Thread: DIY Data-Logger
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Old 07-21-09, 01:07 PM   #8
NiHaoMike
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Quote:
Originally Posted by AC_Hacker View Post
I also wanted one of the eight analog inputs to the data logger to measure power if I was testing a newly-built heat pump, for instance. I decided to use a toroid transformer, with the primary coil being the power line that conducted current to the heat pump. The secondary would then have a current induced into it that was proportional to current in the primary. Then I would rectify the AC and use a voltage divider to bring the voltage to a mid range between 1 an 3.4 volts.
Actually, the voltage output is proportional to the derivative of the current. You'll need to integrate the output in order to get meaningful measurements if the load is not linear. Or use a hall effect current sensor which outputs a proportional signal.

And try adding capacitors to reduce the noise.
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