Fisher M-97

Fisher M‑97 Valve & Box Locator: Technical Guide

Product Overview

The Fisher M‑97 is a rugged all‑metal detector designed to locate metallic items buried under soil, asphalt, or concrete. It is purpose‑built for finding valve boxes, manhole covers, vault lids, and other concealed metallic objects. The instrument detects both ferrous and non‑ferrous metals—including iron, steel, copper, aluminum, brass, nickel, and lead—making it suitable for varied utility applications. The device derives from earlier M‑95/M‑96 locators and introduces easier storage: the lower stem collapses, and the search coil folds flat to fit into an optional carrying case.

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Key Features and Benefits

• Simple user interface – The M‑97 uses only two knobs and a push‑button, simplifying operation. Operators can adjust sensitivity and ground balance quickly without navigating complex menus.
  
  
• Adjustable double‑locking shaft – The shaft length adjusts from approximately 38 to 50 inches and locks securely for stability. It collapses for compact storage.
  
  
• Ground‑Effect‑Rejection (GER) VLF technology – A very‑low‑frequency circuit rejects ground mineralization and wet or salty conditions, minimizing false signals from soil, pavement, or vegetation. Manual ground compensation allows precise tuning for challenging environments.
  
  
• High sensitivity with auto‑tune – The ultra‑slow auto‑tune feature stabilizes ground tuning and reduces frequency drift. Built‑in battery test and push‑button tuning help users maintain optimum sensitivity.
  
  
• Waterproof search coil options – Choose between 8‑inch and 11‑inch waterproof coils. Both coils are pressure‑sealed and perform in wet soil, mud, or shallow water. The optional 11-inch coil increases depth capability.
  
  
• Audio and visual feedback – The device provides a single‑tone audio response and an analog meter. The meter displays signal strength and polarity while the audio tone rises as the detector approaches a target. A headphone jack supports private listening, and battery life can exceed 25 hours when headphones are used.
  
  
• Compact and rugged – At only 3.3 lb (8‑inch coil) or 3.9 lb (11‑inch coil) and featuring a weather‑resistant housing, the M‑97 is easy to carry and built to withstand daily field use.
  
  
• Two‑year limited warranty – Fisher Research Laboratory backs the M‑97 with a two‑year warranty.
  
  

Technical Specifications

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How the Fisher M‑97 Works

User Interface

The M‑97 uses a straightforward control layout. Two rotary knobs control Ground Rejection and Sensitivity/Mode, while a large push‑button performs quick retuning. The analog meter displays battery strength and target signals, and a 1/4‑inch headphone jack allows private listening.

1. Power on and battery test – Turn the Mode knob to the Battery Test position and rotate the Ground knob to any number. A meter reading between 80 and 100 indicates full batteries.
   
   
2. Normal mode (Turn‑On‑and‑Go) – Set the Mode knob to Normal and the Ground knob to ~5. Press and release the Retune button to quiet the detector. Adjust the Sensitivity knob for desired depth; increasing sensitivity provides deeper detection but may require more retuning.
   
   
3. High mode – For maximum depth, switch the Mode knob to High. Use the Ground Rejection knob to balance the detector to local soil conditions, then retune as needed.
   
   
4. Manual ground compensation – In areas with mineralized soil or wet pavement, adjust the Ground Rejection knob until raising and lowering the coil does not change the audio tone or meter reading. This process eliminates false signals from ground effects and ensures the detector responds only to buried metal.
   
   
5. Retune button – Pressing the retune button rebalances the detector to the current ground conditions and resets the meter. Use this after moving to a new area or when the detector becomes unstable. The button also performs automatic sensitivity reset during quick tuning.

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Audio and Meter Feedback

The analog meter serves two roles: it measures battery strength in battery‑test mode and displays signal strength when searching. The audio tone rises in frequency as the detector approaches a target. In practice, operators use both audio and visual feedback to pinpoint the exact location of the buried object.

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Use of Headphones

Using headphones extends battery life and improves your ability to hear subtle audio changes. Fisher recommends headphones with cables shorter than three meters to meet safety guidelines. Do not use headphones near traffic or other hazards.

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Ease of Transport and Accessories

The M‑97 collapses for storage. To pack the unit, compact the lower stem, twist the search coil 90 degrees, and fold the coil flat. The optional carrying case provides a convenient transport solution. Accessories include coil covers, a vinyl carrying bag, and an 11‑inch search coil for deeper searches.

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Typical Applications

The M‑97’s versatile detection capabilities make it suitable for numerous utility and construction tasks:

• Valve and box location – Quickly locate valve boxes, curb valves, and service pedestals that have been paved over or buried under soil. The detector’s high sensitivity and push‑button retune enable fast pinpointing.
  
  
• Manhole cover and vault detection – Find cast‑iron manhole covers, vault lids, and meter boxes under asphalt or concrete. The double‑D coil penetrates several feet through soil and pavement.
  
  
• Survey markers and monuments – Detect survey markers, rebar, and property pins for surveying and mapping. Manual ground compensation allows stable operation in diverse soils.
  
  
• Construction and maintenance – Locate metallic obstructions before excavation to avoid damage to infrastructure. Because the M‑97 is not a line tracer, it should be used alongside pipe and cable locators when identifying non‑metallic lines.
  
  

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User Tips for Accurate Locating

Correct setup and operation of the M‑97 are essential for precise locating. Follow these manufacturer‑recommended practices to get the most out of your instrument:

• Set up the detector properly. Extend the lower stem until the search coil sits about 6–12 inches in front of your feet and keep your arm relaxed; wrap excess cable around the shaft with some slack and tighten the locking nut. Check the batteries by turning the Mode knob to Battery Test and the Ground knob to any number. A meter reading of 80–100 indicates good battery strength; lower readings reduce depth and accuracy, so replace the batteries as needed.
  
  
• Use the quick Turn‑On‑and‑Go tuning for routine work. In a metal‑free area, set the Mode knob to Normal and the Ground knob to 5. Raise the coil 12–18 inches above the ground and briefly press the Retune button; when you lower the coil, there should be little or no change in tone. If the tone changes, either move away from metal or perform precision tuning.
  
  
• Apply precision tuning when soil conditions are challenging or when using High mode. Start with Mode on Normal and Ground at 5, raise the coil 12–18 inches, press the Retune button, and listen. If the tone increases when you lower the coil, decrease the Ground setting slightly; if the tone decreases, increase it. Repeat until raising and lowering the coil produces little or no tone change.
  
  
• Sweep methodically. Do not swing the detector like a golf club. Move the search coil in a slow, half‑circle motion, keeping it at a consistent height above the surface. For small or deep targets, overlap your sweeps to avoid missing faint signals.
  
  
• Interpret signals and pinpoint edges. As the coil passes over metal, both the audio tone and the meter reading will increase. Large or deep objects may appear bigger than they are, so to outline the target, raise the coil slightly to reduce sensitivity and re‑sweep. Another technique is to detune the M‑97: move the coil away from the target, approach slowly, and press the Retune button as the tone rises. Repeat if necessary; detuning sharpens the response over the target, but over‑reducing sensitivity can make the target disappear.
  
  
• Reset the detector. After detuning or moving to a new area, raise the search coil away from metallic objects and press the Retune button to return to the original balanced settings.
  
  
• Use headphones when possible. The manufacturer notes that headphones (with cables under 3 m) improve battery life and help you hear subtle tone changes; avoid wearing headphones near traffic or other hazards.
  
  
• Follow general locating steps. Eastcom’s FAQ recommends a simple workflow for metal detectors: power on and calibrate, adjust sensitivity and settings, sweep slowly and methodically, watch the meter and listen to audio feedback, and mark the location when a signal is detected. This systematic approach helps ensure accurate locating with the M‑97.
  
  
• Remember its intended purpose. The M‑97 is a metal detector designed for finding valves, boxes, manhole covers, and other metallic objects. It should not be used as a substitute for a pipe‑and‑cable line tracer; use appropriate line‑tracing equipment when locating non‑metallic utilities.

By following these manufacturer‑recommended practices, operators can maximize the M‑97’s accuracy and efficiency when locating buried metallic objects.

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Why Choose Eastcom Associates for the Fisher M‑97?

Eastcom Associates, Inc. has been a trusted distributor of utility‑locating products in the Northeastern and Mid‑Atlantic United States since 1972. We stock a complete line of equipment for utility location, leak detection, fault location, and pipeline inspection, and are committed to offering superior service, selection, and value. 

More than simply supplying underground utility locators, Eastcom helps protect people, assets, and communities by bringing expertise and service to every excavation. Eastcom Associates prides itself on being the vendor of choice for customers and fostering an employee‑friendly culture that encourages growth. Our mission is to serve clients by supplying high‑quality products at competitive pricing while delivering exceptional customer service every day. 

Eastcom’s vision focuses on integrity, trust, commitment, service, teamwork, and quality. With decades of experience and a deep understanding of customers’ challenges, Eastcom offers expertise, service, and trusted solutions that keep every excavation safe.

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Contact Eastcom Today

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