2. Sensor
Sensor are devices which produce a proportional
output signal (mechanical, electrical, magnetic etc.,)
when exposed to a physical phenomenon (pressure,
temperature, displacement , force etc.,).
3. Transducer
Transducer are devices which converts an input of one
form of energy in to an output of another form of
energy.
4. Performance terminology
• Static characteristics
– Static characteristics of an instrument are the
parameters which are more or less constant or varying
very slowly with time.
• Dynamic characteristics
– Sensors and actuators respond to inputs that change
with time. Dynamic characteristics of an instrument are
the parameters which are varying with time.
5. Static characteristics
Range –Every sensor is designed to work over a
specified range. e.g.: a thermocouple may have a range
of -100 to 1160°C
Span : maximum value of input – minimum value of
input.
Error : measured value – true input value
Accuracy : is inversely proportional to error.
Sensitivity: it is defined as the change in output per
change in input
6. Static characteristics
Hysteresis: it is defined as the maximum difference in
output for a given input when this value is approached
from the opposite direction.
Linearity: it is refer to the output that is directly
proportional to input over its entire range.
7. Static characteristics
• Repeatability: it is defined as the ability of the sensor
to give same output reading when the same input value
is applied repeatedly under the same operating
conditions.
• Reproducibility: it is defined as the degree of closeness
among the repeated measurements of the output for
the same value of input under the same operating
conditions at different times.
8. Static characteristics
Stability : it means the ability of the sensor to indicate
the same output over a period of time for a constant
input.
Resolution: it is defined as the smallest change that
can be detected by a sensor
