Sensors and Actuators - Fachbereich Physik der Universität ...

Quellen: www.sensedu.com, http://www.mhsg.de/Demo/Demo_Die_Erde/Data/Werkzeuge/Geophysik/M5-
Seismik/2Eigenschaften/Eigenschaften.htm, http://sensorik.upb.de/lehre/V3_DMS_New.pdf
Piezoresistive silicon pressure sensors employ resistors as sensing elements, diffused or
implanted into the surface region of a membrane made by anisotropic etching. A pressure
difference between the both sides of the membrane causes its deformation. Due to the
piezoresistive effect, the resistors follow the deformation with resistance changes; two
resistors increase and two decrease, resulting in a multiplied effect in the Wheatstonebridge
configuration. The resistance changes, ∆Ri, can be expressed as follows:
∆ R σ ∆l
= K ⋅ε with ε= =
R
E l
i
where K is the gauge factor (k-Faktor oder Dehnungsempflindlichkeit, dimensionslose Zahl
zwischen 1 und 200); σ ist die mechanische Spannung und ε die Dehnung (relative
Längenänderung ∆l/l); E is the Young's modulus (= modulus of elasticity, Elastizitätsmodul:
Maß für den Widerstand des Materials gegen elastische Verformung; je größer der
Elastizitätsmodul ist, desto geringer ist die Verformung der Materials) of the membrane.
Gauge factor is defined as the fractional change in resistance to the fractional change in
length (strain) along the axis of a strain gauge. It is a dimensionless quantity that applies to
the changes in the strain gauge as a whole. Typical gauge factors are close to 2.0. Gauge
factors for special strain gauges can be significantly larger or even negative.
A sensitivity factor is sometimes specified. The sensitivity factor equals the gauge factor
multiplied by a correction based on current measurement conditions. If the current
conditions are the same as those under which the gauge factor was specified, the
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