L
I,
DRIVE-CONTROL COMPONENTS
-
ABS
<AWD>
3-49
L
Piezo diffusion
resistor
Weight
Damping
oil
9FAOO50
Bridge circuit
Piezo diffusion
resistor
9FAOO44
/y(G)
-0.1
0
1.0
Accele-
-
Rate of
-
Decele-
ration
acceleration ration
9FAOO46
output
characteristics
Output voltage (V)
I
The semiconductor strain gauge type sensor, constructed as
shown at the left, consists of a weight mounted at the free
end of an N-type silicon leaf spring, and four P-type diffusion
layers made on the surface of the leaf spring to constitute
piezo diffusion resistors. The case is filled with a damping
oil to prevent breakdown that may be caused by resonance.
The piezo diffusion resistors, arranged as shown at the left,
complete a bridge circuit which constitutes a semiconductor
strain gauge.
When the sensor is placed under strain by acceleration, the
piezoelectric effect changes its electrical resistance, causing
the bridge circuit to go out of balance.
If a voltage is applied across the bridge circuit, the acceleration
can be measured by detecting the amount the bridge circuit
goes out of balance in terms of a change in the voltage.
The output characteristics vary as shown at the left in the
direction of acceleration with 2.5 V as 0 G.
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