Pearson Survey Instrument – Short Locator / Holiday Detector Tinker & Rasor


Caltech India offers Pearson Type Detector (PD)

The Model PD Detector and null Method have been well accepted by the industry. Acclaimed to be the fastest method known to accurately locate points of electrical contact and insulating joints on coated pipelines. This type survey may be conducted on coated pipelines regardless of their location. Unaffected by parallel lines, depths or cover, the survey can often be, in part, conducted from a moving vehicle over the pipe. In brief, the Null Method follows the flow of impressed audio frequency current in a coated pipe and determines where it leaves. The point of current discharge is determined by a sharp disturbance of the null itself rather than the signal level of the audio frequency. This method is quite practical, particularly as competent field personnel can interpret findings quickly and accurately.

The Pearson-Type detector is well known to industry, however, Tinker & Rasor’s Pearson-Type Detector, Model PD, is an all transistor instrument. It’s light weight, low battery drain and rugged construction are all features of this New Design. The PD Detector can be used to locate discontinuities in the coating of buried pipelines, to locate electrical contacts on the lines and to effectively locate the lines themselves. All of these findings can take place without the necessity of uncovering the pipeline under test. However, 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. The 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 shortings.


The new Mark IV Receiver employs a high gain, integrated circuit amplifier that is signal-to-noise optimized by three 750 cycle active filter elements. Modern circuit design insures maximum circuit stability even when operated at ambient temperature extremes. The filter attenuates a.c. and d.c. 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 oscillator provided with the set has been designed to use the latest developments in this type of instrumentation. A signal of 750 c.p.s. 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 (twelve volts) d.c. to stable audio frequency a.c. directly and hence, 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%. 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.

45/90 Probe

The 45/90 Probe, when used with the Tinker & Rasor Model PD Short Locator, allows for greater accuracy and tracing distances while locating electrical contacts and insulated joints on coated pipelines in corrosion control systems.

Use with all Model PD Receivers by simply plugging the probe jack into the “cleat” receptacle. Follow the same easy operating methods shown in the Model PD Instruction Manual for locating electrical shorts or pipe tracing.

The search coil is located in the tip of the probe head, which allows fast, accurate performance. When the search coil is in a vertical position, a sharp “null” indicates the center of the pipe or cable.

The depth of the pipe or cable can be accurately determined without the usual bending or kneeling. First locate center of the pipe or line “A” by crossing the pipe in a sweeping motion. A “null” (no signal) will mark the center of the pipe. Mark this location “A”, moving 90o from the pipe with bubble centered in 45o angle gauge and holding the probe tip close to the ground until another “null”- “B” is detected. This distance from “B” to “A” less ½ of the outside diameter of the pipe will be the depth of the buried pipe.


The “probe” itself is the red sensing element illustrated to the right. This elements plugs into a black telescopic handle assembly with a quick twist probe release fitting. The handle features a comfortable Neoprene grip handle and a 45o depth angle gauge on the side. A plug receptacle is located on top of the handle to accept the coiled cord from the Model PD Short Locator.

Operating Features:

  • Easy to operate
  • Unaffected by surface cover
  • Light weight
  • Rugged construction
  • Water resistant


  • Length: 34″ (864. mm)
  • Operating weight: 1 ½ lbs (0.7 kg)
  • Shipping weight: 4 lbs (1.8 kg)

Bumper Probe & Vehicle Clamp for PD Short Locator Models BP-1 & BP-1C

Pearson Survey Instrument

The Tinker & Rasor Model PD Short Locator has gained wide acceptance for its usage in locating electrical contacts and insulated joints on buried coated pipelines. The addition of the new Bumper Probe Model BP and vehicle clamp accessories serve to further enhance its operation, because the operator rides in the vehicle. The Bumper Probe is easily mounted on almost any field vehicle with a clamp made especially for this purpose. Twenty-five feet of cable are furnished to reach from the probe to the PD Receiver positioned in the vehicle with the operator.


  • Rugged construction
  • Water resistant
  • Unaffected by surface cover
  • Easy to install

Ordering Guide

BP-1 Probe and cable
BP-1C Probe, cable and vehicle clamp

Optional Accessories

  • Cadmium plated clamp
  • Short 6′ coiled cable


  • Probe size 1″ dia. x 91/4″ length (25.4 x 235 mm)

Shipping weight

  • Probe 2 lbs (0.9 kg)
  • Probe with clamp 4 lbs (1.8 kg)

In India, we have various customers from Mumbai, Delhi, Bangalore, Chennai, Hyderabad, Ahmedabad, Kolkata, Surat, Pune, Jaipur, Lucknow, Kanpur, Nagpur, Visakhapatnam, Indore, Bhopal, Patna, Vadodara, Ghaziabad, Ludhiana, Coimbatore, Madurai, Nashik, Srinagar, Aurangabad, Dhanbad, Allahabad and Ranchi in India.

error: Content is protected !!