Date: Mon, 29 Dec 2003 03:12:04 -0500
Reply-To: Carl Hansen <carl_hansen@IEEE.ORG>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Carl Hansen <carl_hansen@IEEE.ORG>
Subject: Re: What makes a pyrometer's cable so special? - conclusion
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David,
Well everyone is bouncing around the right answer here, but in technical
terms that might not be easily understood so here's a laymans explanation.
I learned the answer 30 years ago when I added a VDO Head Temp Gauge to one
of a string of modified Beetles and/or Loafs. I'm also an electrical
engineer so I guess I'm supposed to know this stuff.
The system is calibrated to work properly with a length of wire AND 3
connections:
The wires ARE two individually different wire TYPES so that a small
potential (or voltage) is generated when the end connection is heated.
Actual length is not so important as is the number of connections.
There are 3 terminals, one terminal at the end that senses the heat (as was
noted by others, typically a soldered joint) and 2 other connections, one +
and one - at the gauge.
If additional connections are added, they also can generate a small
potential (or voltage). The additional potential can throw the calibration
of the gauge off. The potential generated can be millivots at best, hence
the sensitivity to ADDING an additional length of wire..
p.s., if memory serves me correctly, I was able to run the ?14 foot length?
of wire provided by VDO back to the engine compartment of my vans without
having to add lengths of wire, or was it the beetle?? umm, that was a long
time ago..... so I put on a jacket and went out to measure SyncroBeast and
note that 14 foot might be a challange to run to the back.
Ch
carl_hansen@ieee.org
'96 GLX Passat Wagon - they were all green - weren't they?
'87 944 na - RED! needs head gasket & tires (but what a sweet ride)
'89 SyncroBeast Vanagon - parked for the winter - boo hoo
'87 16V GTI - dead, needs rings
'80 850 Yamaha Special - burns oil
'89 16V GTI w/ toasted motor - needs tranny
'99 Beetle - red, red, red (SO's)
New Jursey (Gawd Forsaken State of)
(our hearts remain in MinneSnowta)
In a perfect world without walls or fences........
.....................why would we need Windows or Gates?
........... Only a True Jedi Master can touch the dark side
............ and remain untainted!
We will return... when we get back... from where we are going! Ed
