Biomedical Engineering Reference
In-Depth Information
Resolution
Resolution is defined as the smallest change that can be detected by a sensor de-
vice. This fluctuation is a measure of the sensor resolution and is given in the
specification as the minimum change that is detectable in the range.
Response
Thetimetakenbyasensortoapproachits true output when subjected to step
input is sometimes referred to as its response time. It is more usual, however,
to quote a sensor as having a flat response between specified limits of frequency.
This is known as the frequency response, and it indicates if the sensor is subjected
to steps, for example, similar to a sinus-oscillating input of constant amplitude, the
output will faithfully reproduce a signal proportional to the input. The response
function can be further related to the system bandwidth and transfer function.
Linearity
The most convenient sensor to prefer and choose in a system would of course be
the one with an acceptable linear transfer function. The ideal function provides
an output that is directly proportional to input over its entire range, so that the
slope of a graph of output versus input describes a straight line. However, the
deviation, is the actual transfer function compared to the ideal function defines
the sensor linearity (or more correct the non-linearity).
Hysteresis
Hysteresis is the behaviour and sensor inability to return to the same output value
when applying the same input parameter. Hysterisis refers to the characteristic
that a sensor has, in being unable to repeat faithfully a measurement cycle, in the
opposite direction of operation, compared to the data that have been recorded in
one direction, as seen in Fig. 4.4.
Figure 4.4.
The hysteresis function of a measurement cycle.
Search WWH ::
Custom Search