question on misuse of a multi meter

[henrylrjr]

What would happen if a multi meter is mis-set to check resistance while being used to check voltages on a chip amp like the Modulus86. Items being checked would be were transformer wires connect to power supply and power supply to amp pcb power input connections. Obviously, in order to check voltages, the amp would be plugged in and turned on.

Thanks,
henry

 

[DUG]

Depends.

What multimeter brand/model?
Fixed scale or auto?
Does it have protection for this error?
What voltage was it subjected to?

Simple answer:
Does it still measure resistance accurately to full scale?
If not it is damaged.

 

[henrylrjr]

One is a Micronta analog and the other is a Velleman digital. I tested both meters for AC, at a 120V outlet and with a 9V and 1.5V battery and they were both accurate. I also tested both for resistance and both are accurate. I was concerned because the 5A slow blow fuse in the amp's AC entry module blew.

I put in a new fuse and things seem back to normal. What could have caused the fuse to blow?

 

[JMFahey]

You shorted 2 points which were not meant to be connected together.

 

[tomchr]

I was concerned because the 5A slow blow fuse in the amp's AC entry module blew.

What were you measuring when the fuse blew? What were the settings on the meter and what did you stab the probes onto?

Tom

 

[henrylrjr]

I didn't realize, right away, that the fuse blew. Not even sure what meter I was using or were the probes touching.

I just decided to check the duplex 10amp wall outlet and the found the receptacle for the round grounding prong, on a three prong cord, is not connected. I know I was testing some of the connections for voltage with one probe on the earth ground lug screwed to the case bottom. I'm thinking that, since there was no path to ground, that may have caused the fuse to blow. Maybe I didn't have the meter set incorrectly. I was trying to remember to turn of the amp off every time I was checking resistance.