A Pearson-type detector can be used successfully only if a pipeline has been carefully backfilled and the soil is compact around it. There also must be some moisture content in the surrounding soil. Cleats are worn by two inspectors walking in tandem. The cleats are terminated by cable connections to a receiver worn on the belt of one inspector. They enable him to accurately find holidays or large discontinuities in pipe coatings. The search coil can locate the pipe or any shorts.
Mark IV Receiver
Modern circuit design insures maximum circuit stability even when operated at ambient temperature extremes. The filter attenuates AC and DC interference. The search coil is contained within the receiver and has low impedance of 2,000 ohms. Although earphones are furnished for operator’s optional use, the loudspeaker offers advantages related to safety, convenience, and comfort. Built-in battery test and signal intensity meter of modern full-face design for ease of observation. Multi-directional depth level gauge for accurate (within 1 inch) depth determination.The New Mark IV Receiver employs a high gain, integrated circuit amplifier that is signal-to-noise optimized by three 750 Hz active filter elements.
In order that a maximum of energy can be transferred from the oscillator to the pipe, the output of the oscillator is provided with taps so that voltages of 2.5, 5, 7.5, 15, 50 and 100 Volts are available to match the load. An interrupter is provided to make the signal more easily recognized.The oscillator provided with the set has been designed to use the latest developments in this type of instrumentation. A signal of 750 Hz is generated by using a power transistor switching circuit. This arrangement eliminates troublesome vibrators, buzzers or other moving part elements. The transistor oscillator converts low voltage (12 V) DC to stable audio frequency AC directly. By a highly efficient method, the input current to the oscillator is only 1.7 amperes for a full output of fifteen watts, a conversion efficiency of better than 80%.