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HU output question
Posted: Fri Nov 09, 2007 3:40 pm
by PGsta14me
I feel like I should know this but:
Is the output signal (RCA's) from your HU AC or DC voltage?
Why am I only measuring 168 mV DC on the output when the ratings are supposed to be 4V? I varied the HU volume, but when I turned it up it went to about 150 mV.
Posted: Fri Nov 09, 2007 3:43 pm
by fuzzysnuggleduck
It's sending an analog waveform, not a flat line voltage, so AC.
Posted: Fri Nov 09, 2007 4:01 pm
by stipud
Play a 60Hz test tone and measure A/C to get an accurate reading.
Posted: Fri Nov 09, 2007 4:18 pm
by PGsta14me
That would explain it!
Can that voltage be measured? (My DMM's lowest setting for ACV is 200V and I have no reading, which would probably be expected?)
Posted: Fri Nov 09, 2007 4:25 pm
by Bfowler
it doenst have a millivolt setting or anything either? thats odd because if anything it should be capable of reading the 120V from a regular wall plug in
Posted: Fri Nov 09, 2007 4:29 pm
by stipud
http://www.soundbuggy.com/Eric/Test%20Tones/index.html
Burn those to a regular CD (not MP3)
I normally do...
Track 1: pink noise
Track 2: 1kHz
Tracks 3-24: 60Hz
Tracks 25 and up: corresponding Hz tone
Set it on track 3, turn up the volume on the headunit (disconnect the amp of course), and measure between your RCA center pole and the shield of it. You will probably see about 2v RMS coming out of it, instead of the advertised 4v.
200v just means the limit is 200 volts to read. It should still show 4 volts no problem, though maybe not 4.5553 volts
Posted: Fri Nov 09, 2007 7:13 pm
by PGsta14me
Voltage varies with different frequencies, right?
My DMM is really cheap, so they isn't a mV range. Not to mention the positive test lead was blown off by some idiot trying to measure wall voltage on the current setting. I won't mention any names.
It does still work, and I still have some wire left to use for measuring.
I'll give those test tones a try. Thanks!! Sorry guys, just learning how to do some of this stuff. This is starting to make more sense to me![/i]
Posted: Fri Nov 09, 2007 7:27 pm
by stipud
FYI the reason we use 60Hz is because that's the frequency our household power runs at in North America. This is what most cheap multimeters are calibrated for. Other better (and more expensive) "True RMS" meters should be able to measure regardless of frequency.
Posted: Fri Nov 09, 2007 8:09 pm
by fuzzysnuggleduck
stipud wrote:FYI the reason we use 60Hz is because that's the frequency our household power runs at in North America. This is what most cheap multimeters are calibrated for. Other better (and more expensive) "True RMS" meters should be able to measure regardless of frequency.
Speaking of which, I'm should grab that Fluke meter from work which is True RMS and give that a short on "Min/Max" with music to see what the M44 and M100 are really hitting in real world applications.