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AC current can be converted to AC voltage by using a shunt resistor. This voltage can be processed by Analog Devices AD636 true RMS to DC converter ( **broken link removed** ) ... and dc can be measured and displayed by anythig you like.
The voltage across a resistor will always be in phase with the current through the it. That means the voltage you measure across the shunt is a true representation of the current through it.
Thus, all you need to do is convert that voltage to a DC voltage. That will correspond to the RMS value of the AC current.
But, probably Nicholas wants to know how the True RMS Clamp Current Meter works so that it can measure true rms current.
Discussing about shunt resistor: to which component/part do we shunt the resistor? To the current transformer? or to the load? or the source? In my understanding, I think it should be the CT ..... am I right or wrong?
yes , I was wondering how to measure the AC high side RMS current using the uC in circuit. Then the uC can do some current limiting job. Thanks you all guys. Do helped me.
Well, I was just wondering if any instrument could measure the curent in parallel (exception of clamp meters) or it is inevitale to break the circuit and measure it in series...
If you want to measure current you must break the circuit and place there an amper meter. Placing a resistor in series of a circuit element and measuring voltage accross resistor is the same thing. Amper meter has very low resistance and voltage drop on it is very low. There exist no method to measure current accross circuit element, in this way you can measure only voltage drop on it. Current can be then calculated if you know the element impedance.
Won't the current change if I place the resistor in series ?
Or are you telling me the equivalent circuit of an ammeter ?
I figure out that no instrument can measure current passing through a compont unless placed in series. And if the current is AC across a reactive component, then I guess there is no way to find it without a clamp tester...Or is there ?
Placing ammeter or series resistor in circuit it can change circumstances if it has high impedance comparing to branch impedance, let's say it should be 1% of it or less. Placing a resistor is equivalent to ammmeter. Current transformer is nothing else but ammmeter. Clamp is allso an ammeter. There is no instrument that does not disturb the circuit behaviour. Question is only how much it changes circuit parameters.
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