Negative Voltage on a PSU

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Negative Voltage on a PSU

Postposted on Sun Sep 01, 2002 2:01 pm

I'm familiar with most AC and DC voltages and how to measure them with a VOM, but what exactly is negative voltage, how does it differ from positive voltage, what's it used for in a computer, and can it also be measured with a VOM?

Thanks for any light you guys can shed on this one!
CTG
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Postposted on Sun Sep 01, 2002 2:35 pm

Well.... a negative voltage in this case is just like any other voltage.
Its a difference in the potential of certain points.

Just as the difference between a +5 and ground is 5 volt... the difference between ground and - 5 is also 5.

If you switch polarity on the Volt meter(multimeter) you also get a negative voltage.

Its all in the reference points.

Well... the difference between +5 and -5 is 10volt so it can be used to get a lot of different voltages from just the 3.3, 5 and 12 volt lines.

And i can think that HD spindle motors use it for something but thats just a guess.
Aphasia
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Postposted on Sun Sep 01, 2002 5:16 pm

The -12V line is also used in serial ports. The -5V line may also be used for Differential SCSI as well.
SecretSquirrel
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Postposted on Tue Sep 03, 2002 9:04 am

Excellent.

Thanks for the info!

:)
CTG
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