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Old 05-23-2003, 06:45 AM   #1
yeng
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Default autometer voltmeter: where to ground best?

just got a Phantom voltmeter, im thinking of connecting (+) to cegaratte lighter, and dont know where should i ground best....

I have seached and they were way too many grounding discussion. Why grounding so important?

btw i bought the guage 2nd handed and i just want to install it for experience sake.

Thankx for your help!
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Old 05-25-2003, 01:45 PM   #2
prelude/2.5rs
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Default

Just find a bolt that actually bolts to another piece of metal(preferably the chassis), scuff up the paint a little(paint may interfere w/ connection), loosen the bolt, strip the (-) wire, wrap it around the bolt, and tighten the bolt down. Your gauge is now grounded Good luck!

Mike
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Old 05-25-2003, 02:47 PM   #3
Alan
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As a voltmeter draws little current you don't have to be particular about where you ground to as long as it is connected to something on the body/chassis. If you are going to connect to the positive at the cigarette lighter, why not use the ground there also!
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Old 05-27-2003, 12:38 PM   #4
satrya
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Default importance of grounding

Quote:
Originally posted by yeng
Why grounding so important?
Connecting to a proper ground is as important as connecting to a proper "signal", be it the positive terminal of a battery, or a signal coming out of a gauge signal sender. The reason is whatever instrument that reads the "signal" and ground takes the difference between them.

For a voltmeter gauge, in which you're only interested in how the battery voltage slowly varies, proper grounding (and/or proper positive terminal) contact is not too critical.

However, for some other fast, time varying signals that an ECU reads for example, it is crucial to have proper signal and ground contact. Otherwise, other elements could contaminate this signal, giving it unwanted and excessive noise. Noise is considered in the ECU software design/coding, but there's a certain limit to how much noise can be "rejected" if the signal-to-noise ratio is too low.

In short, when an instrument needs to read a fast signal, the better grounded the wiring is, the better the signal quality is. Of course, it would be very annoying if a poorly grounded voltmeter gauge shows needle vibration due to signal noise, but it won't affect anything critical.
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Old 05-28-2003, 12:54 PM   #5
OKRS25
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Default Re: importance of grounding

Quote:
Originally posted by satrya

Connecting to a proper ground is as important as connecting to a proper "signal", be it the positive terminal of a battery, or a signal coming out of a gauge signal sender. The reason is whatever instrument that reads the "signal" and ground takes the difference between them.

Current flows from negative to positive, so technically your "Signal" is coming from the ground, not the power cable...
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Old 05-28-2003, 01:42 PM   #6
satrya
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Default Re: negative

Quote:
Originally posted by OKRS25
Current flows from negative to positive, so technically your "Signal" is coming from the ground, not the power cable...
That's one of the funny things about electronics. The negative charge of electrons make things seem reverse when compared to other domains. I've gotten used to analogies in other domains (thanks to linear graphs) that it becomes easier to think of current as flowing from positive to negative, and completely ignored the physics explanation.
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Old 05-28-2003, 02:00 PM   #7
OKRS25
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Tell me about it, being an Aircraft electrician, one of the hardest things to do is to explain to someone why it flows from negative to positive, they have a hard time picturing the currenting coming from the ground instead of the wire hooked up to the battery...
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