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.
The Automation Group (TAG) offers a full range of field and shop services to test, calibrate, and repair all types of control devices. Protective relays can be tested to assure their proper performance during a power system disturbance. Our technicians can calibrate or repair equipment as required to return the device to its original performance specifications. In addition, meters, transducers and many types of industrial electronics can be tested calibrated, and repaired in the field or in our shop.
Measurement
Instrumentation can be used to measure certain field parameters (physical values). These measured values include:
- pressure, either differential or static
- flow
- temperature
- level
- density
- viscosity
- radiation
- current
- voltage
- inductance
- capacitance
- frequency
- resistivity
- conductivity
- chemical composition
- chemical properties
- various physical properties
- force applied by a liquid
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"The City of Depoe Bay has worked with the Automation Group throughout the years. As everyone knows who has been through a big wastewater plant improvement project, you have a few bugs to workout during start up and operations. Though the Automation Group did not install the controls and instrumentation, they have been a continuous help to fix problems and brainstorm to make the City's plant run smoother, more control of process and staying within budget restraints. The City has now hired them to completely replace the control system and re-program the PLC at the city's water plant. I have found them easy to work with, and if we have a emergency they will make sure we are contacted and set up a service call."
Terry Owings
City Superintendent
City of Depoe Bay, OR
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