AC Current Measurement

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** May well be that such meters are required to measure the DC component of any load current - something a current transformer cannot do.

I have a B&D hot air gun that draws 6.7amps at 240VAC on full setting, but drops in series at half power.

It makes any toroidal supply transformers on the same circuit growl when I use it !!

..... Phil

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Correction:

" I have a B&D hot air gun that draws 6.7amps at 240VAC on full setting, but drops A DIODE in series at half power. "

.... Phil

You don't need the entire link for Ebay. Edit from this:

To this:

By removing the description.

or out of (sinking) a node. (The node is the grid and we can either supply or sink current to that node). Measuring current is easy but how do I deter mine which direction it is going. Am I sourcing or sinking?

g my power loss to 0.40 watts, and trying to resolve a 100 mA current chang e in direction, my CMRR would be -128 DB, not easy to do. There has got to be a better way.

Thanks for all your help. I was looking for a simpler solution to a diffic ult problem. If Tesla needed net-metering, then AC might not have been such a good idea. I will bite the bullet and go with a net metering chip that m ust battle the 135 dB CMR problem strait up. Cheers, Harry

icult problem. If Tesla needed net-metering, then AC might not have been su ch a good idea. I will bite the bullet and go with a net metering chip that must battle the 135 dB CMR problem strait up.

Why do you need to have 135dB CMR? Why don't you would optoisolate the output of the measuring cicuit and have the sensitive circuitry at mains voltage?

John

There are isolation amps. And transformers.

Or float the metering circuit on the shunt.

A 135 dB CMRR amp is pretty much impossible.