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Measuring Ultra-Low AC Power

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Joined: February 11th, 2019, 6:29 pm
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Measuring Ultra-Low AC Power

Post by nikhil9dua » February 11th, 2019, 6:35 pm

Hi there,

I have an AC-DC rectifier for which I'm trying to measure efficiency for. The input to the rectifier is a 13.56 MHz signal which hovers around 2.8V Rms. The output is just essentially a DC Rail which sources a certain amount of current.

My goal is to measure overall efficiency (DC_Power_Out / AC_Power_In). I am able to measure DC_Power_Out without a problem using a current source circuit, multimeter and a current measurement circuit. However, I'm not sure what the best way is to measure AC_Power_In

The rectifier takes in <2mW of AC power. What is the best way to measure this AC power going into the rectifier with Tektronix solutions or any solutions per se? I have tried using a CT-1 AC Current probe however this is quite sensitive since input currents are in the range of hundreds of uA to few mA. Another issue is the timing between the voltage and the current due to phase lag doesn't allow for accurate AC power measurement.

Any ideas & solutions are much appreciated!



Andrea C
Keithley Applications
Keithley Applications
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Joined: October 15th, 2010, 10:35 am
Country: United States

Re: Measuring Ultra-Low AC Power

Post by Andrea C » February 13th, 2019, 5:21 am

Is the 3% accuracy of the CT-1 ok, if you could read the 5mV/mA signal with better vertical resolution?

Contact your local account person and ask about MSO64 and default power application capability. If you allow scope to measure V and I, we can give you the power info.

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