Reprinted from December 2008 Underground Focus Magazine What is electromagnetic pipe and cable locating? The detection of magnetic fields produced by current flow on metallic pipes and cables.

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60-cycle: alternating current whose frequency is 60 hertz. Access point: a bare metal spot on a pipe or cable whereby one end of the conductive transmitting antenna is attached.

Access point: a bare metal spot on a pipe or cable whereby one end of the conductive transmitting antenna is attached. View photo.

Active: a receiver response to a magnetic field generated by the transmitter.

Air lock: any receiver reading created by the transmitter’s energy leaving the transmitting antenna and not the pipe or cable. View movie.

Alternating current: the type of energy produced both by an electric power plant and the transmitter; energy that flows in two directions.

Apex: the topmost part of a signal circle. View photo.

Attracting field: a magnetic field whose energy moves toward another field; this field is not circular. Audio frequency: another name for low frequency.

Audio frequency: another name for low frequency. View movie.

Bad current: with the receiver held stationary, a peak response that fluctuates considerably. View movie.

Bottom receiving antenna: the lower half of stacked peak antennas. Circuit: when discussing electromagnetic theory, the name for current flowing on a conductor and through earth.

Close-end: the end of a line leg where the transmitter is located. View photo. <

Close-end ground: a metal making contact with earth at the end of a line leg where the transmitter is deployed.

Coil: wire, usually copper, wrapped around a core in a spool-of-thread-type fashion. View photo.

Coil orientation: the positioning of coil windings within a magnetic field. View movie.

Common ground: a shared metallic grounding connection amongst cable systems. View movie.

Concentric signal circles: the transmitter’s energy that orbits the pipe or cable at all distances from the pipe or cable. View photo.

Conductive: transferring the transmitter’s energy onto a pipe or cable by employing a metal-to-metal connection between the transmitter and the pipe or cable. Conductive transmitting antenna: a wire with two ends which connects the transmitter to 1) the pipe or cable and, 2) the earth. Conductor: a name for a metallic pipe or cable when discussing electromagnetic theory. Cross: a potential signal split on a piping system where the transmitter’s energy encounters three new line legs. Current: the flow of the transmitter’s energy on a pipe or cable.

Current flow reading: a measurement on the transmitter of the amount of energy leaving the transmitter. View photo.

Current level: an assessment of the amount of the transmitter’s energy at any point along the pipe or cable. View photo.

Current measurement: a receiver reading, usually displayed in milliamps, that is produced by stacked-peak antennas and estimates how much of the transmitter’s energy is located at the point of the reading. View movie.

Depth validation: the raising of the receiver a known amount to see if a new digital depth reading has increased by that known amount. View movie.

Digital depth: a pipe or cable depth estimation utilizing at least two stacked peak antennas situated a fixed distance apart. Direct current: the type of energy produced by batteries; energy that flows in one direction. Earth: soil.

Electronic null: a receiver response whereby two symmetrically and horizontally positioned peak antennas record identical signal strengths. View photo.

Energize: to transfer the transmitter’s energy to a pipe or cable. Far-end: the end of a line leg opposite of the transmitter location. Far-end ground: a pipe or cable’s metal component making contact with earth at the opposite end of a line leg from where the transmitter is deployed.

Frequency: the transmitter’s energy as measured in hertz or kilohertz. View movie.

Good current: with the receiver held stationary, a peak response that does not fluctuate. Ground: where an insulated metallic utility makes contact with earth.

Ground rod: a copper or aluminum rod ranging in length up to 16 feet that serves to ground a cable system. View movie.

Grounding device: a piece of metal driven into earth so that the conductive transmitting antenna may be attached. Hertz: the number of times current on a pipe or cable changes directions in one second. High frequency: any transmitting frequency 10 kilohertz and above up to 480 kilohertz. High-high frequency: any transmitting frequency from 200 kilohertz or greater. High-low frequency: any transmitting frequency greater than 1 kilohertz up to 10 kilohertz. Horizontal inspection of field: receiver readings that are obtained perpendicular to the pipe or cable location. Horizontally-positioned peak antennas: on a multiple antenna receiver, a pair of tire coils used to produce an electronic null response. Inductive: transferring the transmitter’s energy onto a pipe or cable without employing a metal-to-metal connection between the transmitter and the pipe or cable.

Inductive coupler: a type of inductive transmitting antenna that is not located in the transmitter but rather in the clamp that encompasses a cable. View movie.

Inductive transmitting antenna: a coil located in the transmitter whose purpose is to energize the pipe or cable without using a metal-to-metal connection. Insulation: coating on a pipe or cable that separates the metal from earth. Insulator: a break in a pipe’s metallic continuity.

Isolate: the ability to keep the transmitter’s energy away from non-target lines. View movie.

Kilohertz: 1000 hertz. Line leg: a single-direction section of a pipe or cable which has metallic continuity.

Logical or visual termination point: a trace that leads to an above-ground, utility-related structure. View movie.

Low frequency: any transmitting frequency below 10 kilohertz.

Low-high frequency: any transmitting frequency less than 200 kilohertz but greater than 10 kilohertz. View movie.

Low-low frequency: any transmitting frequency 1 kilohertz or below. Magnetic field: the product of alternating current flowing on a pipe or cable. Metallic continuity: a line leg that has no insulators or unarmored splices. Metallic path: the route on a pipe or cable which the transmitter’s energy follows. Metallic utility: a pipe or cable with metallic content. Metal-to-metal: another term for the use of a conductive transmitting antenna. Multiple antenna receiver: a receiver that employs two or more receiving antennas. Multiple-frequency transmitter: a transmitter that generates two or more frequencies. Neutral: a cable that provides metallic continuity between ground rods. Non-metallic utility: a pipe or cable with no metallic content.

Nonmetal-to-metal: another term for the use of an inductive transmitting antenna. View movie.

Non-target line: any pipe or cable not intended to be detected.

Not-round field: a magnetic field that is either an attracting or repelling field. View photo.

Null: a receiver response taken at the apex whereby the coil orientation is horizontal, like a tornado. View movie.

OK current: with the receiver held stationary, a peak response that fluctuates slightly.

Open end: a pipe or cable’s metal component not making contact with earth where a line leg terminates.

Parallel conductor: a conductor that has an optimum chance of being induced.

Passive: a receiver response to a magnetic field generated by something other than the transmitter. View movie.

Path of least resistance: the route the transmitter’s energy follows in order to return to the transmitter.

Peak: a receiver response taken at the apex whereby the coil orientation is vertical, like a tornado. View movie.

Perpendicular conductor: a conductor that has no chance of being induced. View photo.

Pumpkin-shaped field: the field that is produced by an inductive transmitting antenna. View photo.

Radio frequency: another name for high frequency. Receiver: a handheld antenna or series of antennas used to determine the strength and location of a magnetic field.

Receiver reading: signal strength, a peak or a null response, a digital depth reading or a current measurement.

Receiving antenna: a symmetric metallic winding induced upon by a magnetic field. View photo.

Resistance: anything that reduces current flow. Round field: a magnetic field that is not an attracting or repelling field. Signal: the part of a magnetic field that intersects a receiving antenna. Signal circle: the transmitter’s energy that orbits the pipe or cable at a particular distance from the pipe or cable. Signal decay rate: the diminishing strength of the magnetic field as the field travels away from the pipe or cable. Signal shape: a magnetic field that is either a round or not-round. Signal splits: a location along the pipe or cable where the transmitter’s energy can begin to travel on two or more new line legs. Signal strength: measurement of the magnetic field with a tire coil orientation. Single antenna receiver: a receiver that only employs one antenna. Single frequency transmitter: a transmitter which generates only a single frequency. Splice: a potential signal split on a cable system where the transmitter’s energy encounters multiple new line legs and the potential of going to earth. Stacked-peak antennas: two coils—a bottom receiving antenna and a top receiving antenna—which are both situated at the apex of two concentric signal circles. Target line: the pipe or cable intended to be detected. Tee: a potential signal split on a piping system where the transmitter’s energy encounters two new line legs. The path of least resistance: the metallic path which provides the transmitter’s energy the greatest opportunity to return to the transmitter.

Tire: a vertical coil winding that provides a peak response; windings that are orientated to the pipe or cable like a “tire to the road.” View photo.

Top receiving antenna: the upper half of stacked-peak antennas. View photo.

Tornado: a horizontal coil winding that provides a null response; windings that are orientated to the pipe or cable like a “tornado traveling down the road. View photo.

Trace: the entire section of a pipe or cable being located. Transmitter: a generator of alternating current, or energy; a miniature power plant.

Transmitting antenna: a metallic device used to transfer the transmitter’s energy from the transmitter to the pipe or cable. View photo.

Triangulation: a method for depth determination utilizing a single null antenna or a pair of horizontally-positioned peak antennas held at a 45-degree angle. View photo.

Unarmored splice: a break in a cable’s metallic continuity. View photo.

Un-bond: the physical detachment of one line leg from other line legs or a ground.

Vertical inspection of field: receiver readings that are obtained on top of the pipe or cable location. View photo.

Voltage: the amount of pressure behind the transmitter’s energy. Windings: the wire in a coil which is wrapped around the core.