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Scirocco-l Digest, Vol 16, Issue 68 (Gauges)
You can build an ammeter with a shunt and a voltmeter. The shunt
costs about $14.
Here's a 100AMP shunt:
<http://www.allelectronics.com/cgi-bin/item/SNT-100/search/
100_AMP_SHUNT,_50MV=100_AMPS_.html>
Here's an appropriate meter to use "across" it, also $15:
<http://www.allelectronics.com/cgi-bin/item/
PM-122/385/3.5_DIGIT_LED_PANEL_METER,_200_MV_.html>
You could also use a DMM to on mV range to calibrate a standard VDO
voltmeter into amps to accomplish the
same thing for a more "portable" approach.
==Brett
On Jun 22, 2006, at 10:03 AM, Dan Bubb wrote:
> So, a shunted ammeter uses a shunt!!! ;^)
> A shunt is a high current, low ohm resistor that is put in series
> between the battery and any load you want to measure.
> Then the meter is wired in parallel to the shunt. So, most of the
> current goes through the shunt but some of the current, in
> proportion to the ratio of the shunt resistance to the meter
> resistance, goes thru the meter.
> Sounds like a cleaner solution. Unfortunately, a shunted ammeter
> costs about 4 times what a normal ammeter costs!
> Does anybody care about this?
> Dan
>
>
> From: Dan Bubb" <jdbubb@verizon.net>
> To: "GGehrke" <ggehrke@gmail.com>
> Cc: <scirocco-l@scirocco.org>
> Sent: Thursday, June 22, 2006 9:39 AM
> Subject: Re: Scirocco-l Digest, Vol 16, Issue 68 (Gauges)
>
>
> This is my take on an ammeter. All the current needs to go through
> the ammeter for it to measure it. But, I doubt you'd want to
> measure the starter motor draw. That might be enough current to
> melt the ammeter and the wires that run to it. So, you need to
> leave the starter out of the ammeter circuit, but you want to
> include everything else including the alternator output.
> So only the starter motor would connect directly to the positive
> terminal of the battery. All the other connections to the + battery
> terminal would get moved to one side of the ammeter, the alternator
> output would be moved from the starter motor connection to the
> ammeter and the other side of the ammeter would connect to battery +.
> OTOH, there is something called a shunted ammeter. I have no clue
> how that works, but wouldn't mind finding out!
> Dan
>
> From: "GGehrke" <ggehrke@gmail.com>
> Sent: Thursday, June 22, 2006 9:08 AM
> Subject: Re: Scirocco-l Digest, Vol 16, Issue 68 (Gauges)
>
>
>>> Ammeter, you can tell if the Alt is charging correctly or not.
>>> The needle is centered at 0. When you turn the key or put on a
>>> load it swings to the left. When charging while the engine is on,
>>> it swings to the right.
>>
>> Ah, that makes sense now. I have an ammeter gauge that I pulled at a
>> junk yard but wasn't sure how to hook it up because ammeters have to
>> go in series. Surely I couldn't run the car's main power through it,
>> but I figured about the best usage of it would be to monitor some
>> arbitrary system like the headlights or something.
>>
>> But where exactly do you hook it up? I'm assuming the blue exciter
>> wire, right? Cause I know that's what causes the alternator light on
>> the dash to work...
>>
>>> Vacumn shows the manifold air pressure. Are you using a lot of
>>> fuel or running economically (or have a leak in the 25 YO rubber).
>>
>> My BMW has this and literally labels it a "MPG" gauge. It's one of
>> those things that's just kinda interesting to watch. I think I have
>> one for my scirocco that I'm going to install if I ever get around to
>> working on the car and not just school stuff :-/
>>
>> -Grant-
>>
>>
>>
>>>> -----Original Message-----
>>>> From: Chris Effinger [mailto:chriseffinger22@hotmail.com]
>>>> Sent: Saturday, June 17, 2006 12:52 AM
>>>> To: scirocco-l@scirocco.org
>>>> Subject: RE: Scirocco-l Digest, Vol 16, Issue 68
>>>>
>>>>
>>>>
>>>> has anybody put in aftermarket mechanical gauges ( water
>>>> temperature, oil
>>>> pressure)?, wondering if there's an easy way to do it. my 81s
>>>> originally had
>>>> some sort of electrical gauge
>>>>
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>>>
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>>
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>
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