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measuring current using PicoScope

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measuring current using PicoScope

Postby xavier » Fri Nov 28, 2008 6:33 am

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.
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Postby Robin » Fri Nov 28, 2008 12:58 pm

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
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current

Postby Autonerdz » Fri Nov 28, 2008 4:20 pm

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

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Re: measuring current using PicoScope

Postby Andrew » Wed Nov 04, 2009 11:35 am

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

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Re: measuring current using PicoScope

Postby Erik » Wed Nov 04, 2009 2:29 pm

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.
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Re: measuring current using PicoScope

Postby Dome1985 » Tue May 27, 2014 10:19 am

Hello all,

I also have exactly the same problem measuring the voltage across a resistor. (R_shunt = 0.15 mOhm)

Also the idea to use 2 Channels of the PicoScope (3000 Series), it still doesn´t work.

Anybody an idea?

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Re: measuring current using PicoScope

Postby Hitesh » Mon Jun 02, 2014 10:33 am

Hi Dome1985,

We recommend using using two channels - you can then apply a DC offset to each channel to set them to 0V without any voltage applied then subtract the difference using a maths channel.

Ensure that you are using an appropriate voltage range as well.

Regards,
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