# Measuring current

1. Feb 21, 2010

### taupune

Hi people, i got a question regarding current measurement.
Is there a way to measure it, other than by putting the ammeter in series?
How do they find the current output from one IC to another IC and there isnt any resistance or cap between them?

Thank you.

2. Feb 21, 2010

### skeptic2

The current into the input is simply a function of ohms law. As long as the reactive part is not significant, if the output voltage is known and the input impedance is known, one simply divides the output voltage by the input resistance. If the reactive component is significant, one still divides the voltage by the impedance but the calculations are more complex.

3. Feb 21, 2010

### f95toli

One way to measure currents between ICs etc is to use probe which measures the current "indirectly" via the magnetic field. The accuracy isn't great, but it works

This is also a very commong technique when dealing with higher currents through e.g.; you can buy so called current clamps that can be be with an ordinary multimeter.

4. Feb 21, 2010

### Topher925

Really, the best way is to use just to use a shunt resistor and measure the voltage across it. Hall effect sensors can work as well but are typically very inaccurate as f95toli said. Since you mentioned that you want to measure current going to ICs, i.e. milliamps, your only practical choice is to just use a shunt resistor.

5. Feb 21, 2010

### 0xDEADBEEF

I suspect that he is referring to ICs already soldered onto a board

6. Feb 21, 2010

### sophiecentaur

I don't think Hall devices are any good for measuring a few milliAmps, which is the maximum that the typical circuitry uses 'between devices. mA of AC is fine to measure but DC is a problem because the ambient field is significant and can't totally be 'zeroed out'. If you have a fault, you can normally deduce what's going on without having to know the currents between all components - Kirchhoff 1 will often tell you.

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