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Frank Berry 9th June 2011 07:22 PM

Absolute phase test audio for transformers
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I have a number of transformers and needed to see the absolute phase of each transformer winding.
In the past, I've applied low voltage ac to one winding and compared the phase of the other windings with that voltage.
I've come up with an easier and faster method of measuring the absolute phase of the transformer windings.

Using Adobe Audition, I generated a 120Hz sine wave with alternate positive-going portions of the sine increased in level by 10dB.

When I feed this waveform into one of the transformer windings, I connect an oscilloscope to the other windings (one at a time) and can clearly see the absolute phase of the winding as compared with the input winding.

DF96 9th June 2011 08:15 PM

Measure the inductance with the windings in series, both ways round. The larger inductance is when they are in phase.

Frank Berry 9th June 2011 08:45 PM

Why bother with measuring the inductance when you can instantly see the phase using this waveform?

Enzo 9th June 2011 08:51 PM

Nothing wrong with your scope method. His inductance method requires no application of a waveform. A hand inductance meter will do it quickly. Nothing wrong with having a number of ways to do it.

DF96 9th June 2011 09:40 PM

I reckon attaching a DMM or other inductance meter is quicker than using software, but each to their own.

Frank Berry 9th June 2011 09:46 PM

No it's not quicker. By applying audio, you can instantly see the phase without the need of reversing the transformer connections.
There is no software either. I used the software to create the waveform and burned it to a CD. I merely play the CD and feed the audio into the transformer. It's fast and accurate.

simon7000 9th June 2011 09:46 PM

Your phase test will also work for everything from amplifiers to loudspeakers.

Frank Berry 9th June 2011 09:48 PM

Yes it will. I discovered that one of my amplifiers inverts the phase. I didn't know that until I played the CD through the amplifier.

simon7000 9th June 2011 09:54 PM

If you are up to it a really handy test CD would be that waveform repeated for several octaves, say 20 to 20K. As a wave file it could be easily transported and would check crossovers etc.

DF96 9th June 2011 10:07 PM

Is your oscilloscope always handy near your CD player? Mine isn't even in the same room! I find a DMM is more portable than a CD player and 'scope. Anyway, as I said, each to their own. Sorry for raining on your parade. 8-)

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