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measuring the current draw

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soundman

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Hello guys,

What are the methods of measuring the current draw of a center taped transformer by a meter??

Thanks
 
Hello guys,

What are the methods of measuring the current draw of a center taped transformer by a meter??

Thanks

When you measure current (AC or DC) you need to place the measuring device (meter) in series with the load. You don't mention a load? The fact that you mention a center tapped transformer leads to confusion. Whart exactly are you trying to do? Do not place a meter set to measure current accross any source! Bad things will happen.

Ron
 
Connect the meter in series with the primary coil.

What's connected to the secondary?

If it's a non-linear load, i.e. anything but a motor or a light, you'll need a true RMS meter to accurately measure the current.
 
Connect the meter in series with the primary coil.

What's connected to the secondary?

If it's a non-linear load, i.e. anything but a motor or a light, you'll need a true RMS meter to accurately measure the current.
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That's the only method I was thinking about, but what about the secondary? The secondary is connected to a split 7915 &7815 and finally to 2 Op-Amps, And because I have 3 wires out of the secondary coil of the transformer then I have no idea how to exactly measure the WHOLE current draw of the circuit (Yea, I do know how to use an Ameter In a circuit).
 
You need a true RMS meter connected in series with the primary coil, it is the only way to measure the current consumption of the entire circuit.

You could measure both the positive and negative currents but the won't give you an indication of the power lost in the transformer.
 
2 other questions, an AC CURRENT/VOLTAG meter measures RMS values, So what do you mean by using a true RMS meter??!
The second question which now arrived is I have 2 options, One is measuring the AC current at the primary and the second is to measure DC current values at the Output of the transformer, One option gives me an RMS value and the other a DC value, right, If so how to translate these values whit each others?
 
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That's the only method I was thinking about, but what about the secondary? The secondary is connected to a split 7915 &7815 and finally to 2 Op-Amps, And because I have 3 wires out of the secondary coil of the transformer then I have no idea how to exactly measure the WHOLE current draw of the circuit (Yea, I do know how to use an Ameter In a circuit).

I don't need to know the power lose of my transformer, Just want to know the power consumption of my circuit.
 
if you measure the ground you won't get far I think, you will basically be measuring ac if the two halves of the circuit are drawing the same current alternatly (for example your amplifying a symetrical AC signal), if your circuiit is drawing current from both sides wou will be measuring the difference. if this is you idea of measuring two currents with one meter you will come unstuck
 
The problem of measuring the current into the primary is that the power factor of a lightly loaded transform sucks! The current lags the peak voltage by as much as 60 or 70 degrees, so if you multitply Line voltage by primary current, you will get an artificially high power. It would take a "power meter", or a o'scope reading of voltage/current simultaneously to determine the relative phase of the current to the voltage.

If you do not care about power losses in the transformer or regulators, then measure the DC load current right at the output of each regulator. The load power calculation is trivial there...
 
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I don't need to know the power lose of my transformer, Just want to know the power consumption of my circuit.

Then measure the current taken by both the positive and negative rails.

Ideally you'll need a true RMS meter because the current won't be steady, even though it's DC.
 
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