Transducers are often employed at the boundaries of automation, measurement, and control systems. Before choosing a transducer we have to ensure that the transducer is suitable for our need. These are factors which may influence the selection.
There are operating principles such as resistive, inductive, capacitive, piezoelectric, photo-voltaic, ionization etc.,
Transducer must be sensitive enough not to give an output, but to give an detectable output.
A transducer should have good resolution over it’s entire range of operation. We cannot choose a temperature sensing transducer that work in range 0-100 degree Celsius for a use in boiler where temperature is up to 1000 degree Celsius, that’s what it means.
High degree of accuracy is needed and small value of repeatablity.
Cross-sensitivity must taken into account while measuring mechanical quantity. Cross-sensitivity must reduced. Because when transducer subjected to measure variations in one plain, while actual quantity to be measured is in another plain.
A transducer must avoid error. For which a transducer should maintain expected input output relationship by it’s transfer function.
Transient & Frequency response:
Transducer should meet desired time domain specifications such as peak over shoot, raise time, setting time & small dynamic error, it should flat frequency response curve with higher cut-off frequency at high limit in-order to have a high value.
Transducer should have high input impedance and low output impedance to avoid loading effect.
Under specified environment conditions the transducer maintain input-output relationship and doesn’t breakdown. Transducer should be able to withstand temperature, pressure shock etc., when subjected to it, if it is application require so.
Insensitivity to unwanted signals:
Noise should be avoided in measuring, so that a good transducer should insensitive to unwanted signals. But high sensitive to desired signals.
Usage and ruggedness:
Ruggedness both of mechanical and electrical intensities of transducer VS it’s size and weight must be considered while selection.
Length and type of cable required must be considered.
Signal to noise ratio must be taken care.
Frequency response limitation must be taken to account.
Stability & reliability:
Should have high degree of stability during it’s operation & storage life. Reliability should be assure in case of failure of transducer in-ordered that functioning of the instrumentation system continues uninterrupted.
Apart from low static error transducers should have a low non linearity, high resolution, and a high degree of repeat-ability. Transducer selected should be free from temperature effect and load alignment effects. it should not need frequent calibration.