Instrumentation is defined as the science of measurement and control.
The term instrumentation may refer to something as simple as direct reading thermometers, gauges or may become part of a complex industrial control system in petrochemicals plants, oil & gas industry, manufacturing industry, vehicles and transportation etc. Instrumentation can be found in the household as well such as a smoke detector or a thermostat.
Instrumentation is a collective term for measuring instruments/devices used for indicating, measuring and recording physical quantities and process variable in any industry.The process variables used in industries are Level, Pressure, Temperature, Humidity, Flow, pH, Force, Speed etc.