# Which current can a multimeter measure for an indefinite duration?

It might vary, depending on multimeter.

But if on a multimeter, there is printed "10A for 30sec. MAX every 15 min" or "20A for 15 sec (time unspecified)", below which approximate threshold is the safe duration of measurement indefinite?

• It should be written on the user manual – Damien Dec 18 '18 at 12:26
• @Damien My user manuals do not mention it. Is there any approximate way to calculate that indefinite measurement current? (at approximate room temperature) – neverMind9 Dec 18 '18 at 12:30
• There is no easy way to calculate that as it depends on many unknowns like: thermal resistance from current shunt to room, allowed temperature of shunt and multimeter etc. If the value isn't listed in the manual but you need to measure a large current continuously then 1) get a meter that does specify this value or 2) get a clamp meter, it measures the magnetic field generated by the current, so there is no power dissipating shunt resistor. – Bimpelrekkie Dec 18 '18 at 12:34
• or an external shunt resistor. – Damien Dec 18 '18 at 12:40

## 1 Answer

Here's an approximation. The answer is probably too low.

30 sec every 15 min is a 1/30 duty cycle. So assume 10A dissipates 30 times what the meter can handle continuously.

Power dissipated in a resistor is proportional to current squared.

So we would get the same average power with a current of 10 (1 / √30) amps = 1.8A

• Too low is better than too high ;-) – neverMind9 Dec 18 '18 at 15:28