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From: "George R. Gonzalez"
Subject: Re: Audio Phase meter cct wanted
Date: Mon, 18 Nov 2002 13:39:11 -0600
Organization: University of Minnesota, Twin Cities Campus
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
"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?
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
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,
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