Flow meter Glossary
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ac: Alternating current; an electric current that reverses its direction at regularly recurring intervals.
Accuracy: The closeness of an indication or reading of a measurement device to the actual value of the quantity being measured. Usually expressed as ± percent of full scale output or reading.
Acoustics: The degree of sound. The nature, cause, and phenomena of the vibrations of elastic bodies; which vibrations create compressional waves or wave fronts which are transmitted through various media, such as air, water, wood, steel, etc.
Adapter: A mechanism or device for attaching non-mating parts.
ADC: Analog-to-Digital Converter: an electronic device which converts analog signals to an equivalent digital form, in either a binary code or a binary-coded-decimal code. When used for dynamic waveforms, the sampling rate must be high to prevent aliasing errors from occurring.
Ambient Compensation: The design of an instrument such that changes in ambient temperature do not affect the readings of the instrument.
Ambient Conditions: The conditions around the transducer (pressure, temperature, etc.).
Ambient Pressure: Pressure of the air surrounding a transducer.
Ambient Temperature: The average or mean temperature of the surrounding air which comes in contact with the equipment and instruments under test.
Ampere (amp): A unit used to define the rate of flow of electricity (current) in a circuit; units are one coulomb (6.28 x 1018 electronics) per second.
Amplitude: A measurement of the distance from the highest to the lowest excursion of motion, as in the case of mechanical body in oscillation or the peak-to-peak swing of an electrical waveform.
Analog Output: A voltage or current signal that is a continuous function of the measured parameter.
Analog-to-Digital Converter (A/D or ADC): A device or circuit that outputs a binary number corresponding to an analog signal level at the input.
ATC: Automatic temperature compensation.
Background Noise: The total noise floor from all sources of interference in a measurement system, independent of the presence of a data signal.
Bandwidth: A symmetrical region around the set point in which proportional control occurs.
Baud: A unit of data transmission speed equal to the number of bits (or signal events) per second; 300 baud = 300 bits per second.
Bearing: A part which supports a journal and in which a journal revolves.
Beta Ratio: The ratio of the diameter of a pipeline constriction to the unconstricted pipe diameter.
BNC: A quick disconnect electrical connector used to inter-connect and/or terminate coaxial cables.
BTU: British thermal units. The quantity of thermal energy required to raise one pound of water at its maximum density, 1 degree F. One BTU is equivalent to .293 watt hours, or 252 calories. One kilowatt hour is equivalent to 3412 BTU.
Bus: Parallel lines used to transfer signals between devices or components. Computers are often described by their bus structure (i.e., S-100, IBM PC).
Calibration: The process of adjusting an instrument so that its reading can be correlated to the actual value being measured.
Cavitation: The boiling of a liquid caused by a decrease in pressure rather than an increase in temperature.
CE approval: CE marking is a declaration by the manufacturer that the product meets all the appropriate provisions of the relevant legislation implementing certain European Directives. The initials "CE" do not stand for any specific words but are a declaration by the manufacturer that his product meets the requirements of the applicable European Directive(s). Portaflow 330, 220A, 220B models manufactured in accordance with the following Directives and Standards: Directive 2004/108/EC, Directive 2006/95/EC. BS EN 61010-1:2001, BS EN61326-1:2006, BS EN613626-2:2006.
Centre of Gravity (Mass Centre): The centre of gravity of a body is that point in the body through which passes the resultant of weights of its component particles for all orientations of the body with respect to a uniform gravitational field.
CFM: The volumetric flow rate of a liquid or gas in cubic feet per minute.
Closeness of Control: Total temperature variation from a desired set point of system. Expressed as "closeness of control" is ±2°C or a system bandwidth with 4°C, also referred to as amplitude of deviation.
Colour Code: The ANSI established colour code for thermocouple wires in the negative lead is always red. Colour Code for base metal thermocouples is yellow for Type K, black for Type J, purple for Type E and blue for Type T.
Communication: Transmission and reception of data among data processing equipment and related peripherals.
Compensated Connector: A connector made of thermocouple alloys used to connect thermocouple probes and wires.
Compensation: An addition of specific materials or devices to counteract a known error.
Confidence Level: The range (with a specified value of uncertainty, usually expressed in percent) within which the true value of a measured quantity exists.
Connection Head: An enclosure attached to the end of a thermocouple which can be cast iron, aluminium or plastic within which the electrical connections are made.
Convection: 1. The circulatory motion that occurs in a fluid at a non-uniform temperature owing to the variation of its density and the action of gravity. 2. The transfer of heat by this automatic circulation of fluid.
CPS: Cycles per second; the rate or number of periodic events in one second, expressed in Hertz (Hz).
Critical Damping: Critical damping is the smallest amount of damping at which a given system is able to respond to a step function without overshoot.
Critical Speed: The rotational speed of the rotor or rotating element at which resonance occurs in the system.
Damping: The reduction of vibratory movement through dissipation of energy. Types include viscous, coulomb, and solid.
dB (Decibel): 20 times the log to the base 10 of the ratio of two voltages. Every 20 dBs correspond to a voltage ratio of 10, every 10 dBs to a voltage ratio of 3.162. For instance, a CMR of 120 dB provides voltage noise rejection of 1,000,000/1. An NMR of 70 dB provides voltage noise rejection of 3,162/1.
DC: Direct current; an electric current flowing in one direction only and substantially constant in value.
Dead Volume: The volume of the pressure port of a transducer at room temperature and ambient barometric pressure.
Default: The value(s) or option(s) that are assumed during operation when not specified.
Degree: An incremental value in the temperature scale, i.e., there are 100 degrees between the ice point and the boiling point of water in the Celsius scale and 180°F between the same two points in the Fahrenheit scale.
Density: Mass per unit of volume of a substance. I.E.: grams/cu.cm. or pounds/cu.ft.
Deviation: The difference between the value of the controlled variable and the value at which it is being controlled.
Differential: For an on/off controller, it refers to the temperature difference between the temperature at which the controller turns heat off and the temperature at which the heat is turned back on. It is expressed in degrees.
Digital Output: An output signal which represents the size of an input in the form of a series of discrete quantities.
Digital-to-Analog Converter (D/A or DAC): A device or circuit to convert a digital value to an analog signal level.
DIN (Deutsche Industrial Norm): A set of German standards recognized throughout the world. The 1/8 DIN standard for panel meters specifies an outer bezel dimension of 96 x 48 mm and a panel cutout of 92 x 45 mm.
Doppler Technology: An acoustic pulse is reflected back to the sensor from particles or gases in the flowing liquid. The flow rate of any fluid can be measured as long as it contains air bubbles or solids. It is ideal for wastewater, slurries, sludge and most chemicals, acids, caustics and lubrication fluids.
Drift: A change of a reading or a set point value over long periods due to several factors including change in ambient temperature, time, and line voltage.
Duplex: Pertaining to simultaneous two-way independent data communication transmission in both direction. Same as "full duplex".
Echo: To reflect received data to the sender. For example, keys depressed on a keyboard are usually echoed as characters displayed on the screen.
Electrical Interference: Electrical noise induced upon the signal wires that obscures the wanted information signal.
EMI: Electromagnetic interference.
Emissivity: The ratio of energy emitted by an object to the energy emitted by a blackbody at the same temperature. The emissivity of an object depends upon its material and surface texture; a polished metal surface can have an emissivity around 0.2 and a piece of wood can have an emissivity around 0.95.
End Point (Potentiometric): The apparent equivalence point of a titration at which a relatively large potential change is observed.
Environmental Conditions: All conditions in which a transducer may be exposed during shipping, storage, handling, and operation.
Error: The difference between the value indicated by the transducer and the true value of the measurand being sensed.
Explosion-proof Enclosure: An enclosure that can withstand an explosion of gases within it and prevent the explosion of gases surrounding it due to sparks, flashes or the explosion of the container itself, and maintain an external temperature which will not ignite the surrounding gases.
Exposed Junction: A form of construction of a thermocouple probe where the hot or measuring junction protrudes beyond the sheath material so as to be fully exposed to the medium being measured. This form of construction usually gives the fastest response time.
Fahrenheit: A temperature scale defined by 32° at the ice point and 212° at the boiling point of water at sea level.
Ferrule: A compressible tubular fitting that is compressed onto a probe inside a compression fitting to form a gas-tight seal.
Field Balancing Equipment: An assembly of measuring instruments for performing balancing operations on assembled machinery which is not mounted in a balancing machine.
Field of View: A volume in space defined by an angular cone extending from the focal plane of an instrument.
File: A set of related records or data treated as a unit.
Flow Rate: Actual speed or velocity of fluid movement.
Flow: Travel of liquids in response to a force (i.e. pressure or gravity).
FPM: Flow velocity in feet per minute.
FPS: Flow velocity in feet per second.
Freezing Point: The temperature at which the substance goes from the liquid phase to the solid phase.
Frequency Output: An output in the form of frequency which varies as a function of the applied input.
Frequency, Natural: The frequency of free (not forced) oscillations of the sensing element of a fully assembled transducer.
Frequency: The number of cycles over a specified time period over which an event occurs. The reciprocal is called the period.
Full Scale Output: The algebraic difference between the minimum output and maximum output.
GPH: Volumetric flow rate in gallons per hour.
GPM: Volumetric flow rate in gallons per minute.
Ground: 1. The electrical neutral line having the same potential as the surrounding earth. 2. The negative side of DC power supply. 3. Reference point for an electrical system.
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.
Handshake: An interface procedure that is based on status/data signals that assure orderly data transfer as opposed to asynchronous exchange.
Hardware: The electrical, mechanical and electromechanical equipment and parts associated with a computing system,
Heat Sink: 1. Thermodynamic. A body which can absorb thermal energy. 2. Practical. A finned piece of metal used to dissipate the heat of solid state components mounted on it.
Heat Transfer: The process of thermal energy flowing from a body of high energy to a body of low energy. Means of transfer are: conduction; the two bodies contact. Convection; a form of conduction where the two bodies in contact are of different phases, i.e. solid and gas. Radiation: all bodies emit infrared radiation.
Heat Treating: A process for treating metals where heating to a specific temperature and cooling at a specific rate changes the properties of the metal.
Heat: Thermal energy. Heat is expressed in units of calories or BTU's.
Hertz (Hz): Units in which frequency is expressed. Synonymous with cycles per second.
ID: Inside diameter
Infrared: An area in the electromagnetic spectrum extending beyond red light from 760 nanometers to 1000 microns (106 nm). It is the form of radiation used for making non-contact temperature measurements.
Insulated Junction: See Ungrounded Junction
Insulation Resistance: The resistance measured between two insulated points on a transducer when a specific dc voltage is applied at room temperature.
Interchangeability Error: A measurement error that can occur if two or more probes are used to make the same measurement. It is caused by a slight variation in characteristics of different probes.
Interface: The means by which two systems or devices are connected and interact with each other.
Intrinsically Safe: An instrument which will not produce any spark or thermal effects under normal or abnormal.
IP Rating: (or "Ingress Protection") ratings are defined in international standard EN 60529 (British BS EN 60529:1992, European IEC 60509:1989). They are used to define levels of sealing effectiveness of electrical enclosures against intrusion from foreign bodies (tools, dirt etc) and moisture.
IP66: First digit is the intrusion protection, in this case 6 is totally dust tight. Second digit is moisture protection, in this instance protection against string water jets and waves.
IP67: Total dust ingress protection and protected against temporary immersion between 15cm and 1m depth.
Isolation: The reduction of the capacity of a system to respond to an external force by use of resilient isolating materials.
Joule: The basic unit of thermal energy.
Junction: The point in a thermocouple where the two dissimilar metals are joined.
Kelvin: Symbol K. The unit of absolute or thermodynamic temperature scale based upon the Celsius scale with 100 units between the ice point and boiling point of water. 0°C = 273.15K (there is no degree (°) symbol used with the Kelvin scale).
Kilowatt (kw): Equivalent to 1000 watts.
Kilowatt Hour (kwh): 1000 watthours. Kilovolt amperes (kva): 1000 volt amps.
Kinetic Energy: Energy associated with mass in motion, i.e., 1/2 rV2 where r is the density of the moving mass and V is its velocity.
Laminar Flow: Streamlined flow of a fluid where viscous forces are more significant than inertial forces, generally below a Reynolds number of 2000.
Leakage Rate: The maximum rate at which a fluid is permitted or determined to leak through a seal. The type of fluid, the differential Limits of Error: A tolerance band for the thermal electric response of thermocouple wire expressed in degrees or percentage defined by ANSI specification MC-96.1 (1975).
Life Cycle: The minimum number of pressure cycles the transducer can endure and still remain within a specified tolerance.
Linearity: The closeness of a calibration curve to a specified straight line. Linearity is expressed as the maximum deviation of any calibration point on a specified straight line during any one calibration cycle.
Load Impedance: The impedance presented to the output terminals of a transducer by the associated external circuitry.
Load: The electrical demand of a process expressed as power (watts), current (amps) or resistance (ohms).
M: Mega; one million. When referring to memory capacity, two to the twentieth power (1,048,576 in decimal notation).
Mass Flow Rate: Volumetric flowrate times density, i.e. pounds per hour or kilograms per minute.
Maximum 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.
Mean Temperature: The average of the maximum and minimum temperature of a process equilibrium.
Method of Correction: A procedure whereby the mass distribution of a rotor is adjusted to reduce unbalance, or vibration due to unbalance, to an acceptable value. Corrections are usually made by adding material to, or removing it from, the rotor.
Mica: A transparent mineral used as window material in high-temperature ovens.
Microamp: One millionth of an ampere, 10-6 amps, µA.
Micron: One millionth of a meter, 10-6 meters.
Mil: One thousandth of an inch (.001").
Millimeter: One thousandth of a meter, symbol mm.
NB: Nominal Bore.
NEMA-4: A standard from the National Electrical Manufacturers Association, which defines enclosures intended for indoor or outdoor use primarily to provide a degree of protection against windblown dust and rain, splashing water, and hose-directed water.
NEMA-7: A standard from the National Electrical Manufacturers Association, which defines explosion-proof enclosures for use in locations classified as Class I, Groups A, B, C or D, as specified in the National Electrical Code.
NEMA-12: A standard from the National Electrical Manufacturers Association, which defines enclosures with protection against dirt, dust, splashes by non-corrosive liquids, and salt spray.
Noise: An unwanted electrical interference on the signal wires.
O.D.: Outside diameter.
Offset: The difference in temperature between the set point and the actual process temperature. Also, referred to as droop.
Output Impedance: The resistance as measured on the output terminals of a pressure transducer.
Output Noise: The RMS, peak-to-peak (as specified) ac component of a transducer's dc output in the absence of a measurand variation.
Output: The electrical signal which is produced by an applied input to the transducer.
Parity: A technique for testing transmitting data. Typically, a binary digit is added to the data to make the sum of all the digits of the binary data either always even (even parity) or always odd (odd parity).
Phase: A time based relationship between a periodic function and a reference. In electricity, it is expressed in angular degrees to describe the voltage or current relationship of two alternating waveforms.
Polypropylene: A polymer of propylene used as a thermoplastic moulding material. Doesn't soak up water, making it ideal for uses where it will be constantly subject to moisture.
PortaGraph Software: Portagraph II is a software application specifically written for use with Micronics flowmeters which simplifies the downloading and viewing of the instument’s logged data. Data may also be viewed in text format or exported to Excel for more detailed analysis. Also allows real time monitoring, where measured data is automatically captured sample by sample and displayed in either graph or data table format. Data logged in one set of units can quickly be converted to another set if required.
Positive Temperature Coefficient: An increase in resistance due to an increase in temperature.
Potential Energy: Energy related to the position or height above a place to which fluid could possibly flow.
Power Supply: A separate unit or part of a circuit that supplies power to the rest of the circuit or to a system.
PPM: Abbreviation for "parts per million," sometimes used to express temperature coefficients. For instance, 100 ppm is identical to 0.01%.
Primary Device: Part of a flowmeter which is mounted internally or externally to the fluid conduit and produces a signal corresponding to the flowrate and from which the flow may be determined.
Probe: A generic term that is used to describe many types of temperature sensors.
Process Meter: A panel meter with sizeable zero and span adjustment capabilities, which can be scaled for readout in engineering units for signals such as 4-20 mA, 10-50 mA and 1-5 V.
Range: Those values over which a transducer is intended to measure, specified by its upper and lower limits.
Rangeability: The ratio of the maximum flowrate to the minimum flowrate of a meter.
Rankine (°R): An absolute temperature scale based upon the Fahrenheit scale with 180° between the ice point and boiling point of water. 459.67°R = 0°F.
Real Time: The time interval over which the system temperature is sampled for the derivative function.
Reference Mark: Any diagnostic point or mark which can be used to relate a position during rotation of a part to its location when stopped.
Relay (Mechanical): An electromechanical device that completes or interrupts a circuit by physically moving electrical contacts into contact with each other.
Relay (Solid State): A solid state switching device which completes or interrupts a circuit electrically with no moving parts.
Remote: Not hard-wired; communicating via switched lines, such as telephone lines. Usually refers to peripheral devices that are located a site away from the CPU.
Repeatability: The ability of a transducer to reproduce output readings when the same measurand value is applied to it consecutively, under the same conditions, and in the same direction. Repeatability is expressed as the maximum difference between output readings.
Residual (Final) Unbalance: Residual unbalance is that unbalance of any kind that remains after balancing.
Resistance: The resistance to the flow of electric current measured in ohms (1/2) for a conductor. Resistance is function of diameter, resistivity (an intrinsic property of the material) and length.
Reynolds Number: The ratio of inertial and viscous forces in a fluid defined by the formula Re = rVD/µ, where: r = Density of fluid, µ = Viscosity in centipoise (CP), V = Velocity, and D = Inside diameter of pipe.
RFI: Radio frequency interference.
Secondary Device: A part of the flowmeter which receives a signal proportional to the flowrate, from the primary device, and displays, records and/or transmits the signal.
Sensing Element: That part of the transducer which reacts directly in response to the input.
Sensitivity Shift: A change in slope of the calibration curve due to a change in sensitivity.
Sensitivity: The minimum change in input signal to which an instrument can respond.
SI: System Internationale. The name given to the standard metric system of units.
Signal: An electrical transmittance (either input or output) that conveys information.
Spectrum: The resolving of overall vibration into amplitude components as a function of frequency.
Stability: The quality of an instrument or sensor to maintain a consistent output when a constant input is applied.
Temperature Error: The maximum change in output, at any measure and value within the specified range, when the transducer temperature is changed from room temperature to specified temperature extremes.
Temperature Range, Compensated: The range of ambient temperatures within which all tolerances specified for Thermal Zero Shift and Thermal Sensitivity Shift are applicable (temperature error).
Thermal Coefficient of Resistance: The change in resistance of a semiconductor per unit change in temperature over a specific range of temperature.
Thermal Conductivity: The property of a material to conduct heat in the form of thermal energy.
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).
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.
Time of Flight (TOF): describes a variety of methods that measure the time that it takes for an object, particle or acoustic, electromagnetic or other wave to travel a distance through a medium. This measurement can be used for a time standard as a way to measure velocity or path length through a given medium, or as a way to learn about the particle or medium (such as composition or flow rate).
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.
Transient Vibration: A temporary vibration or movement of a mechanical system.
Transit Time: A typical transit-time flow measurement system utilizes two ultrasonic transducers that function as both ultrasonic transmitter and receiver. The flow meter operates by alternately transmitting and receiving a burst of sound energy between the two transducers and measuring the transit time that it takes for sound to travel between the two transducers. The difference in the transit time measured is directly and exactly related to the velocity of the liquid in the pipe.
Transitional Flow: Flow between laminar and turbulent flow, usually between a pipe Reynolds number of 2000 and 4000.
Transmitter (Two-Wire): 1. A device which is used to transmit data from a sensor via a two-wire current loop. The loop has an external power supply and the transmitter acts as a variable resistor with respect to its input signal. 2. A device which translates the low level output of a sensor or transducer to a higher level signal suitable for transmission to a site where it can be further processed.
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.
Union: A form of pipe fitting where two extension pipes are joined at a separable coupling.
Vacuum: Any pressure less than atmospheric pressure.
Velocity: The time rate of change of displacement; dx/dt.
Vibration Error Band: The error recorded in output of a transducer when subjected to a given set of amplitudes and frequencies.
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.
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.
Voltage: An electrical potential which can be measured in volts.
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.
Watt Density: The watts emanating from each square inch of heated surface area of a heater. Expressed in units of watts per square inch.
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.
Zero Offset: 1. The difference expressed in degrees between true zero and an indication given by a measuring instrument. 2. See Zero Suppression
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