Instrumentation
An instrument is a device that measures or manipulates process physical variables such as flow, temperature, level, or pressure etc. Instruments include many varied contrivances which can be as simple as valves and transmitters, and as complex as analyzers. Instruments often comprise control systems of varied processes. The control of processes is one of the main branches of applied instrumentation.
Control instrumentation includes devices such as solenoids, valves, circuit breakers, and relays. These devices are able to change a field parameter, and provide remote or automated 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 using voltage, frequency, or pressure are possible.
This signal can be used to control other instruments directly, or it can be sent to a PLC, DCS, SCADA system, or other type of computerized controller, where it can be interpreted into readable values and 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.
Measurement
Instrumentation can be used to measure certain field parameters (physical values):
These measured values may include:
pressure, either differential or static, flow, temperature, level, density, viscosity, radiation, process instrumentation etc … list goes on.
Control
In addition to measuring field parameters, instrumentation is also responsible for providing the ability to modify some field parameters.
Instrumentation Engineering
Instrumentation engineering is the engineering specialization focused on the principle and operation of measuring instruments which are used in design and configuration of automated systems in electrical, pneumatic domains etc.
They typically work for industries with automated processes, such as chemical or manufacturing plants, with the goal of improving system productivity, reliability, safety, optimization and stability.
To control the parameters in a process or in a particular system, devices such as microprocessors, microcontrollers or PLCs are used, but their ultimate aim is to control the parameters of a system.