Stewart Warner Performance Catalog - Auto Electric Service, Inc.

Technical Information
Electrical Gauges Mechanical Gauges
HOW THEY WORK:
At the heart of every Stewart Warner Electrical Gauge is
our high-performance, patented air-core movement—the
gauge’s motor. Looking inside the motor reveals two coils
(“A” and “B”) comprised of copper wire wrapped around
the front bobbin, and a rear bobbin assembly that contains
a mag-netized armature assembly (magnet & shaft),
surrounded by dampening fluid which acts to minimize
pointer flutter and ensure smooth response. The bobbin
assembly
is packaged
in a
metal isolation
can
that supports
the
gauge’s
dial (and
light pipe
where appropriate),
and the can is mounted inside a housing (case).
The armature assembly freely rotates within the coils, aligning
with the varying magnetic fields produced by the
amount of current flowing through the coils. (Current variance
is triggered by signals provided by the sender.) The
pointer—attached to the shaft on the armature assembly—
once calibrated, will provide a directional indication regarding
the amount of pressure, temperature, appropriate level
of fuel, or voltage being measured.
Senders that drive Stewart Warner Performance Electric
Gauges are based on variable resistance technology. The
three basic variable resistance senders are temperature,
pressure and fuel level. Each sender possesses a different
rate of resistance change, or “MATCH”, for the specific
gauge’s electrical design. The sender’s resistance change
results in current changes within the sender-gauge circuit.
These changes cause an increase or decrease in the gauge’s
magnetic field. The variance in the magnetic field causes
pointer movement.
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HOW THEY WORK:
Stewart Warner Performance Mechanical Gauges include
integral “Bourdon” tubes which have one free-floating end
that is linked to a gear and
shaft assembly, with pressure
pulsation and vibration
dampening to reduce
pointer fluctuations. The
Bourdon tube can be finetuned
by varying its
strength and stiffness. It
works by being deflected
(moved) by the pressure of
the liquid/gas that is being
measured, and it then
moves the gear and shaft
assembly which, in turn,
moves the pointer to produce
an accurate levelreading
on your dial.
Mechanical pressure gauges have a port on the back to
make a direct connection, whether through hose or tubing,
with the fluid or gas being measured. Mechanical temperature
gauges have a sealed capillary tube and bulb assembly,
which is filled with temperature sensitive liquid.
This liquid produces a proportional vapor pressure when
it is exposed to temperature variation. The vapor pressure
is the acting force on the Bourdon tube and is calibrated
to provide accurate pointer movement in relation to the
temperature.
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