Clamp On Amp Meter

[Mark-VA]

When measuring coil current, can you use a clamp on amp meter around the cable?

[boilcoil]

Transformer clamp amp meters can measure only alternating current and have frequecy restruction. The Hall sensor amp meters can measure AC and DC.

[Mark-VA]

This would be to measure the current going to the coil on a White's TDI coil.

[waltr]

When measuring coil current, can you use a clamp on amp meter around the cable?

No, that would put both conductors with opposite currents inside the Ammeter clamp and total current is then zero. Even if it could measure to current of the pulses which it can not.

The best way to measure Coil current in a PI detector is put a scope across a resistor that is in series with the coil. This would be R4 on a TDI. Then measure the Voltage drop acroos the resistor during TX ON and Ohm's law to calculate current.

[rickb]

clamp on current probes are available for scopes and meters. Just put a single turn/lead from the coil through the probe. Look up current transformers. Something that works for 60 Hz will not be accurate for detector freqs. You can make your own with a surplus toroid wound for audio freqs.

[waltr]

clamp on current probes are available for scopes and meters. Just put a single turn/lead from the coil through the probe. Look up current transformers. Something that works for 60 Hz will not be accurate for detector freqs. You can make your own with a surplus toroid wound for audio freqs.

Correct, only one conductor to or from the coil and use a Scope since you need to measure DURING the TX PULSE.

[Carlos]

to calculate the current flowing through the coil, it is calculated as follows: the supply voltage is multiplied by the time of the coil pulse and that value is divided by the coil inductance value. Ej: 12Vcc, 120uS and 320uH= 4,5 Amp.

[green]

to calculate the current flowing through the coil, it is calculated as follows: the supply voltage is multiplied by the time of the coil pulse and that value is divided by the coil inductance value. Ej: 12Vcc, 120uS and 320uH= 4,5 Amp.

If coil and circuit resistance is zero ohms

[dbanner]

Simplest way is to measure battery current with coil connected and then without the coil. Subtract the two results.
This would be RMS value, which is what you want to make a bunch of other useful calculations.
Does anyone know the coil parameters for White's dual field search coil? Particularly the value of the internal damping resistor for smaller coil. Edited.

[bklein]

Im not impressed with the DF coil so wouldn’t use it for an example. Ive tried two of em.

[dbanner]

You're right.I got a bit drifty there.
A mono coil would suffice. Problem is pulse width affects the whole thing, so making theoretical calculations is not so easy unless you are like professor of mathematics. Also, counting divisions on old analog screen is not for the faint hearted.