Tinker & Rasor PD User Manual

Tel: [phone] Fax: [phone]

P. O. BOX 1667 SAN BERNARDINO, CA 92402

Web: www.tinker-rasor.com E-mail: [e-mail]

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Sponsoring members of NACE International, NACE Foundation

QMF-570 104-154

PRODUCT INSTRUCTIONS

MODEL PD

PEARSON DETECTOR

FIVE SECTIONS of QUICK INFORMATION

I. Model PD Functions
II. Operation Methods
III. Apparatus
IV. Instructions for Unpacking & Inspection
V. Operating Instructions

TINKER & RASOR MODEL PD PEARSON DETECTOR

I. Model PD Functions
A. Pearson Type Holiday Detector
The Tinker & Rasor Pearson type detector was designed to locate discontinuities, flaws or breaks in the

coating of buried pipelines. This method makes possible the exact location of coating breaks in buried lines without
access to the surface of the coated pipe. Locating electrical discontinuities aids in evaluating the application of a
coating and also these discontinuities can be repaired to eliminate corrosion and to reduce the amount of current
required for cathodic protection.

B. Short Locator
The apparatus is also effective in locating shorts or undesirable electrical contacts to buried coated pipe.

Such electrical contacts should be removed prior to placing a pipeline under cathodic protection, as these contacts
would drain a large amount of protective potential from the coated pipe.

C. Pipe Locator
The apparatus can be used very effectively as a pipe locator on coated pipelines that are electrically

connected by a screw or welded joints. This application is particularly effective where it is desired to locate and
follow one pipeline along a right-of-way where there are a number of buried lines.

II. Operating Methods
A. Pearson Survey Method
The method used to locate discontinuities is that of applying audio frequency AC energy between the coated

pipe and ground. A traverse along the pipeline is made in which the difference in potential is indicated across
approximately twenty to thirty feet of soil above the line. This potential difference is noted in the Receiver. When

Tel: [phone] Fax: [phone]

P. O. BOX 1667 SAN BERNARDINO, CA 92402

Web: www.tinker-rasor.com E-mail: [e-mail]

- 2 -

Sponsoring members of NACE International, NACE Foundation

QMF-570 104-154

PRODUCT INSTRUCTIONS

an area is reached where the difference in potential is considerably greater than the average potential over the
pipe, a discontinuity is assumed to lie under this area.

B. Method of Locating Shorts
The method of locating shorts or contacts on a coated pipe is that of applying a relatively large amount (5

to15 watts) of audio frequency AC between the pipe and a remote ground connection. A traverse is made along
the pipeline with a Receiver equipped with a search coil. A short or contact is observed along the traverse where
the average AC signal picked up over the line suddenly drops to a very low level. This is assumed to be a point
directly above the contact.

C. Method of Locating Pipe
An audio frequency AC signal is placed between the coated pipe and a good ground connection. The

Receiver, containing a search coil, is passed over the area where the pipe is assumed to be located. As the
Receiver is moved back and forth in a horizontal plane over the pipe, a sharp null will occur in the received signal.
The pipe to be located is assumed to be directly under this null. A well-coated pipeline can be followed for a very
great distance by this method when audio power of from five to fifteen watts is applied to the coated pipe.

III. Apparatus
The complete apparatus furnished with the Pearson-type detector comprises the following:
A. Solid state Oscillator

B. Solid state Receiver with filter
C. Lightweight headphones w/plug and cushions
D. Shoe cleats
E. Connecting cables
F. Carrying Case

A. Oscillator
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 Oscillator converts low voltage (12
volts) DC to stable audio-frequency AC directly; hence, by a highly efficient method, the input current to the
Oscillator is only 1.7 amperes for a full output of 15 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. The Interrupter is actuated by a switch on the
panel of the Oscillator. The Oscillator will produce 15 watts of 750 Cycle signal into a 500-ohm load with the output
selector set at the 100 volt position.

NOTE: Model PD-C (Rev. B) uses a new crystal that produces an interrupt frequency at a faster rate than
previous models. Users familiar with this instrument may notice the difference.

B. Receiver