Scirocco-l Digest, Vol 16, Issue 68 (Gauges)

[jdbubb at verizon.net (Dan Bubb)]

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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