Peter Zaborski writes: <peterz@merak.com>
>> From: Andrew Mace [mailto:amace@unix2.nysed.gov]
>> Sent: Friday, December 18, 1998 11:55 AM
>>
>> On Fri, 18 Dec 1998, Peter Zaborski wrote:
>>
>> The "stabilized" gauges (fuel and temp.) don't do that, taking a bit o=
f
>time
>> to reach their measured reading. They don't NEED to, as neither runnin=
g
>> out of gas or loss of coolant is as likely to cause quick, irreversibl=
e
>> damage
>>
>Yes I agree. But I thought another reason for the use of the voltage
>stabilizer was to account for changes in the voltage supplied to the gau=
ge
>as various events occur during a drive (temp changes, accessories turned=
on
>and off, etc). Would an unstabilized electric gauge not be susceptible t=
o
>these changes?
>- --- Peter Zaborski CF58310UO ---
Lets not confuse cause and effect here. The use of a voltage stabilizer
does not cause a particular gauge to be more or less responsive. Rather
the type of gauge used determines whether or not it can be used with a
voltage stabilizer.
There are two types of gauges typically used in automobiles.
The first type is the D'Arsanval (sp?) This type uses magnetic
force to oppose a spring. The magnetic force is a function of
the current which is controlled by the sending unit (either
temperature, fuel level, oil pressure, etc). This type of
meter responds very fast and you can see subsecond deviations
in the reading.
The second type is the heated wire gauge. This type uses the
current (which is a function of the sending unit) to heat a
bimetal spring which causes needle deflection. The response time
of this type of meter is obviously much slower than the other.
A third part of this equation is the voltage stabilizer. Although
one can use an integrated circuit voltage regulator for this
function, there were no such things back in the glory days of the
LBC. Instead, there was a voltage stabilizer that had a heated wire
element inside (much like the one in the gauges) which would heat
up and open the contacts. Then it would cool downand the contacts
would close again. The contacts would open and close and the volage
to the meters will switch from battery voltage to zero in such a
manner that the average voltage is a fixed amount (8 volts or so).
This is an early version of a switch-mode-regulator using
pulse-width-modulation to regulate the output voltage over a range
of input voltages. The contacts open and close at a rate of once
or twice a second.
The up shot of this is that if you use a magnetic type meter on
the voltage stabilizer you will see the meter respond each time the
contacts in the stabilizer open and close. When they close the
meter will jump up to a reading that is a function of the sending
unit and the system voltage. When the contacts open the meter
will drop to zero. In otherwords the gauge would be virtually
unusable and distracting so it would be best to hook it up directly
to the 12 volt supply. Yes you will get readings that vary with
the battery voltage but not all that much. And, if you insist,
you can use a modern integrated circuit voltage regulator to
stabilize the voltage for this meter for stabilized readings.
Anyway, you always have the oil pressure failure warning light!
Dave Massey
57 TR3
71 TR6
80 TR8
P.S. Wake up now, I'm finished with my epistle.
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