Measuring current and voltage using PicoLog 1000

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encepence
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Measuring current and voltage using PicoLog 1000

Post by encepence » Wed May 20, 2020 9:37 am

Hello,

I would like to ask if it's possible to measure voltage and current at the same time?
I have Picolog 1000 with Small Terminal Board.

Martyn
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Re: Measuring current and voltage using PicoLog 1000

Post by Martyn » Wed May 20, 2020 9:41 am

What are the currents and voltages that you are trying to measure ?
Martyn
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encepence
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Re: Measuring current and voltage using PicoLog 1000

Post by encepence » Wed May 20, 2020 11:06 am

Hello Martin

Thanks for your answer. I want to measure approx. 1.3V DC voltage and 0,025A current

Martyn
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Re: Measuring current and voltage using PicoLog 1000

Post by Martyn » Wed May 20, 2020 11:43 am

Please reference the Terminal Board User Guide which will explain how to do this.
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encepence
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Re: Measuring current and voltage using PicoLog 1000

Post by encepence » Wed May 20, 2020 12:21 pm

I already read it and I'm not sure if I understand it properly.
Could you see picture below and tell me if presented connection is good?

I'm almost sure it's not because all grounds on terminal board are connected each other. But I have no idea how to connect it in different way. Could you modify this circuit showing proper connection?

Thanks.
Attachments
connect picoscope.jpg

bennog
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Re: Measuring current and voltage using PicoLog 1000

Post by bennog » Wed May 20, 2020 4:49 pm

See below modification of your image.
2020-05-20_18-44-29.png
Benno

Martyn
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Re: Measuring current and voltage using PicoLog 1000

Post by Martyn » Thu May 21, 2020 5:30 am

Using the bennog modification to the circuit fit the resistor in position R4 on the terminal board to measure the current in Ch2. However this will cause the ground level on your device to rise, V = I*R so the resistor needs to be small enough so as not to cause a problem, but big enough so the voltage at your device end can be measured.
Martyn
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encepence
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Re: Measuring current and voltage using PicoLog 1000

Post by encepence » Thu May 21, 2020 6:56 am

Thank you very much for answers!!

I just want to ask one more question to be sure:

The user's guide says about calculating the resistor value. R = 2.5V / Imax
Where Imax is the highest current you want to measure.

So when I know that Imax will be approx 2mA = 0.002A, the resistor which I must use will be about 100 Ohm's, am I right?

And when I connect everything together I have to use math channel where I do Ohms law? So I wil define Current as Channel2/100 and pico soft should draw me nice current graph?

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Re: Measuring current and voltage using PicoLog 1000

Post by Martyn » Thu May 21, 2020 9:57 am

Putting a resistor in the ground return path in this way this means you can't select a value to give access to the full 2.5V input range of the logger as this would raise the ground potential on your device by 2.5V (not good).

It needs to be a small value resistor to give a minimal voltage drop but one which can be read by the logger. If this is not possible then it is probably not the correct approach for you.
Martyn
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