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Electromagnetic Utility Locating
Most utilities are located using electromagnetic locators. The equipment consists of two components a transmitter used for applying a signal and a receiver used to pick up the signal.
For electromagnetic locating to work the transmitter must be able to apply a signal to an insulated, metallic cable or pipe. Examples include: telephone; electrical and CATV lines; tracer wires (often buried with plastic or other non-metallic pipes); gas and water metallic pipes; and finally security, fire or lighting systems.
PULS, Inc. uses only state-of-the-art electromagnetic locators from such manufacturers as Radiodetection, Metrotech and 3M.
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Electromagnetic Locating Methods
| Direct Connection - Direct Connection is the preferred method for locating utility lines electromagnetically. It is the most accurate method providing the greatest number of options for locating a buried utility line. |
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The transmitter is placed next to an access point for the utility line being traced (typically a utility box, utility vault, valve or other point where contact with line can be made). A line from the transmitter is connected to the utility and a second line is connected to an earth ground. |
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The transmitter is adjusted for power output and frequency to match the properties of the line being traced and the surrounding soil and other utilities. |
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The receiver is set to the same frequency as the transmitter and the signal which is sent from the transmitter through the utility line is traced on the surface. |
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| Induction - Induction is used when there is no surface access to a buried utility line. |
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The transmitter is placed on the surface and over the point where the target line is believed to run. |
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The line is then traced as with Direct Connection. |
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Sonde - A locating sonde is used when there is surface access to a buried pipe but the pipe is non-metallic. The sonde is simply a beacon that radiates a set frequency which can be traced by a receiver. Typical applications include empty conduit and drain or sewer pipes. |
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The sonde is pushed or pulled through the pipe and then traced as with Direct Connection.
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