.

 

What scale are you using?

Do you have access to a good meter?

 

I noticed this when I removed a wire connecting the cathode of the led I was examining to my surprise it stayed lit albeit very dim, the only current path was the meter.

Perhaps you would describe the connection more fully?

Do you have access to a good meter?

You don't actually need a good meter, just a high value resistance, the 1M - 10M range.
Substitute this for the meter and see if you get the same illumination.
Better, a resitance box would tell you at what resistance the illumination begins to occur and give you an estimate of the input resistance of the meter.
The meter's input resistance is normally set by a resistor so if the one in your meter has gone low for some reason this test will show it up.

 

Typical meters have a input resistance of 10 megaohms on the DC scale, even the cheap ones, so the behavior of yours seems odd.

 

I'm curious about the behavior of common digital multimeters. I understand the concept of meter loading on a circuit, but I never noticed before now. my multimeter seems to be creating a current path between the cathode and anode of my circuit when it is reading voltage. Enough current that it will visibly dim an led when measuring the voltage drop across the diode. it will also even cause enough current to light up an led. I noticed this when I removed a wire connecting the cathode of the led I was examining to my surprise it stayed lit albeit very dim, the only current path was the meter.

This isn't a high quality fluke meter or anything, just a hardware store branded multimeter. is this normal behavior for cheapo meters?

edit: I never noticed before because I will commonly use a series resistor(10-15 ohm) and measure the voltage drop across the resistor to determine current in a circuit. for some reason I never trusted its ammeter functionality. now I'm questioning if it is even useful as a paper weight.

What are you using the ammeter function for? If you are trying to measure current, you must break the circuit and insert the ammeter in series.