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Measure burden resistor of a current transformer

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heinthetaung

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Hi

I have a current transformer with burden resistor fixed to it and it is connected to differential amplifier circuit then connects to ADC of a microcontroller. Is it possible to measure the resistance of the burden resistor using the connected ADC? I have different current transformer with different burden resistor, I want to know which current transformer is connected to the circuit.

CT is to measure 50Hz AC current.

Since the CT is ac current source and burden resistor is a load resistor connected to it, how can I measure the source impedance of the CT?

Thanks.
 

If you do not have the main current conductor through the centre, just apply a high frequency audio voltage to the connections. The actual inductance will have a high impedance leaving the resistor to take the current. I would do it at several spot frequencies to insure you get consistent results. Say 2KHZ, 5 KHZ, 10 KHZ.
Frank
 

You might be able to use the ADC depending upon it's sample rate and how the differential amplifier is connected.
Instead of using AC, you could apply a step voltage to the burden resistor through an external adjustable resistor (pot).
You adjust the pot until the ADC measured initial peak of the pulse voltage is equal to 1/2 the applied pulse voltage.
The burden resistor is then equal to the pot resistor setting.

But it all then depends upon the ADC being fast enough to catch the initial peak voltage before it decays significantly from the LR exponential decay due to the inductance of the current transformer.
 

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