Test and Measurement Forum

Hi.

We are using a PicoScope 3206. Since it has an incorporated data logger, we decided to use this to monitor the power consumed of a certain system that we have built up. Unfortunately, as we all know, oscilloscope can not directly measure currents like multimeters do. So we have a problem.

We planned on putting a resistor in series to the system, measure the voltage across the resistor, then do some Ohm's law. But, we are having problems measuring the voltage across the resistor using the PicoScope. Whenever the "ground" of the probe is connected at the other end of the resistor, the voltage supplied to the system suddenly drops. We think it is caused by the 'universal' ground of the scope and the PC.

Any suggestions on how can we measure the current aside from purchasing the current clamps? Thanks a lot.

Hi

Your resistor needs to be in parallel with the scope. Your current should flow through the resistor and you can measure the voltage across it.

Hope this helps

Robin

Robin,

Sounds like that is what he is doing.

xavier,

You can measure the voltage drop across the resistor, but then you will have a voltage potential on the scope ground. If you have other channels deployed, then this will feed through to the other channel grounds.

I suggest you use a current probe:

http://www.picoauto.com/automotive-acce ... lamps.html

_________________
Tom Roberts
(The Picotologist)
http://www.autonerdz.com
skype: autonerdz
THE PicoScope Automotive Authority
In North America

We have exactly the same problem measuring the voltage across a resistor and have 2 channels used thus causing the grounding problem.

Is there another way to solve this grounding problem as we are measuring less that 10 ma sometimes

regards

Andrew

You could use two channels, one measuring each side of the resistor. You could then use a math-channel to calculate the difference i.e. the voltage drop across the resistor.
You could also scale the math channel to give you the current rather than the voltage drop.