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  1. #1
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    How can I measure AC current with ~500 kHz frequency?

    I plan to measure the output from an electrosurgical generator.

    1. According to the user manual, the current output is AC current with ~500 kHz frequency and ~0.3 A amplitude.
    However, most digital multimeters have lower bandwidth than 500 kHz.
    How can I measure this current output? Do I have to use another measuring device instead of multimeter?

    2. Voltage output is thousands of Volts with ~500 kHz.
    How can I measure high voltage like this?

    Thank you.

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    Re: How can I measure AC current with ~500 kHz frequency?

    A multimeter is not going to work at 500khz. I think you want to look at a current transformer. Without further information, it’s difficult to make a suggestion. Is this for occasional measurement? Permanent monitoring?

    To measure high voltage, you would use, um, a high voltage meter. Or, you can get a HV probe for your multimeter. But BE CAREFUL!! You can kill yourself, or worse, damage the equipment.



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    Re: How can I measure AC current with ~500 kHz frequency?

    Thank you for your reply.
    This is just for occasional measurement.
    Could you explain little more about measurement using current transformer?
    And, if I get a HV probe, can I measure voltage over the maximum voltage of my multimeter?
    Thanks!



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    Re: How can I measure AC current with ~500 kHz frequency?

    Oscilloscope is the best instrument to measure voltage, current and frequency.
    Use a current probe to measure the current and a high voltage probe to measure the voltage
    Be carful because you are dealing with 1000V, it is very dangerous to human.
    If your probe do not have 1000V rating you can use resistor divider across the 1000V and you will get half of the voltage through resistor divider. (for example 50M OHM +50M OHM)



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    Re: How can I measure AC current with ~500 kHz frequency?

    If your probe do not have 1000V rating you can use resistor divider across the 1000V and you will get half of the voltage through resistor divider. (for example 50M OHM +50M OHM)
    Voltage dividers have to be compensated for high frequency measurements.

    There are a few high performance benchtop DMM with MHz frequency range. But they are usually missing a high frequency input impedance specification, thus they can't be well operated with external voltage divider. Internal DMM current shunts are generally not suited for > 10 kHz frequency range.

    Oscilloscope with high voltage probe and current transformer or coaxial shunt is the way to go. Voltage probe has to be rated both for peak voltage and rms voltage at the applied frequency.



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    Re: How can I measure AC current with ~500 kHz frequency?

    try a pearson current transformer

    https://www.pearsonelectronics.com/p...rrent-monitors



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  7. #7
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    Re: How can I measure AC current with ~500 kHz frequency?

    making your own CT on a suitable ferrite toroid, with a suitable burden resistor ( non inductive ) and a good 'scope will allow you to measure accurately and in an isolated fashion ...



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