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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• Background Noise  -  Interfering signals that can cause disturbance affecting a signal that may distort the intended signal.

• Backplane  -  A group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus.  It is used as a backbone to connect several printed circuit boards together to make up a complete computer system.

• Batch process  -  Any process on which operations are carried out on a limited number of articles, as opposed to continuous process.

• Bus  -  The group of conductors that interconnect individual circuitry in a computer. Typically, a bus is the expansion vehicle to which I/O or other devices are connected. Examples of PC buses are the ISA and PCI buses

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.

• Carrier Frequency  -  The transmission of a fixed frequency that has been changed or modified to carry data or information.  The frequency is usually measured in Hertz (cycles per second).

• Channel List  -  A variable length list of channels and their associated gains specifying which analog input channels to convert to digital values.  In continuous A/D acquisition mode, the list wraps around to the first channel after it reaches the end.  The channels need not be in any particular order.

• 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.

• Current Drive Capability  -  The amount of current a digital or analog output channel is capable of sourcing or sinking while still operating within voltage range specifications.

D         

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• Data Length  -  Indicates the set data format.

• Data Recorder  -  Another name for a data logger, though data recorders are typically higher performance and offer higher sample rates than a typical data logger.

• 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.

• 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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• Ethernet  -  A family of computer networking technologies for local area networks (LANs) first introduced in 1980.  Systems that use Ethernet for communications divide a stream of data into individual packets called frames.  Each frame contains source and destination addresses and error-checking data so that damaged data can be detected and re-transmitted.

• 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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• Filter  -  A device that allows certain parts of a signal to pass through while blocking others.  In data acquisition systems, the most common type of filter used is a low pass, anti-aliasing filter.

• Firewall  -  A device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass.
  

• 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.

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

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 rea -

• Orifice Center of Head  -

• 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 Gravitational Constant  -

• Orifice Head Loss  -

• Orifice Plate  -  Measures the flow of a liquid or gas by the difference in pressure from the upstream to the downstream.

• Orifice Pressure Loss  -

• Orifices and Nozzles on a Horizontal Plane  -

• Orifices and Nozzles on a Vertical Plane  -

• 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.

• Velocity Flowmeter  -

• 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.

• Voltage – The value of electrical potential difference across a conductor expressed in volts.
  

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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