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Measuring of Absolute and Differential
Pressure.
Pressure sensors can register a
membrane flexion produced by
pressure at placing on the membrane
a strain bridge. Pressure sensors
modify their electrical resistance
because of the piezoresistive
effect in the case of flexion,
pressure or traction. Some years
ago, pressure sensors were made of
constantana or
platinum-iridium layers. Nowadays,
silicon resistances are commonly
used. An advantage of using
silicon resistances is that the
manufacturing process will be
cheaper sensitivity higher
than 10 factor. On the other hand,
there is a disadvantage related to
the higher higher temperature
coefficient. With the differential
pressure sensor the p1 pressure is
determined at one side of the
membrane while p2 is in the other
side. To measure pressure with the
absolute pressure sensor, we place
four connected strain bands similar
to a resistance bridge. The way they
are connected allows to change their
places in the bridge laterals. By
means of this process, as it is
shown in images 2 and 3, it is
compensated an output signal in the
same way that resistances absolute
values and coefficient temperatures.
Because of the few changes of the ∆R
resistance, the output signal will
remain lower. Depending on the
sensor, the maximum pressure
will be between 25 and 250 mV with a
voltage of Uref = 5 V. The relative
change of the resistance is from 0,5
y 5 %. |
