Instrumentation & Controls
Instrumentation is the ability to control a process by measuring the value or the parameters set for the process. This can include control, flow, level, pressure and temperature.
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Instrumentation & Controls standards
API Standards
- API RP 521 - Guides for Pressure Relief and Depression Systems
- API RP 550 - Manual on Instrumentation of Refinery Instruments and Control Systems
- API RP 551 - Process Measurement Instrumentation
- API RP 552 - Transmission Systems
- API RP 554 - Process Instruments and Controls
- API RP 598 - Valve Inspection and Testing
ISA Standards
- ISA 5 - Documentation of Measurement, and Control Instruments and Systems
- ISA 5.1 - Instrimentation Symbols and Identification
- ISA 12 - Electrical Equipment for Hazardous Locations
- ISA 18 - Instrument Signals and Alarms
- ISA 37 - Instrument Transducers
- ISA 50 - Signal Compatibility of Electrical Instruments
- ISA 60 - Control Centers
- ISA 75 - Control Valve Standards
- ISA 82 - Electrical and Electronic Instrumentation
- ISA 90 - Instrumentation and Computer Grounding
- ISA 91 - Criticality Ranking for Instrumentation
- ISA 99 - Industrial Automation and Control Systems Security
- ISA 100 - Wireless Systems for Automation
- ISA 101 - Human-Machine Interface
- ISA 104 - Device Integration
- ISA 106 - Process Automation for Continuous Process Operations
- ISA 107 - Advanced Measurement Techniques for Gas Turbine Engines
- ISA 108 - Intelligent Device Management
Instrumentation & Controls Glossary
A
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- Analog - A continuous electronic variable signal caring information.
- Analog Output - A signal coming from a PLC into an instrument or controller.
- Automatic Well Test - Specified as on instrument bubbles on Piping and Instrumentation Diagram.
B
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C
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- Cache - High-speed processor memory that buffers commonly used instructions or data to increase processing throughput.
- Capacitance - The ability to hold an electric charge.
- Car Seal - Specified on instrument bubbles on Piping and Instrumentation Diagram.
- Current - The rate of flow of electricity in a circuit, measured in amperes. Amp is a unit of current. One ampere (amp) is the current flowing through one ohm of resistance at one volt potential.
D
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- Differential Pressure Flowmeter - There are many different types of instruments for measuring pressure. The functions of these instruments are to monitor and control pressure in a process stream.
- Differential Set Pressure - The pressure difference between the set pressure and constant back pressure.
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Discrete Input - Relative to the device that reads either a TRUE or a FALSE, 1 or 0, or ON of OFF as an input signal.
E
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- Electric Current - The rate of flow of electricity in a circuit, measured in amperes.
- External Trigger - A voltage pulse from an external source that trig- gers an event such as A/D conversion.
F
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- Flow Quality Indicating Transmitter - , abbreviated as FQIT, is an instrument that is used for measuring the amount of a liquid and a gas in two pase flow.
- Flow Switch - Provides a discrete input to the PLC. The flow switch is typically used as a method of control in tanks, vessels, pumps and other types of process equipment.
- Flowmeter - An instrument used to measure the flow rate of gasses and liquids.
G
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- Gain Accuracy - A measure of deviation of the gain of an amplifier from the ideal gain.
- Gauge Factor - A measure of the ratio of the relative change of resistance to the relative change in length of a piezoresistive strain gage.
- Grounded Junction - A form of construction of a thermocouple probe where the hot or measuring junction is in electrical contact with the sheath material so that the sheath and thermocouple will have the same electrical potential.
H
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- Half Bridge - Two active elements or strain gages.
I
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- Input Impedance - The resistance measured across the excitation terminals of a transducer.
- Insulation Resistance - The resistance measured between two insulated points on a transducer when a specific DC voltage is applied at room temperature.
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Integral Control - A control action that eliminates the steady-state offset inherent in proportional control.
- Interface - The means by which two systems or devices are connected and interact with each other.
- Interrupt - A computer signal indicating that the CPU should suspend its current task to service a designated activ- ity.
J
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- Junction - The point in a thermocouple where the two dissimilar metals are joined.
K
L
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- Loop Resistance - The total resistance of a thermocouple circuit caused by the resistance of the thermocouple wire. Usually used in reference to analog pyrometers which have typical loop resistance requirements of 10 ohms.
M
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- Manual Reset - The adjustment on a proportioning controller which shifts the proportioning band in relationship to the set point to eliminate droop or offset errors.
- Maximun Operating Temperature - The maximum temperature at which an instrument or sensor can be safely operated.
- Maximum Power Rating - The maximum power in watts that a device can safely handle.
- Meter - A device that provides a measurement for the flow change in a gas or liquid.
- Motherboard - The pc board of a computer that contains the bus lines and edge connectors to accommodate other boards in the system. In a microcomputer, the motherboard contains the microprocessor and connectors for expansion boards.
- Mounting Error - The error resultant from installing the transducer, both electrical and mechanical.
- Multiplex - A technique which allows different input or output signals to use the same lines at different times, controlled by an external signal.
N
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- Noise - An undesirable electrical signal. Noise comes from external sources such as the AC power line, motors, generators, transformers, fluorescent lights, solder- ing irons, CRT displays, computers, electrical storms, welders, radio transmitters, and internal sources such as semiconductors, resistors, and capacitors.
O
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- Operating System - A collection of programs that controls the overall operation of a computer and performs such tasks as assigning places in memory to programs and data, processing interrupts, scheduling jobs and controlling the overall input/output of the system.
- Orifice Discharge Coefficient - The ratio of actual discharge to the theoretical discharge.
- Orifice Flange - Meters the volumetric flow rate of liquids and gasses through a pipe. Two orifice flanges are called an orifice flange union.
- Orifice Flow Rate - The amount of fluid that flows in a given time.
- Orifice Plate - Measures the flow of a liquid or gas by the difference in pressure from the upstream to the downstream.
- Output - The electrical signal which is produced by an applied input to the transducer.
- Output Impedance - The resistance as measured on the output terminals of a pressure transducer.
P
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- Position Switch - Provides a discrete input to the PLC. The position switch is used to confirm the position of a critical component in the process, often a valve.
- Pressure Differential Transmitter - Measures the difference between a high pressure input and a low pressure input. This can be used to measure process properties such as flow, density, level, viscosity and temperature.
- Pressure Indicating Transmitter -, abbreviated as PT and PIT, is an instrument for measuring, controlling and indicating positive, negative or differential pressures of different fluids.
- Pressure Indicator - It is a field instrument that requires little to no maintenance.
- Pressure Switch - A discrete input to the PLC. The pressure switch is typically used as a method of control in tanks, vessels and over all process control.
Q
R
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Repeatability - The ability of the switch to actuate repeatedly at the desired set point within sensor tolerance.
- Reset Point - After the pressure has reached set point and operated the electrical switch, it must return to the reset point before the electrical switch returns to its original position.
- Resistance Temperature Detectors - A sensor used to measure temperature by correlating the resistance of the element with temperature.
S
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- Shunt - A calibrated low resistance connected in parallel with the input terminals of an ammeter in order to enable measurement of higher currents. It can be internal or external.
T
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- Temperature Controller - An instrument designed to minimize operator input or involvement. A temperature controller has an input that is connected to a temperature source such as an RTD or other type of temperature element.
- Temperature Differential Switch - Contains the same functionality of a temperature switch with the exception that it is looking for the difference of temperature rather than a single input.
- Temperature Recorder - A device that records the temperature of a process. This could be a data logger or a temperature transmitter capable of storing data.
- Temperature Switch - Provides alarm, shutdown and control for many types of processes. Switch that activates when a certain temperature condition is met.
- Termination - A load connected to the end of a transmission line. To avoid signal reflections, it must match the characteristic impedance of the line.
- Thermopile - A number of thermocouples connected in series, arranged so that alternate junctions are the referenced temperature and at the measured temperature to increase the output for a given temperature difference between the measuring and reference junctions.
- Thermowell - Used in temperature measurement and provide isolation from the temperature sensor and the process fluid.
U
V
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- Variable Data - Numerical information that can be changed during application operation. It includes timer and counter accumulated values, thumbwheel settings, and arithmetic results.
- Volt - A unit of electrical pressure. One volt is the amount of pressure that will cause one ampere of current in one ohm of resistance.
W
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- Watt Density - The watts emanating from each square inch of heated surface area of a heater.
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Tags: Glossaries