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Instrumentation is an electrical or pneumatic device
placed in the field to provide measurement and/or
control capabilities for the system.
The simplest measurement instrumentation device is a
thermistor. A thermistor is very similar to a
typical resistor, except that it greatly varies its
resistance depending on its temperature. Therefore
this device can easily be used for measurement of
temperature in the field. Other
temperature-sensitive devices include RTDs, which
also change resistance depending on temperature, and
thermocouples, which produce a varying voltage when
subjected to heat.
Control instrumentation includes devices such as
solenoids, Electrically Operated Valves, breakers,
relays, etc. These devices are able to change a
field parameter, and provide remote control
capabilities.
Transmitters are devices which produce an analog
signal, usually in the form of a 4-20 mA electrical
current signal, although many other options are
possible using voltage, frequency, or pressure. This
signal can be used to directly control other
instruments, or sent to a PLC, DCS, SCADA system or
other type of computerized controller, where it can
be interpreted into readable values, or used to
control other devices and processes in the system.
Instrumentation plays a significant role in both
gathering information from the field and changing
the field parameters, and as such are a key part of
control loops. |
