I have accidently taken readings of resistance on my digital multimeter on live mains and now the resistance function on my meter is not working. But i'm still able to use other functions in it. Is there a possible fix for it? I know that the multimeter is fused, why did'nt the fuse go off?
Electronic – Accidently read resistance on live wires
multimeter
Related Solutions
I'll assume you don't have or can't find a schematic for it (if you do let us know) so:
First thing is to open it up and take a look around the input circuitry, something blown/shorted may be easy to spot visibly (as Jim mentions any protection components are a good bet)
If the rest of the functions are still working, it may be just the continuity circuit which is damaged - if this is the only function which requires the buzzer on the meter, tracing back from the buzzer to any driving circuitry may prove helpful.
When multimeters are in resistance testing mode, they connect their battery to the output through a high resistance (maybe in the order of 200kOhm if not higher), and then measure the effect that the load has on the voltage - if the load is very high resistance, it will read close to the full supply voltage, if the load is very low resistance, it will read close to zero.
What this means is that if you connect a voltage source to the input in this mode, it should do no harm at all (unless it is out of range of what the DMM is specified for, which 4V or so definitely wont be) because the high resistance of the internal voltage source will limit any current flow.
TL;DR; no you won't have done any damage.
Update:
Even though this is the schematic of a fluke 87 multimeter, yours will likely be very similar. I've highlighted the switches that are closed for resistance measuring mode, and also for reference the high resistances that are protecting the input (and will mean you have not done any damage):
Best Answer
There are two kinds of mulimeters. Good ones and ones that better work as a drink coaster.
A good meter is designed to survive connecting the resistance function to mains (live wiring). Bad meters usually do not survive.
The fuse in the meter is only designed to protect the current measurement function. Once the meter is damaged there is usually very little or nothing you can do to fix it.