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Switch/Sensor Glossary of Terms ABS         Acrylonitrile Butadiene Styrene. A rigid black plactic, usually pipe, used for drain, waste & vent lines. Absolute instrument          An instrument whose calibration can be determined by means of simple physical measurements on the instrument. Compare to secondary instrument. Absolute pressure         Atmospheric pressure added to guage pressure. Absolute temperature Temperature based on an absolute scale. Absolute temperature scale A temperature scale based on absolute zero. Refer to the Kelvin temperature scale. Absolute zero A hypothetical temperature characterized by a complete absence of heat and defined as 0°K, -273.15°C, or -459.67°F. AC   Alternating Current, an electrical supply in which the polarity of the wire reverses rapidly. Access Panel   A covered opening that allows access to service a system, electrical, plumbing, etc.  Accuracy Closeness of an actual device's measurement to the value of a primary calibrated standard usually expressed as a percent of error at a degrees C. Degree of conformity of a measured value to a standard value; the closeness of a sensor's indication to the actual value of the material being measured. Accuracy rating A value that defines a a devices limit of measurement error that will not be exceed under the devices operating specifications. A number of quantity defining a limit that errors will not exceed when a device is used under specified operating conditions. Accuracy can be expressed in a number of forms, i.e. in terms of the measured variable (±1°C, percent of span (±0.5% of span), percent of upper range value (±0.5% of upper range value F.S.), percent of scale length (±0.5% of scale length) or percent of actual output reading (±1% of actual output reading). Acoustics The degree of sound emitted from the ultrasonic or radar transducer. Actual pressure The atmospheric pressure at the level of the barometer. Adapter            A fitting that joins two different types of pipe together, or joins threaded to non-threaded pipe ends. Admittance Admittance of an AC circuit is analogous to conductivity of a DC circuit; it is the reciprocal of the impedance of an AC circuit. Aeration           The turbulent mixing of water and air to dissipate pollutants into the air. Air Admittance Valve           A device that replaces a traditional vent to allow air to enter the pipe and equalize pressure, preserving the seal of water in the fixture trap. Air Check            A device that allows water, but not air, to pass through it. An air check is a typical component in treatment systems using a regenerant eductor. Air Gap            A device mounted at the back of a kitchen sink, connecting to the drain line between a dishwasher and disposer while preventing contaminated water from siphoning back into the dishwasher. Air Lock           Blockage of liquid flow caused by an air bubble in the line. Air Volume Control           Maintains the air change in a standard water storage tank. Air Check Valve           A check valve located in the riser of a wet pipe fire sprinkler system that sounds an alarm when water begins to pass through it. Alternating current (AC) A flow of electric current that undergoes periodic reverses in direction. Ambient The average process conditions around the Madison switch or sensor. Ambient pressure The atmospheric pressure of the medium surrounding a particular sensor. When no specific data is known the assumed value is 14.7 psia. Ambient temperature The average or mean temperature of the atmospheric air surrounding the sensor. If the sensor is a heat generator, this term refers to the temperature during the sensors operation. Ambient temperature compensation An automatic correction which prevents the sensor's indication from being affected by variations in ambient temperature. The device used to compensate will have a stated range within which the compensation is done. Ampere (A or amp) A unit of electric current flow, defined as the rate at which one coulomb of electric charge (6.25 x 1018 electrons) is transferred in a second. Amplifier A device that generates an output which is stronger than and bears some predetermined relationship (often linear) to its input. It generates the amplified output signal while drawing power from a source other than the signal itself. Angle Discharge Tube           A discharge tube that changes direction of the flow by 90 degrees. Angle Stop           A shutoff valve between water pipes and a faucet. The inlet connects to the water supply line and the outlet angles up 90 degrees to a faucet. Anode Rod           A sacrificial metal rod installed in a water heater to protect the tank from corrosion and extend tank life. ANSI            American National Standards Act Analog Pertaining to measurements or devices in which the output varies continuously, i.e. voltage or rotation signals. Compare to digital. Analog Output or signal A current signal that is a function of the measurement. A signal that continuously represents a variable or condition. Analog-to-Digital (A/D) conversion A term referring to the conversion of an analog signal into a digital signal. ANSI American National Standards Institute Antenna A conductor or system of conductors for radiating and/or receiving radio energy. API           American Petroleum Institute Aquastat           A thermostat that is submerged in water. It is used to control operation of a specific device. ASME           American Society of Mechanical Engineers ASHRAE           American Society of Heating, Refrigeration, Air Conditioning Engineers ASTM           American Society for Testing Materials AWWA           American Water Works Association Antenna feed The source of illumination for an antenna reflector. Atmosphere The envelope of air surrounding the earth and bound to it more or less permanently by virtue of the earth's gravitational attraction. A unit of pressure. Atmospheric pressure (barometric pressure) The pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the "column" of air lying directly above the point in question. Attenuation The reciprocal of gain; a ratio defining the decrease in magnitude of a signal as it passes between two points or two frequencies. May be expressed as dB. AWG American Wire Gauge BSL Best Straight Line (non-linearity) Back Flow           The act of water traveling from one system back into any part of the main distribution system (usually by siphoning). Back Flow Preventer           A devise to prevent backflow. Usually required for water suppy lines to prevent waste water entry. Back Pressure           Pressure that resists the flow of fluid in a piping system. Backlash Relative movement of a mechanical device that occurs when its motion is reversed. Backup A redundant safety system that is used when the primary system malfunctions. Baffle           An object placed in an appliance to change the direction of, or retard the flow of air, gas or liquids. Balancing Valve           A water valve that controls water flow and balances heat distribution to different locations. Ball Check Valve           A valve that uses a ball to seal against a seat to stop flow in one direction. Ball Valve           A valve that uses a ball to seal against the seat. Barlow's Formula           An equation that shows the relationship of internal pressure to allowable stress, nominal thickness and diameter. Barometric constant Factor relating the pressure and the height of a column of mercury, for example, 1 mb = 0.750062 mm, 1 mm = 1.333224 mb. Baud rate Serial communication data transmission rate expressed in bits per second (bps). Beam Angle The area of acoustic pulse transmission that spreads with distance over range. Bernoulli's Law           The principle that a stream of liquid or gas exerts less sideways pressure while in motion than while at rest. As a result, fluids seem to be drawn into the stream, but are really pushed in by higher outside pressure. Bimetallic thermometer A thermometer, the sensitive element of which consists of two metal strips which have different coefficients of expansion and are brazed together. The distortions of the system in response to temperature variations are used as a measure of temperature. Bipolar A signal range that has both positive and negative values. Boiler           A sealed tank where water is turned to steam for heating or power. Boiler Feed           A check valve controlling inlet water flow to a boiler. Boiling point Temperature of equilibrium between the liquid and vapor phases of a substance at a given pressure. Breakdown voltage A voltage level at which circuit components begin to be damaged. Brine           A strong solution of sodium chloride (slat) used in the regeneration of ion exchange water softeners. BTU           British Thermal Unit  A unit of heat energy required to raise the temperature of one pound of water one degree Fahrenheit. Burst Pressure           The internal pressure that will cause tubing to fail. Bushing             A pipe fitting used to join two pipes of different sizes. A bushing is threaded inside and out. Also a cylindrical part used as a lining or guide. CECC Cenelec Electronic Components Committee CFM           Cubic Feet per Minute CPe            Solvent, Chlorinated Polyethylene. A melting agent to form seams in shower pan liners. CPvC            Chlorinated Polyvinyl Chloride. Rigid plastic pipe used in water supply lines, where codes permit its use. Withstands high temperatures. CSST            Corrugated stainless steel tubing also called TracPipe. Calcium Carbonate            CaCO3  A white accumulation that forms in water lines, water heaters and boilers in hard water areas usually referred to as scale. Calcium Hypochlorite              CaCIO2  The matter adsorbed from a stream of water by activated carbon, and then extracted from the activated carbon with chloroform, using Calcium / Magnesium               Two of the principle elements that  when dissolved make water hard. Their presence contributes to the formation of scale & insoluble soap curds. Calibration Checking or adjusting (by comparison with a standard) the accuracy of a measuring device. To ascertain that the device's output corresponds to the information it is measuring. The process whereby a position on the scale of an instrument is identified with the magnitude of the signal (or input force) actuating the instrument. Calibration curve A graphical representation of the device's calibration over an operation range. Calibration cycle Applying known values to a device and recording of the corresponding output readings over that range of both ascending and descending directions. Calibration error The inaccuracy that the manufacturer permits when the unit is calibrated in the factory. Capacitance The capability of a device to store electric charge. Capacitance Sensing The space between two conductors effects an electric field between them. Carbonate Hardness              Water hardness due to the presence of calcium & magnesium carbonates & bicarbonates in water. Chamfer              Beveled end, usually done on pipe prior to threading. Check Valve              A type of backflow preventer installed in a pipe run that allows water to flow in only one direction. Chemical Compatibility Reaction of plastic, metal or elastomers corrosive material. Class I, Division  & Group             Class I is part of the National Electric Code definitions of hazardous location classifications and protection techniques.              Class I, Division 2 Products -- hazardous area flat panel computers               Group A: Atmospheres containing acetylene.              Group B: Atmospheres containing hydrogen, gases or vapors of equivalent hazard such as manufactured gas.              Group C: Atmospheres containing ethyl-ether vapors, ethylene, or cyclo-propane.              Group D: Atmospheres containing gasoline, hexane, naptha, benzene, butane, propane, alcohol, acetone, benzol, lacquer solvent vapors, or natural gas.             Group E: Atmospheres containing metal dust - including aluminum, magnesium, and their commercial alloys, and other metals of similarly hazardous characteristics.             Group F: Atmospheres containing carbon black, coal or coke dust.             Group G: Atmospheres containing flour, starch, or grain dusts. Close Nipple            Short lengths of pipe that are threaded on both ends. The threads may be close enough together they almost join in the center. Closed system            A system where the incoming cold water supply has a device that will not allow water to expand when heated. Coagulant            A material, such as alum, which will form a gelatinous precipitate in water, and cause the agglomeration of finely divided particles into larger particles which can then be removed by settling and or filtration. A coagulant aid may also be used to improve the effectiveness of the coagulant. Cold Draw           Pipe or tubing that is pulled through a die to reduce diameter and wall thickness. Compensated Hardness             A calculated value based on the total hardness, the magnesium to calcium ratio, and the sodium conscentration of a water. It is used to correct for the reductions in hardness removal capacity caused by these factors in cation exchange water. Compression Fitting             A kind of tubing or pipe connection where a nut, and then a sleeve or ferrule is placed over a copper or plastic tube and is compressed tightly around the tube as the nut is tightened, forming a positive grip & seal witout soldering.Also a flexable connector that has a nut & gasket designed to attach directly to an SAE standard compression thread. Compression Valve              A type of valve that is often used for water faucets. Condensate Condensed material resulting in water or ice based on temperature variants. Condensation is the process by which a vapor becomes a liquid. Water vapor that separates from products of combustion due to a reduction in heating surface temperatures to below the dew point of surrounding air. Water formed when water vapor formed in gas combustion loses heat before it passed out of the venting system. Conductance or Conductivity The measure of the ability of a liquid or solid to carry an electrical current. The reciprocal of resistance in a DC circuit is conductance. In water conditioning, the readiness of water to carry electricity. The unit of measure for conductance is the mho (reciprocal of ohm); it is used  to approximate the dissolved solids content of water. Continuous process control Uninterrupted in time, sequence, substance or extent. Controller A device that takes the switch or sensor input signal and uses relays to automate process equipment. Corrosion            The disintegration of a metal by electrochemical means. Corrosive Water             A water condition of low pH (acid condition) that can corrode metal pipes, fixtures, components & pumps; unbalanced water Coulomb The amount of electric charge transferred in one second by a current flow of one ampere. Cowl             A short fitting used to join two pieces of pipe. CPVC Chlorinated polyvinyl chloride – a cost-effective for metal piping operating up to 200°F, long service life, resists corrosion compatible with most inorganic chemicals salts acids & alkalis, do not use with organic chemicals such as aromatic oils & surfactants, no electrical conductivity, meets NSF for potable water; thermal expansion coefficient is 4.5 to 5 times higher than metal, support spacing must be designed with shorter spans than metal pipe. Crow's Foot              A PVC tee with twin outlets at right angles off the main. CSA Canadian Standards Association Current The rate of flow of electricity stated as 1 Ampere = 1 Coulomb per second. Cut Length             Wire, pipe or tubing cut to a specific length, usually per drawing or stated specification. Damping The suppression of oscillation. Dead Band The air gap distance in front of the ultrasonic or radar transducer that cannot be measured; the range through which an input can be changed without an observable response. The range through which the input may be varied without initiating a response. Usually expressed as a percent of full scale. Dead Time The interval between the introduction of change in input and the resulting observable response. Decibel Unit of measure (db) commonly used to measure the strength of an acoustic signal. Degree Rise             The difference bewteen the starting water temperature and the ending temperature after heating is complete. Deionization              The process of reducing water to a non-mineral state by passing it over a bed of resins. Deionized water               Water free of inorganic materials. Density Mass per unit of volume Desanco Fitting              A type of compression adapter that connects tubular brass fittings to PVC pipe. Dew Point              Temperature at which water vapor condenses to a liquid. Diaphragm              Flexible membrane in a valve that deflects down onto a rigid area of the valve body to regulate water flow from the supply line. May also be used to eliminate possible debris build-up within a valve. Die              Cutting device used to thread pipe. A set of these attach to die heads, and mounted on a threading device. Dielectric A non-conductor of DC current. Dielectric Constant Attraction between two opposite charges separated by uniform medium; a number that expresses the degree of non-conductivity of substances with full vacuum defined as 1.0. Diffuser             Device for reducing thevelocity and increasing the static pressure of a fluid passing through a system. DI             Abbreviation for deionization. Dip Tube             Tube inside the water heater that sends cold water to the bottom of the tank. DIN Deutsches Institut für Normung e.V. The German Institute for Standardization. Direct Current An electric current flowing in one direction that is a constant value. Discharge Head             Difference in elevation between the liquid level of the discharg tank and the centerline of the pump. Also includes any additional pressure head that may be present at the discharge tank fluid surface. Discharge Tube             Outlet tube that connects a disposer or pump to the drain line. Diverter             A valve that directs fluid to various outlets. Dope             Pasty lubricant used to seal pipe threads prior to making a threaded pipe connection. Double Horizontal Tee             A PVC tee with twin outles of a smaller diameter than the inlet. Double Wye Fixture             A fitting that has branches coming in at an angle from each side of the main to join the main run. Drain Valve             Valve designed to allow drainage of stored contents from a water heater. Drawdown            The distance the water level drops below the standing water level while the pump is operating. Drift Readings that wander from a set calibration point. This is an undesirable change in input/output relationship over time. The variation over a period of time in a devise's output when the input parameter is fixed. Temperature change is a common cause of drift. Duo Valve             A twin valve (hot & cold) with a single on/off lever used for washing machine boxes. Dynamic Pressure             The pressure when the water is flowing. ECO              Energy Cut Off. A safety device designed to shut power off to the water heater and prevent high temperature. EF Energy Factor              A measure of the overall efficiency, stand-by loss and energy input. EMI Electromagnetic interference. ERW             Electric Resistance Weld. Most common form of manufacture for pipe 2 3/8" to 22" in diameter.   Eccentric Shank             A shank or the fitting with a shank in which the centerline is offset to allow minor compensation for supply lines that would be difficult to precisely position. Eductor             A device utilizing a nozzle & throat, installed in a stream of water to create a partial vacuum to draw air or liquid into the stream. Efficiency            For plumbing, a product's ability to utilize input energy, expressed as a percentage. Elbow            A fitting with two openings that changes the direction of the line. Also known as an ell. Various angles from 22 1/2 degrees to 90 degrees; often referred to by their angles (i.e. 45, 90) Electric Resistance Weld Pipe (ERW)           Cold finished pipe made by a series of operations in which the flat rolled material is cold shaped into tubular form & welded at the seam.The heat for the weld is generated at the seam by the resistance to the flow of electric current applied through electrical contacts or an induction coi. Electrodialysys           A process which uses an electrical current & an arrangement of permeable membranes to separate soluble menerals from water. It is often used to desalinate salt or brackish water. Electrolysis           A process involving chemical change caused by the passage of an electric current through a liquid. Electrolyte           A nonmetallic substance that carries an electric current, or substance which, when dissilved in water, separates into ions which can carry an electric current. Elevation           The vertical distance between the level where fluid enters a pipe and the level where it leaves. For plumbing, it must be added to the total discharge head if the inlet is lower that the outlet and subtracted if the inlet is higher. End Body            A faucet valve body configuration in which both the inlet and outlet are at the end of the valve body. Endpoint            (1) The point at whicha process is stopped because a predetermined condition is met; (2) in an ion exchange water softener service run, this is where the hardness of the softener effiluent increases to a predefined concentration, often 1.0 grain per gallon; (3) in a filter service this may be where the pressure drop across the filter reaches a predetermined value. Energy Guide Label           The label required by the FTC on appliances that show an estimated annual cost of operation and how the applicance's efficency compares to all other comparable models. Error The difference between the measured signal value and actual reading and the true (ideal) or desired value. Excitation External voltage and current applied to a transmitter during operation. Expansion Tank             A tank designed to absorb excess pressure due to thermal expansion. (e.g. closed system) Expansion Valve             Thermostatically controlled valve that controls liquid refrigerant. Explosion Proof A device that can withstand an explosion of gases within it and prevent the explosion of surrounding gases due to sparks or hot spots, and maintain an external temperature that will not ignite the surrounding gases. Extrusion             Refers to the result of forcing molten metal or plastic through a die or mold to form a specific shape. Eye of the Impeller            The center of the impeller where the fluid enters. F Rating              A rating of effectiveness of firestop material, measuring its resistance to flames and water. FHT              Female Hose Thread FNPT              Female pipe thread in which the threads are on the inner side of the connection fitting. Fahrenheit temperature scale A temperature scale on which the freezing point of water equals 32° and the boiling point equals 212° at standard atmospheric pressure (760 mm Hg). Faucet Threads             Special thread size for fittings that connect to faucets. A cone seal or gasket is usually included because straight threads will not have a complete seal without a gasket. Feed Pump             A pump that supplies water to a boiler. Feed Water             Water introduced into a boiler during operation. It includes make-up and return condensate. Female Fitting            A fitting that receives a pipe or fitting. A fitting into which another fitting is inserted. Ferrous           Material containing or derived from iron. Ferrule           Metal cover piece for an opening. Fieldbus All-digital communication network used to connect process instrumentation and control systems. Designed to replace systems based on 4-20mA analog signals with bi-directional multivariable data communication capability. Fitting             Any pipe or tubing part used to join together two sections of pipe or tubing, such as elbows, couplings, bushings, bends, wyes, etc. Fixed Cone Valve             A cylinder gate mounted with the axis horizontal. Also know as Howell Bunger Valve. Flange             Extending rim or edge at one end of a pipe shaft that gives support or a finished appearance. Flare Fitting             A fitting used to connect flex copper pipe, usually gas pipe. Flex Coupling             Rubber coupling used to join DWV Pipe. Can be used to connect PVC pipe tp Clay or Cast Iron above or below ground. Also used to repairs with attached steel band clamps. Floats             A compinent of some liquid level measurement devices that contain a magnet and use material with a desired specific grafity. Flocculant             A chemical substance that promotes the aggregation or coagulation of suspended particles in the water. Flow Control Valve             Valve designed to reduce liquid flow to a plumbing fixture. Also a check valve that prevents flow reversal. Flow Rate             Rated in gallons per minute (GPM) or in gallons per hour (GPH). Flush Joint             A connection with both male and female threads cut into the pipe. Flux             Paste applied to copper pipes, fittings & wiring joints before soldering to help the fusion process & prevent oxidation. FM Factory Mutual Free Available Chlorine             The concentration of residual chlorine present as dissolved gas, hypochlorous acid or hypochlorite, not combined with ammonia or in other less readily available form. Freezing point Temperature at which a liquid solidifies under any given set of conditions. It may or may not be the same as the melting point or the more rigidly defined true freezing point or (for water) ice point. Frequency The number of cycles over a specific time during which an event occurs. Frequency modulation A type of modulation in which the frequency of a continuous radio carrier wave is varied in accordance with the properties of a second (modulating) wave. Friction Head Difference            The difference in head required to move a mass of fluid from one position to another at a certain flow rate within a piping system. It is also the specific energy required to overcome friction in the system. Friction Loss             The loss of pressure caused by the turbulence created in water while traveling through the pipe. FRP             Used to describe fiberglass reinforced plastic lined vessels. Full Hydraulic Capacity             The designed capacity of a pipe or conduit. Ga.             Abbreviation for gauge, wire size (also referred to as AWG) and the wall thickness of tubing Gain             In an electrical circuit, the amount of amplification used. An increase or amplification. There are two general usages of the term in radar meteorology: (a) antenna gain (or gain factor) is the ratio of the power transmitted along the beam axis to that of an isotropic radiator transmitting the same total power; and (b) receiver gain (or video gain) is the amplification given a signal by the reciver. Also referred to as antenna gain. GFCI             Ground Fault Circuit Interrupter. A device to cut off the flow of electricity if a short circuit is detected. Galvanic Action             The phenomenon of corrosion of an anode (positive terminal). When two dissimilar metals are immersed in an electrolyte, an electrical potential will exist   between them. If the two are in an electrical contact, a current will flow. The metal that becomes the anode (negative) of this cell will corrode and dissolve while the cathode (positive) will be protected from corrosion. Galvanizing             The process of applying a coating of zinc to the finished product to provide corrosion protection. The coating can be applied by hot dip or electrolytic deposition. Galvanometer              Laboratory instrument that detects & measures small electric current. Gasket              Flat device usually made of fiber or rubber used to provide a watertight seal between metal jounts. Gauge (gage)              Device for registering water level, discharge, velocity, pressure, etc. A number that defines the thickness of a sheet of metal. The larger the number the thinner the pipe wall. Gel / Grease Cap              Waterproof wire connector. Gradient              The rate at which an interogation pulse can propagate through waveguide and a strain pulse can be returned in terms of microseconds per inch. Grip Fitting              A compression-type fitting used on PB pipe. Gross volume Volume calculations based on API standards Ground Electrical neutral lead having the same potential as earth; the referance point for an electrical system. Connecting a piece of electrical equipment to a "ground wire" which is connected to the electrical system ground at the circuit breaker box. Hard Water             Natural water containing impurities in various proportions. Traditional hardness is a measure of calcium or dissolved solids in a solution, measured in parts per million. Hard water generally ranges from 100 to 250 ppm. Hardness             The amount of dissolved minerials in water measured in grains per gallon (GPG). The most common minerials are calcium & magnesium. HART Highway Addressable Remote Transmitter Hazardous Area The National Electrical Code uses ratings of Class, Division and to classify hazardous areas based on the types of hazardous material Head              The pressure of water (or steam) in a closed system. It represents the differential in the gravitational force exerted by a liquid at two different depths. Hermetic              Completely sealed, especially against the escape or entry of air. Hertz               Units in which frequency (Hz) is expressed that is synonymous with cycles per second. HVAC               Heating, Ventilation, and Air Conditioning Hydration              The chemical absorption of water into a substance. Hydraulic Pressure            That exists in a system containing non-compressible liquid. Hydrolysis               The reaction of a slat with water to form an acid and a base. Hydrostatic Pressure                Pressure that exists in a system containing non-compressible liquid. Hysteresis The maximum difference between two set points typically associated with control. The maximum difference in output for any given input (within the specified range) when the value is approached first with increasing, and then with decreasing, input signals. Caused by energy absorbed in the elements of the measuring instrument. Usually expressed as a percentage of full-scale range. ID            Inside diameter Impedance Opposition to the flow of AC current; the equivalent of resistance in DC circuits. The unit is in ohms. Inaccuracy The difference between the input quantity applied to a measuring instrument and the output quantity indicated by the instrument. The inaccuracy of an instrument is equal to the sum of its instrument error and its uncertainty. Indicator An instrument used to reveal but not necessarily measure the presence of an electrical quantity. It is used to display the output of a sensing element after suitable amplification and modification. Sometimes called a display. Inductance The property by which an electromotive force is induced in a conductor when the magnetic field is changing around it. This is usually caused by changes in the current flow in the circuit or in a near by circuit. Invert A term used when the measurement span is reversed from 4-20 mA or 20-4 mA. Impedance The total resistive and reactive opposition to electrical flow. Intrinsically Safe A device that cannot produce any spark or hot spot effects under normal or abnormal conditions that would ignite ambient conditions. A device or wiring which is incapable of releasing sufficient electrical or thermal energy to ignite a hazardous mixture of vapor. ISA Instrument Society of America ISO International Standards Organization Isothermal             Action that takes place with no change in temperature. Junction Box / J-box             Utility area where incoming current is connected in an electrical appliance. kPa             Kilopascal. A metric unit for pressure. 100 kPa = one atmosphere. KW             Kilowatt. A measure of the rate of supply of energy or power, equal to 1000 watts or 3412 BTU per hour. Kilowatt            One thousand watts. Langelier's Index            A calculated number used to predict wheather or not a water will precipitate, be in equilibrium with, or dissolve calcium carbonate. It is sometimes erroneously assumed that any water that tends to disolve calcium carbonate is automatically corrosive. Laser A narrow, intense beam of light. Leakage             Loss of fluid usually due to mechanical breakdown or gasket wear. Loop Power Analog circuit where the device's power and signal are delivered on the same two wires. Loop Resistance The total resistance of all sensors connected in series on a 4-20 mA circuit. LP           Liquid Propane mA (Milliamp) Milliamp is one thousandth of an ampere. mV (Millivolt) One thousandth of a volt. Magnesium             One of the elemensts in the earth's crust, the compounds of which when dissolved in water make the water hard. The presence of magnesium in water is a factor contributing to the formation of scale & insoluble soap curds. Male Fitting             Fitting that is inserted into another fitting. Male Threads             Threads on the outside of pipes & fittings. Measurement Signal             The electrical, mechanical, pneumatic, digital or other variable applied to the input of a devise. It is the analog of the measured variable produced by the transducer. Mechanical Controls            Dials, slides, switches, knobs, buttons, and so forth used to operate devices. Metal Fatigue            A breakage of the metal caused by the bending & flexing or the expansion & contraction of a metal part beyond its endurance limit. Micron            A uit of measure, one thousandth of a meter. Millivolt           One thousandth of a volt. Multiplexer (Mux) A switching device that sequentially connects multiple inputs or outputs in order to process several signal channels with a single A/D or D/A converter. NEC National Electric Code published by the National Fire Prevention Association. Negative Pressure              Less than atmospheric pressure. NEMA National Electrical Manufacturers Association. NPS             National Pipe Straight threads standard, same as IPS. NPT National Pipe Thread standard, same as IPS Noise Any undesirable electrical signal. Can come from AC power lines, motors, electrical storms, radio transmitters, or internal components. Non-Ferrous           Not containing iron Non-lnearity The deviation from the best fit straight line that passes through zero. Organic Matter            Plant & animal residues, or substances made by living organisms. Offset Usually refers to the 4 mA span set point. Ohmmeter A devise used to measure electrical resistance. Operating pressure The actual pressure at which the device operates under normal conditions. Maximum working pressure is the maximum permissible operating pressure at a specified temperature. This is the highest pressure to which the devise will be subjected during regular use. Output settling time The time required for an analog output voltage to reach its final value within specified limits. Output signal A signal delivered by a device or system. Outside Diameter (OD)             The diameter measured from the inside edge. Overtravel The part of a stroke which falls between the end of the calibrated range and the travel stop. Perforated Pipe              Pipe designed to discharge water through small, multiple, closely spaced holes in the pipe wall. PH              Potential Hydrogen. The hydrogen ion concentration of water to denote acidity or alkalinity, measured on a scale of 0 to 14. Below 7 denotes acidity; above 7 denotes alkalinity. Phase A time-based relationship between a periodic function and a reference. PLC Programmable Logic Controller. Polarity In electricity, the quality of having two charged poles, one positive and one negative. Port A communication connection. Potentiometer (POT)             An adjustable resistor used to vary the sensing distance. Power Supply A separate device that supplies power to a sensor or system. PP           Polypropylene Pressure Head           Pressure in a plumbing system. The unit of measure which is the vertical force exerted by water at a depth of one foot. Probe Usually a term used to describe a sensor shape or end that would protrude into the environment to be sensed. ProfiBus An industrial field bus network with network communications protocol PSI           Pound Per Square Inch psia Pounds per square inch absolute; the unit of pressure used when the zero reference is full vacuum. psig Pounds per square inch gauge; the unit of pressure used when the zero reference is the barometric pressure of the atmosphere. Radio frequency The frequency range between ultrasonic and infrared. Ramp The total (transient plus steady-state) time response resulting from a sudden increase in the rate of change from zero to some finite value of input stimulus. Range The upper and lower limit values over which the switch or sensor is set to function; between the limits within which a quantity is measured, received or transmitted. Reactance The opposition to the flow of AC current, which is created by either inductance or capacitance. As an example, a circuit's total impedance is the sum of reactance and resistance, and it is stated in ohm. Relay An electromechanical device that completes or interrupts a circuit by physically moving electrical contacts. Reliability The probability that a devise will perform its objective adequately for the period of time specified, under operating conditions specified. Repeatability The maximum difference between output readings when the same input is applied consecutively. Resistance/Resistivity The opposition to the flow of current in a DC circuit, unit is ohm. The resistance that will give a one-ampere current flow if one volt potential difference is applied in a circuit; Resistivity is the reciprocal of conductivity, its unit is the ohm/cm. Resolution The smallest change in input which produces a detectable change in the output signal. Resonance A condition of oscillation caused when a small amplitude of periodic input has a frequency approaching one of the natural frequencies of the system. Response time An output expressed as a function of time, resulting from the application of a specified input in a specified operating environment. RFI Radio Frequency Interference RS232 A standard interface between a computer input/output port and a peripheral device. Signal properties including time duration, voltage, and current, are specified by the Electronic Industries Association. RS485 A protocol similar to RS232 which permits data interchange on multidrop networks of up to 32 nodes using a single twisted pair cable. In order for this this protocol to be used, each device on a network must have some level of intelligence in order established orderly data transfer over a single path. Sanitary Fitting           Fitting that joins the assorted pipe system designed to allow soild material to pass through without clogging or attaching to the surface of the fitting. Scale factor The factor by which the number of scale divisions indicated by the device must be multiplied to compute the value of the measured variable. Sensing element The element that is directly responsive to the value of a measured variable. Sensitivity The minimum change in a physical variable to which a device can respond. Sensor A device that detects a variable by receiving data in the form of one quantity and converting it to data in the form of another quantity. Service Pressure           The range of pressure in the pressure tank during the pumping cycle, usually expressed in pounds per square inch gauge (PSIG). Setpoint A variable, expressed in the same units as the measurement, which sets either the desired target for a controller, or the condition at which alarms are to be triggered. Signal A variable that carries information about another variable that it represents. Soft Water             Water that has a low calcium & magnesium content. Solder             A metal alloy that is melted to create a fused joint between metal pieces. Also the act of melting solder into the joint. Solvent Weld             Any of the types of PVC pipe & fittings that are fastened together with solvent-based cement. Span The difference between the limits of the measurement range from zero to full scale; algebraic difference between the upper and lower expressed in the same units as the range. Span shift Any change in slope of the input-output curve. Specific Gravity The ration of material mass to the mass of the same volume of pure water at 4 degrees C. Specific Heat             Amount of heat required to raise the temperature of a kilogram of a substance one degree Celsius. SS             Stainless Steel Stability             The ability of an instrument or sensor to maintain a consistent output when a constant input is applied. Stand Pipe             Open vertical pipe that receives water from the vessel that secures a uniform pressure and minimal turbulence. Static Pressure             The pressure when no water is flowing. Static Water Level             The undisturbed level of water in a vessel or well before pumping. Steady-state A characteristic of condition, such as value, rate or amplitude, exhibiting only negligible change over an arbitrary, long period of time. Stiffness The ratio of change of force (or torque) to the resulting change in deflection of a spring-like element. Strain The ratio of the change in length to the initial unstressed reference length of an element under stress. Suspended solids             Solid particles in liquid which are not in solution. Sweating             Term for soldering. Also formation of condensation on the outside of devices. Synchronous            An action or event that is synchronized to a reference clock. Tee             T-shaped fitting with three openings that allow another pipe to be joined at a 90 degree angle, used to create branch lines. Teflon Tape             A fluorocarbon polymer with non-sticking properties used to wrap pipe threads to seal a joint. Temperature Coefficient             The amount of drift, in percent of full scale output, that might result from a 1°C change in ambient temperature. Temperature Rise             The number of degrees Fahrenheit that incoming liquid must be raised to reach the desired water temperature. Thermal Expansion             The effect of a material expanding when heated. Thermocouple             Small electric generator. Electron flow between the hot junction & cold junction creating millivoltage when exposed to temperature change. Device is two dissimilar metals. Thermopile             Apparatus that consists of a number of thermocouples combined so as to multiply the effect & is used for generating electrical current. Thermal shock An abrupt temperature change applied to a sensor. Time constant The time required to complete 63.2% of the total rise or decay of the device; systems may have a time constant for each of the components of the process. Time Delay A device that delays a control response by a defined period of time. Transducer A device that receives data in the form of one value and converts it to data in the the same or another form. Transmitter A sensor that has two or three wire configuration and a 4-20 mA signal output. Triac A solid-state switching device used to control alternating current circuits. Turbulent Flow             Fluid flow in which the velocity at a given point varies erratically in magnitude & direction. Twisted Pair Two insulated wires, usually made from copper that are twisted in a normal six turns or inch spiral pattern. UL Underwriters Laboratories UNC             Unified National Coarse Trread. A standard kind of coarse straight thread used on fittings, nuts, and bolts. Not for pipe. UNF            Unified National Fine Thread. A standard kind of fine straight thread used on fittings, nuts, and bolts. Not for pipe. Union            Three piece fitting that joins two sections of pipe, but allows them to be disconnected without cutting. Vacuum Any pressure less than atmospheric pressure. Valve           A device that regulates the flow or fluid. Vibration The periodic movement or oscillation of a device or system. Viscosity The inherent resistance of a substance to flow. Volt (V) The electrical potential difference between two points in a circuit. One volt is the potential needed to move one coulomb of charge between two points while using one joule of energy. Voltage An electrical potential which is measured in volts. Volumetric             Refers to measurement of volume rather than weight. Working Pressure             Maximum pressure of the operating system or device permissible. Wye             A Y-shapped fitting with three openings used to create branch lines. Allows one pipe to be joined to another at a 45 degree angle.

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