Schonstedt Instrument GA-72Cd Instruction Manual

Magnetic locator
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The Model GA-72Cd
®
Magnetic Locator is a product of over forty-six years experience in producing the world's finest flux-gate magne-
tometers and magnetic detectors for aerospace, military and civilian applications.
knowledge obtained from manufacturing under the most rigid quality control standards. The heart of the GA-72Cd
Schonstedt HeliFlux
®
magnetic field sensors. These sensors, acknowledged to be the world's finest, make possible the unequalled
performance of the locator.
December 1998
Schonstedt Instrument Company
Instruction Manual
Model GA-72Cd
Magnetic Locator
Manufactured By
Schonstedt Instrument Company
Global Detection Systems
Specializing in Professional Detection Systems
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Preface
Since 1968
®
The GA-72Cd
incorporates the
®
is its patented

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Summary of Contents for Schonstedt Instrument GA-72Cd

  • Page 1 Magnetic Locator is a product of over forty-six years experience in producing the world’s finest flux-gate magne- ® tometers and magnetic detectors for aerospace, military and civilian applications. The GA-72Cd incorporates the knowledge obtained from manufacturing under the most rigid quality control standards. The heart of the GA-72Cd ® is its patented Schonstedt HeliFlux ®...
  • Page 2: Table Of Contents

    Warranty/Shipping Information ............... 18 Schonstedt Instrument Company...
  • Page 3: Operation

    The Model GA-72Cd Magnetic Locator detects the magnetic field of ferromagnetic objects. It responds to the difference in the magnetic field between two sensors which are spaced about 14 inches apart. The GA-72Cd is unique because it provides an audio signal, and visual indications of both signal strength and polarity.
  • Page 4: Turn-On, Sensitivity And Volume Settings

    Turn-On, Sensitivity and Volume Settings Turn on the GA-72Cd by rotating the On/Off-Sensitivity control knob clockwise to position 1. This sets the sensitivity to what is referred to as the Normal Range (the L meter indication). You can increase the sensitivity by rotating the Sensitivity control clockwise to select M, H, or XH settings as indicated on the meter’s GAIN display.
  • Page 5: Audio Ouput Selection

    Audio Signal with Output Switch set to “A” No audio signal is heard until the GA-72Cd comes within detection range of a ferromagnetic object. As you move the locator across the object, frequency of the signal does not change but unit increases in volume over the object, then decreases in volume and turns off when the locator is moved out of range.
  • Page 6: Search Procedure

    Figure 6. Figure 5. Searching With the Locator When the GA-72Cd is positioned directly over a vertical pipe, the audio and digital indications will peak. The expanding bar graph and digital readout may be either a positive or negative level.
  • Page 7: Application Notes

    The signal from a rusty bolt or other small item (see Figure 9.) decreases much faster with distance than the signal from a larger target such as a 18-inch length of 3/4 rebar which can be located at depths up to 7 feet. Schonstedt Instrument Company...
  • Page 8: Strongly Magnetized Markers

    The two weaker indications occur because the locator is extremely sensitive to the magnetic field components parallel to its long axis. At point B and C the field is perpendicular to the locator so no peak audio of digital indications are produced at these points. Schonstedt Instrument Company...
  • Page 9: Correct Stake Orientation Is Important

    The great length of a well casing provides a strong field at the surface that makes it easy to locate casings buried up to 15 feet deep. Figure 13. Locating Water Figure 12. Locating Manhole Covers Well Casings Schonstedt Instrument Company...
  • Page 10: Locating Objects Under Snow Or Water And Traced Barbed Wire

    The GA-72Cd can be used to precisely locate the metal handles or reinforcing bars on septic tank covers at depths up to 4 feet. + OR - + OR - AUDIO SIGNAL Figure 14. Signal Patterns Provided by Septic Tank Covers Locating Objects Under Snow or Water and Tracing Barbed Wire The locator can be used in snow or in flooded areas - just keep the electronic unit out of the snow or water.
  • Page 11: Searching Areas Along A Chain Link Fence

    Figure 17. Searching in the Vicinity of a Chain Link Fence SIGNAL NULL WITH LOCATOR AS SHOWN 1- 5/8 Figure 18. Placement of Locator while Searching along a Chain Link Fence Schonstedt Instrument Company...
  • Page 12: Locating Valve Boxes

    Return to an area of maximum signal strength and hold the locator several inches above the surface. The sensitivity will probably have to be reduced during this second pass. Four-inch pipes can be located at depths up to 8 feet. Schonstedt Instrument Company...
  • Page 13: Locating Steel Drums

    Locating Steel Drums As shown in Figure 21, the GA-72Cd’s signal pattern will vary depending on the vertical or horizontal orientation of the drum and also how deep it is buried. A fifty-five gallon drum can be located at depths up to 8 feet.
  • Page 14: Locating Ordnance And Weapons

    As shown in Figure 22, a magnetized nonmetallic fiber optic cable is easily identified by the GA-72Cd’s visual indication which changes from positive to negative every six feet along with the audio signal which also peaks every six feet. VISUAL SIGNAL...
  • Page 15: Additional Applications

    1. People drilling in an area where hazardous materials might be encountered should use the GA-72Cd to search the area prior to drilling. Other Schonstedt gradiometers are available that can be lowered down the drill hole for periodic checks as drilling progresses.
  • Page 16: Data Logger Output

    Replacement of Batteries The GA-72Cd is powered by two 9-volt lithium batteries which have a shelf life of ten years, and provide twice the operating life of alkaline batteries. Access to the batteries is obtained by loosening the four captive screws and removing the electronics cover as shown in Figure 24.
  • Page 17: Troubleshooting Guide

    Loose connector(s) Visually inspect Reconnect Weak batteries Replace Uncontrollable screaming *Most battery manufactures’ warranties cover the cost of repair or replacement of any device damaged by their batteries. Removing batteries that leak will void their warranty. Schonstedt Instrument Company...
  • Page 18: Ga-72Cd Repair Parts

    Schonstedt Instrument Company...
  • Page 19: Service Information

    Nominal Sensor Spacing: ....14 in. (35.6cm) Construction: ......Rugged, all solid state Schonstedt Instrument Company...
  • Page 20: Warranty/Shipping Information

    LIMITED WARRANTY The Schonstedt Instrument Company (Schonstedt) warrants each product of its manufacture to be free from defects in material and workmanship subject to the following terms and conditions. The warranty is effective for 3 years (with the return of the Customer Registration Card) after the shipment by Schonstedt to the original purchaser.

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