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Flowmeter directory - Flow controllers terms Category: Electronics and Engineering > Industrial automation Date & country: 16/12/2007, UK Words: 713

T3 Carrier System
A North American digital communications link that is formed by multiplexing seven T2 systems and operates at 47.736 Mb/s. The European version is E3.

T2 Carrier System
A North American digital communications link that is formed by multiplexing three T1 systems and operates at 6.312 Mb/s. The European version is E2.

A-D Converter
(Also A/D or ADC) Short for analog-to-digital converter. Converts real-world analog signals into a digital format that can be processed by a computer.

Zero Voltage Switching
The making or breaking of circuit timed such that the transition occurs when the voltage wave form crosses zero voltage; typically only found in solid state switching devices.

Zero Suppression
The span of an indicator or chart recorder may be offset from zero (zero suppressed) such that neither limit of the span will be zero. For example, a temperature recorder which records a 100° span from 400° to 500° is said to have 400° zero suppression.

Zero Return
The difference in zero balance measured immediately before rated load application of specified duration and measured after removal of the load, and when the output has stabilized.

Zero Power Resistance
The resistance of a thermistor or RTD element with no power being dissipated.

Zero Point
The electrical zero point where zero millivolts would be displayed. Used in conjunction with the slope control to provide a narrower range calibration.

Zero Offset
1. The difference expressed in degrees between true zero and an indication given by a measuring instrument. 2. See Zero Suppression

Zero Balance
The output signal of the transducer with rated excitation and with no-load applied, usually expressed as a percent of rated output.

WWW
World Wide Web.

WYSIWYG
What You See Is What You Get.

Write
To record data in a storage device or on a data medium.

Working Standard
A standard of unit measurement calibrated from either a primary or secondary standard which is used to calibrate other devices or make comparison measurements.

Word
Number of bits treated as a single unit by the CPU. In an 8-bit machine, the word length is 8 bits; in a sixteen bit machine, it is 16 bits.

Window
In computer graphics, a defined area in a system not bounded by any limits; unlimited 'space' in graphics.

WHOIS
An Internet program which allows users to query a database of people and other Internet entities.

Wheatstone Bridge
A network of four resistances, an emf source, and a galvanometer connected such that when the four resistances are matched, the galvanometer will show a zero deflection or 'null' reading.

Wetted Parts
The diaphragm and pressure port material that comes in direct contact with the medium (gas, liquid).

Wet-Wet Differential
A differential pressure transducer or transmitter that has a metal diaphragm in each pressure port to permit fluid into both parts.

VSWR
Voltage Standing Wave Ratio.

Wet-Dry Differential
A differential pressure transducer or transmitter that uses a metal diaphragm at the wet port where fluids can be applied, and no diaphragm at the dry port. The dry port exposes the internal circuitry to the medium, so only clean dry gas can be applied to this port.

Voltmeter
An instrument used to measure voltage.

Volume Flow Rate
Calculated using the area of the full closed conduit and the average fluid velocity in the form, Q = V x A, to arrive at the total volume quantity of flow. Q = volumetric flowrate, V = average fluid velocity, and A = cross sectional area of the pipe.

Voltage
An electrical potential which can be measured in volts.

Viscosity
The inherent resistance of a substance to flow.

Volt
The (electrical) potential difference between two points in a circuit. The fundamental unit is derived as work per unit charge-(V = W/Q). One volt is the potential difference required to move one coulomb of charge between two points in a circuit while using one joule of energy.

Vibration Error
The maximum change in output of a transducer when a specific amplitude and range of frequencies are applied to a specific axis at room temperature.

Vibration Error Band
The error recorded in output of a transducer when subjected to a given set of amplitudes and frequencies.

VHF
Very High Frequency

UTC
Universal Time Code.

Velocity
The time rate of change of displacement; dx/dt.

UPS
Uninterruptible Power Supply.

Union
A form of pipe fitting where two extension pipes are joined at a separable coupling.

Undershoot
The difference in temperature between the temperature a process goes to, below the set point, after the cooling cycle is turned off and the set point temperature.

Unbalance Tolerance
The unbalance tolerance with respect to a radial plane (measuring plane or correction plane) is that amount of unbalance which is specified as the maximum below which the state of unbalance is considered acceptable.

Unbalance
That condition which exists in a rotor when vibratory force or motion is imparted to its bearings as a result of centrifugal forces.

Ultraviolet
That portion of the electromagnetic spectrum below blue light (380 nanometers).

UL
Underwriters Laboratories, Inc. An independent laboratory that establishes standards for commercial and industrial products.

Typical
Error is within plus or minus one standard deviation (±1%) of the nominal specified value, as computed from the total population.

Twisted Pair
Two insulated wires, usually made from copper, that are twisted in a regular, six turns per inch spiral pattern used to connect most telephones. Also used as a medium by several local area networks.

Turbulent Flow
When forces due to inertia are more significant than forces due to viscosity. This typically occurs with a Reynolds number in excess of 4000.

TTL-Compatible
For digital input circuits, a logic 1 is obtained for inputs of 2.0 to 5.5 V which can source 40 µA, and a logic 0 is obtained for inputs of 0 to 0.8 V which can sink 1.6 mA. For digital output signals, a logic 1 is represented by 2.4 to 5.5 V with a current source capability of at least 400 µA; and a logic 0 is represented by 0 to 0.6 V with a cur…

TTL Unit Load
A load with TTL voltage levels, which will draw 40 µA for a logic 1 and -1.6 mA for a logic 0.

TTL
Transistor-to-transistor logic. A form of solid state logic which uses only transistors to form the logic gates.

True RMS
The true root-mean-square value of an AC or AC-plus-DC signal, often used to determine power of a signal. For a perfect sine wave, the RMS value is 1.11072 times the rectified average value, which is utilized for low-cost metering. For significantly non-sinusoidal signals, a true RMS converter is required.

Triple Point (Water)
The thermodynamic state where all three phases, solid, liquid, and gas may all be present in equilibrium. The triple point of water is .01°C.

Triple Point
The temperature and pressure at which solid, liquid, and gas phases of a given substance are all present simultaneously in varying amounts.

Triac
A solid state switching device used to switch alternating current wave forms.

Transmitter
A transducer that has a 4-20 mA two wire output.

Transverse Sensitivity
Signal output as a result of acceleration perpendicular to the sensitive axis. Specified as a percentage of sensitive axis output for equivalent right angle acceleration or as a decimal fraction.

Transitional Flow
Flow between laminar and turbulent flow, usually between a pipe Reynolds number of 2000 and 4000.

Transient Vibration
A temporary vibration or movement of a mechanical system.

Transducer Vibration
Generally, any device which converts movement, either shock or steady state vibration, into an electrical signal proportional to the movement; a sensor.

Transducer
A device (or medium) that converts energy from one form to another. The term is generally applied to devices that take physical phenomenon (pressure, temperature, humidity, flow, etc.) and convert it to an electrical signal.

Token Ring
A LAN standard, also known as IEE 802.5, that connects a ring topology. Token Ring LANs operate at 4 Mb/s or 16 Mb/s.

TQM
Total Quality Management.

Token Passing
A protocol that gives a terminal permission to transmit on a Token Ring LAN. A unique bit pattern, called a token, circulates around the ring from terminal to terminal. The terminal that possesses the token has permission to transmit.

Thomson Effect
When current flows through a conductor within a thermal gradient, a reversible absorption or evolution of heat will occur in the conductor at the gradient boundaries.

Thermowell
A closed-end tube designed to protect temperature sensors from harsh environments, high pressure, and flows. They can be installed into a system by pipe thread or welded flange and are usually made of corrosion-resistant metal or ceramic material depending upon the application.

Thermopile
An arrangement of thermocouples in series such that alternate junctions are at the measuring temperature and the reference temperature. This arrangement amplifies the thermoelectric voltage. Thermopiles are usually used as infrared detectors in radiation pyrometry.

Thermocouple
The junction of two dissimilar metals which has a voltage output proportional to the difference in temperature between the hot junction and the lead wires (cold junction) (refer to Seebeck emf).

Thermistor
A temperature-sensing element composed of sintered semiconductor material which exhibits a large change in resistance proportional to a small change in temperature. Thermistors usually have negative temperature coefficients.

Thermal Zero Shift
An error due to changes in ambient temperature in which the zero pressure output shifts. Thus, the entire calibration curve moves in a parallel displacement.

Thermal Sensitivity Shift
The sensitivity shift due to changes of the ambient temperature from room temperature to the specified limits of the compensated temperature range.

Thermal Gradient
The distribution of a differential temperature through a body or across a surface.

Thermal Expansion
An increase in size due to an increase in temperature expressed in units of an increase in length or increase in size per degree, i.e. inches/inch/degree C.

Thermal Conductivity
The property of a material to conduct heat in the form of thermal energy.

Thermal emf
See Seebeck emf

Thermal Coefficient of Resistance
The change in resistance of a semiconductor per unit change in temperature over a specific range of temperature.

Terminal
An input/output device used to enter data into a computer and record the output.

Temperature, Operating
The range of temperature over which a transducer may be safely operated up to full scale without causing failure, but specificationsmay not be met.

Temperature, Compensated
The range of temperature over which a transducer can operate up to full scale and still meet all specifications.

Temperature Error
The maximum change in output, at any measurand value within the specified range, when the transducer temperature is changed from room temperature to specified temperature extremes.

Temperature Effect On Zero
The change in zero balance due to a change in ambient temperature. Usually expressed as +/- a percentage change in rated output per degree F change in ambient temperature over the compensated temperature range.

Temperature Effect On Span
The change in rated output due to a change in ambient temperature. Usually expressed as +/- a percentage change in rated output per degree F change in ambient temperature over the compensated temperature range.

Temperature Compensation
The utilization of supplementary devices, materials, or components within the bridge to minimize sources of error caused by changing temperature.

TEMPCO
Abbreviation for 'temperature coefficient': the error introduced by a change in temperature. Normally expressed in %/°C or ppm/°C.

TELNET
The Internet standard protocol for remote terminal connection service. Telnet allows a user at one site to interact with a remote timesharing system at another site as if the user's terminal was connected directly to the remote computer.

Telemetry
Transmission and collection of data obtained by sensing conditions in a realtime environment.

TDM
Time Division Multiplexing.

TCP
Transmission Control Protocol. A transport layer protocol for the Internet.

TCP-IP
Transmission Control Protocol/Internet Protocol. This is a common shorthand which refers to the suite of application and transport protocols which run over IP. These include FTP, Telnet, SMTP, and UDP (a transport layer protocol).

Syntax
The rules governing the structure of a language.

Suspension Effect
The source of error due to varied reference liquid junction potential depending upon whether the electrodes are immersed in the supernatant fluid or deeper in the sediment. Normally encountered with solutions containing resins or charged colloids.

Surge Current
A current of short duration that occurs when power is first applied to capacitive loads or temperature dependent resistive loads such as tungsten or molybdenum heaters-usually lasting no more than several cycles.

Supervisory Information
Signaling information used to connect, maintain, and disconnect a telephone circuit.

Super Heating
1. The heating of a liquid above its boiling temperature without the formation of the gaseous phase. 2. The heating of the gaseous phase considerably above the boiling-point temperature to improve the thermodynamic efficiency of a system.

Subscriber
A customer of a telephone company or other communications carrier.

Super Cooling
The cooling of a liquid below its freezing temperature without the formation of the solid phase.

Subcriber Line
Data transmission capacity over conventional twisted pair telephone lines. ADSL is a contender for a major piece of the 'information highway' pie and it promises to deliver telephone, television, and data services to your home over the existing telephone line.

Strain Gage
A measuring element for converting force, pressure, tension, etc., into an electrical signal.

Strain
The ratio of the change in length to the initial unstressed reference length.

Stop Bit
A signal following a character or block that prepares the receiving device to receive the next character or block.

Steady Flow
A flow rate in the measuring section of a flow line that does not vary significantly with time.

Static Unbalance
Static unbalance is that condition of unbalance for which the central principal axis is displayed only parallel to the shaft axis.

Static Router
A router whose routing table must be reprogrammed by the network manager every time there is a change made to the internet work.

Static Error Band
The error band applicable at room temperature.

Static Pressure
Pressure of a fluid whether in motion or at rest. It can be sensed in a small hole drilled perpendicular to and flush with the flow boundaries so as not to disturb the fluid in any way.

Static Calibration
A calibration recording pressure versus output at fixed points at room temperature.