How to measure current using cathodrayoscillope(CRO)?

Answer 1

The best way is to get a current probe. This is a non-contact Hall-Effect sensor which is placed around the wire carrying the current you want to measure. The other way is to use a differential voltage probe (or use a dual-channel scope in the difference mode) and measure the voltage drop across a small resistor in series with the current you want to measure. Only if the location of your current measurement is connected to ground potential can you use a single-channel scope with voltage probe and resistor.

Answer 2

I Need more info on the amount of current you need to measure, the voltage of the source, and the A.C. waveform. It is also important to know whether the load is reactive (motors) or resistive. (I assume you are measuring AC). A simple way to measure AC sinewave current is to insert a small resistor in series with the circuit. This resistor should be 0.1 to 1.0 ohm
depending on the expected current, and should be connected on the ground side. Connect the scope ground to ground, and the
input to the other side of the resistor. Measure the peak to peak
voltage of the sinewave, divide by 2, and mutiply by 0.7071
Divide this by the value of the resistor and this will give you your
RMS current. Reactive loads are much more complicated to measure. I use this method, but usually for very small current measurements (milliamps) and use resistors 10 to 1000 ohms.
otherwise, I use a DVM with a true rms volt/current or clamp meter, or phase meter for reactive/ capacitive loads.(very expensive)

Answer 3

You can't measure current directly with a scope. It only measures voltage. Put a resistor of a known value in series with the device you want to measure. Measure the voltage, with the scope, across the resistor. Take that value and divide it by the resistor value and you will have the current. (I=E/R)

Answer 4

yiou use a CRO the same way you would use a amp meter, in series with load, use higher rating on scope then go down to readable value.