T&T: Westerbeke Genny question

[2elnav at netbistro.com]

Some  automotive gauges uses a thermal bimetallic design. A small heating 
coil is wrapped around the bi-mettalic element  that moves the needle.
Although it seems wasteful it does have benefits.  Slow response; so the 
needle does not flicker.  Its also cheaper to manufacture  compared to a 
moving coil design. And its rugged.  It stands up better to mounting 
directly on a genset frame.
These meters will run warm or perhaps 'hot'  dependign on the observer's 
perception.
A genset manufacturer might well chose such a design as a low cost solution 
to installing  meters directly on a product while controlling cost.

Arild


----- Original Message ----- 
From: "Dennis OConnor" <ad4hk2004 at yahoo.com>
>A voltmeter works by measuring the current through a resistor, which 
>connected
> between the plus and minus leads...  The more voltage, the more current, 
> and
> vice versa... Since the value of the resistor is known the ammeter face 
> can be
> marked to read each given current flow as a voltage number...  All 
> resistors
> work by converting current into heat - just like your electrical space 
> heater,
> etc......
>
> I am surprised that your voltmeter is generating palpable heat...  Since 
> most
> meters are in the 50microamp to 1 milliamp range, the currents drawn 
> through
> the resistor are small and therefore the heat generated is small.. 
> However,
> if the space around the meter is dead air with no ventilation, then over 
> time
> the case will heat up...Assuming that the case of the meter is not hot - 
> as in
> burns your fingers - all is probably well...
>
> denny / k8do
>
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