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Subject: Re: Audio Phase meter cct wanted
Date: Mon, 18 Nov 2002 16:45:24 -0800
X-Mailer: Mozilla 4.78 [en] (Win98; U)
"George R. Gonzalez" wrote:
> "Jeff" wrote in message
> > I need a simple circuit to measure relative phase of audio tones, but more
> > accurately than using scope patterns. Perhaps some sort of audio squarer
> > with phase comparator and meter output. Has anyone seen such a circuit?
> > Thanks.
> > JEFF
> > ZL3TNV
> I made one up a while ago when I needed an accurate 45 degree phase shift
> in a stereo modulator.
> Basically you want to square off the signals, then XOR them, then scale and
> the output. THis circuit is good from about 10Hz to 200KHz.
> Do this twice:
> put a 1 meg resistor from output to input of a CMOS inverter (74HC04)
> feed one input signal into inverter thru a 0.1uf capacitor. Tie output of
> inverter to
> input of next inverter, tie output of that inverter to input of next.
> feed the outputs to a CMOS XOR gate. Feed output of XOR gate to
> 32K resistor. Other end of resistor has 1uf mylar cap to ground.
> Put a 18k resistor across the capacitor. Put a digital voltmeter across the
> The meter will read 0.00 for the signals in phase, 1.80 for the signals 180
> out of phase.
> Hope this helps,
I've been experimenting with phase measurement.
Stick the two signals into the left and right channels of a sound card.
Run a correlation function on the two channels.
The simulation works very well. We'll know in a few days if it works in real
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