Basic instrumentation

Instrumentation is the process of measuring, calibrating, and controlling the physical variable such as pressure, flow, temperature etc using a instrument.


Calibration is the process of checking the accuracy and correctness of an instrument by comparing it with a standard instrument.


The degree of closeness to the true value.


The deviation of the true value from the desire value.


Transducer is defined as a device that receives energy from one system and transmits it to another often in a different form. Basically there are two types of transducers:

  1. Electrical Transducers
  2. Mechanical Transducers

An electrical transducer gives a sensing device by which the physical, mechanical, optical quantity to be measured, is transformed directly by a suitable mechanism into an electrical signal.

Electrical transducers can be classified into two ways:

  1. Active Transducers
  2. Passive Transducers

Active Transducers

Active transducers generate an electrical signal directly in response to the physical parameter and does not require external power source for its operation. Active transducers are self generating devices which operate under energy conversion principle and generate an equivalent output signal.

Passive Transducers

Passive transducers operate under energy controlling principle which makes it necessary to use an external electrical source with them. They depend up on the change in an electrical parameter (R, L, C).
E.g. Strain Gauge, Thermistors

Selecting a Transducers

Following should be considered while selecting a transducer:

  1. Operating range
  2. Sensitivity
  3. Environmental compatibility
  4. Accuracy

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