Since microsensors do not transmit power, the scaling of force is not typically significant. As with
conventional-scale sensing, the qualities of interest are high resolution, absence of drift and hysteresis,
achieving a sufficient bandwidth, and immunity to extraneous effects not being measured.
Microsensors are typically based on either measurement of mechanical strain, measurement of
mechanical displacement, or on frequency measurement of a structural resonance.
The former two types are in essence analog measurements, while the latter is in essence a binary-type measurement, since the
sensed quantity is typically the frequency of vibration. Since the resonant-type sensors measure frequency
instead of amplitude, they are generally less susceptible to noise and thus typically provide a higher
resolution measurement. According to Guckel et al., resonant sensors provide as much as one hundred
times the resolution of analog sensors.
They are also, however, more complex and are typically more
difficult to fabricate.
The primary form of strain-based measurement is piezoresistive, while the primary means of displacement
measurement is capacitive. The resonant sensors require both a means of structural excitation as
well as a means of resonant frequency detection. Many combinations of transduction are utilized for
these purposes, including electrostatic excitation, capacitive detection, magnetic excitation and detection,
thermal excitation, and optical detection.
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