Monitoring and Control Instruments

About the instruments used for monitoring and controlling

An important distinction between different instruments is whether they are suitable only for monitoring functions or whether their output is in a form that can be directly included as part of an automatic control system. Instruments which only give an audio or visual indication of the magnitude of the physical quantity measured, such as a liquid-in-glass thermometer, are only suitable for monitoring purposes. This class normally includes all null-type instruments and most passive transducers.


For an instrument to be suitable for inclusion in an automatic control system, its output must be in a suitable form for direct input to the controller. Usually, this means that an instrument with an electrical output is required, although other forms of output such as optical or pneumatic signals are used in some systems.


More Instrument Classification

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