I have researched this on google this for 3 days and absolutely cannot learn the answer!
Some multimeters that are certified CAT III 600 VOLT rated have 2 inputs and some have 3. With 3 inputs, 2 are dedicated to measuring AMPS. These 2 are fused. With 2 inputs, one input combines the amp and voltage inputs.
With 3 inputs, the voltage input does not have a fuse. With 2 inputs, the voltage input does have a fuse.
A certified CAT III 600 VOLT meter can safely sustain transient surges up to 6000 volts. A fuse is not needed on the voltage input to do this. It uses ptc thermistors or whatever else for overload protection.
From what I can gather, a fuse does not blow from voltage alone. It blows from heat which is created by voltage AND amps. And the voltage rating on a fuse only pertains to how much voltage an already blown fuse can handle before arcing. So it makes sense to me that a transient voltage surge would not blow a fuse when properly measuring voltage because current is not flowing through the meter. Is this correct?
Does a meter with 2 inputs have overload protection besides fuses like a meter with 3 inputs does? Obviously a fuse is not needed on the voltage input. So when there is a fuse on the voltage input, does a voltage surge blow the fuse?
I think this is a simple question really. I'm asking about the differences in how the two different types handle transient voltage surges. I am well aware that sticking the leads into a wall outlet while on the amp setting will blow a fuse. That has nothing to do with my question. Thank you MUCH for any help or insight you can offer.