Sorry, John, beg to differ here. Any transformer having current in the

primary will induce a voltage in the secondary. There is no need for a

burden resistor. OK, I know there's no such thing as an infinite impedance

measuring device, but a 200 meg input DVM is reasonable approximation, and

I've used one of those with Rogowski coils before now .......

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I suspect that if you were to use a current transformer with an unloaded

secondary in this application you'd be in for a nasty surprise!

Let's take, for example, a current transformer with a 1000 turn

secondary and a single turn primary (an unlooped wire going through the

center of the toroid) with 50A going through it. Since the turns ratio

of the transformer is 1000, 50A flowing through the primary will try to

induce 50/1000 = 50mA in the secondary. So, since E = IR and the

unloaded secondary looks like an open circuit, the voltage induced in

the secondary will be E = IR = 0.05A*infinite ohms = infinite Volts!

Looking at it a little more realistically, with your 200 megohm load on

the secondary the voltage would only rise to 5.0E-2A * 2.0E11 ohms =

1.0E11V = 100,000,000,000V, but it might still be a good idea to load

the secondary down a little more heavily to get the voltage down to

where your meter can measure it on a more conveniently available range.