Military-Vehicles: RE: RE: [MV] M-37 Gas Gauge

RE: RE: [MV] M-37 Gas Gauge

Alan Bowes (alan_bowes@phast.com)
Thu, 21 Aug 1997 11:17:58 -0600

I haven't taken the fuel gauge apart on my M37, but the VAST MAJORITY =
of other fuel gauges that I've seen use nichrome wire wrapped around an =
insulated bi-metal strip. When the resistance through the sending unit =
decreases, the nichrome wire heats up, causing the bi-metal strip to =
bend, which moves the indicator accordingly. If this is the case, then =
wiring polarity at the gauge simply doesn't matter...it will heat the =
bi-metal strip to the same degree no matter which direction the gauge is =
wired.

ON THE OTHER HAND, if it happens to be a magnetic induction-type guage =
(with a rotating wire coil), then wiring polarity at the gauge obviously =
matters. It would be possible to switch the wires at the gauge and get =
backwards results.

I'd have to take a closer look at my fuel guage to know for sure what =
type it is. I suspect that it's the bi-metal-strip-type gauge.

By the way, the reasons for using heated bi-metal strips in gauges =
include: considerably lower cost of manufacture, greater vibration/shock =
resistance, a slower response curve (so that sloshing fuel doesn't cause =
the needle to bounce around as much), and natural "dampening" of =
movement to prevent bouncing due to bumps in the road. A magnetic gauge =
can be inductively dampened, but not quite as effectively.

Alan
(Salt Lake City, Utah)

-----Original Message-----
From: Gordon.W.I. McMillan [SMTP:gwim2@student.open.ac.uk]
Sent: Wednesday, August 20, 1997 5:19 PM
To: alan_bowes@phast.com
Cc: MJW71683@aol.com; mil-veh@skylee.com
Subject: Re: RE: [MV] M-37 Gas Gauge

Sorry if this is a silly suggestion, but have you checked that the
battery and the guage are connected the right way round? Might be that
simple. Gordon 8-) (US MV fuel guages are 'approximate' anyway,
that's what jerry cans are for)

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