ADC 16 to measure current

 
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scottlynn
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PostPosted: Thu Jan 30, 2003 1:27 pm    Post subject: ADC 16 to measure current Reply with quote
Hi,
I was hoping that I could use the ADC 16 to measure the current flowing bewteen two electrodes in an electroplating cell. I have looked at the info on the website but I'm not that great with circuit diagrams.

Whats the procedure for selecting the resistors (and fitting them) that have to be wired into the terminal board (which I also have), I'd only be working with potentials around 1V and currents of around 8mA.

As I said, I am hopeless with circuit diagrams and electronics, so if you could help with an idiot's guide to setting this up I'd be grateful!!

thanks
scott
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scottlynn
Guest
PostPosted: Thu Jan 30, 2003 1:28 pm    Post subject: almost forgot Reply with quote
how do you turn the measured voltage into a current reading as well?
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matthew
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Joined: 25 Sep 2002
Posts: 133
Location: Cambridgeshire, UK
PostPosted: Fri Jan 31, 2003 12:27 pm    Post subject: 0(4)-20mA Sensors on an ADC-16/ADC-11 Reply with quote
Hi Scott,

I'm afraid you'll have to do some maths!
Code:
Resistance = Voltage / Current
Therefore you will need to know the voltage drop and current that you need to draw across a resistor in order to determine the value you require. I will give you a common example which is used to adapt the ADC-16 or ADC-11 for 0 to 20mA sensors (usually 4 to 20mA actually).

We know that the ADC-16's maximum voltage input is 2.5V and that this should correspond to the maximum current which we know will be 20mA.
Hence:
Code:
Resistance = 2.5 / 0.02 = 125 Ohms

Make sure that you choose a resistor that is low enough not to interfere with your current circuit too much though.

Just use the same V = I x R equation to work out the look up table to convert the voltage reading back into current (the help files from Help|About detail how to do the scaling in software).

Best Regards,
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