Fisher Research Labs Pro-Arc User manual

Professional
Metal Detector
for the Archaeologist
USER’S MANUAL

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The PRO-ARC is a professional-grade metal detector, designed specifically for the
Archaeological professional. It comes in a heavy duty travel case and includes
everything you will need on the dig site.
The best technology from the oldest company in the business, the PRO-ARC, by Fisher®!
PRODUCT FEATURES
• Lightweight and well-balanced: best ergonomically engineered detector in the
industry.
• Intuitive menu-driven user interface
• Large LCD screen
• Visual indicators of important values such as:
Target Identification
Target Confidence
Target Depth (both running-depth and pinpoint-depth) Ground Mineralization
• Multiple Search Modes:
Discrimination
Static All Metal
Motion All Metal
• Trigger-actuated FASTGRAB™ ground balancing with manual override

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• Waterproof 11-inch open-frame BiAxial™ searchcoil
Housing constructed of a carbon fiber-polycarbonate blend
• Optional 5” BiAxial™ searchcoil
• Trigger-actuated target pinpointing with variable audio pitch
• Fully Adjustable Armrest
• Display backlight for night and low-light conditions
• Notch and discrimination controls
• Covers provided for both the control housing and battery box
• Durable travel hard case and battery charging kit
• Pin flags and Rite-in-Rain notebook
• Headphones
• Made in the USA
If you have any questions, or need assistance with your metal detector,
Call 1-915-225-0333, and ask for Fisher Hobby Technical Service
Copyright Fisher Research Labs, Inc., 2012

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Table of Contents
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-7
Quick Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9
Mechanicals
Assembly Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-13
Mechanicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-15
Armrest adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Using Headphones (included) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Introduction to the PRO-ARC
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18-19
Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20-23
Menu System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24-25
Ground Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26-31
Motion All Metal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32-33
Static All Metal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34-35
Discrimination Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36-45
PinPoint Feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46-47
LCD Visual Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48-53
Numeric Target Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48-49
Probable Target Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49-50
Depth Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
Confidence Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

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Fe3O4Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
Battery Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Ground Balance (GB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Setting Indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52-53
Backlight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Frequency Shifting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54-55
Capabilities & Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..56-61
Tips & Techniques
Search Techniques
How to sweep the searchcoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62-63
Boost and Cache Locating Processes . . . . . . . . . . . . . . . . . . . . . . . . . . .63-65
Pinpointing targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65-66
Estimating target size and depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66-68
False signals and chatter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68-70
Ground minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70-71
Hot Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71-72
Adjusting Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Tips on ground balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73-75
Shallow Water Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75
Salt Water Hunting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
How metal detectors work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76-77
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Back Page

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Specifications
Mechanical: S-rod with electronics housing mounted on handgrip, 3-piece
breakdown, batteries under elbow, 2-way armrest adjustment -
forward/backward & around forearm.
Searchcoil: 11” (28 cm) open-frame elliptical double-D, waterproof.
Batteries: 4 AA, alkaline (included).
Weight: 3.5 pounds (1.6 kg) with alkaline batteries installed.
Static Balance: force in vertical plane normal to elbow 0.47 pounds (0.22
kg).Varies with adjustment and user's stance and arm/hand
physiology.
Dynamic Balance: axial moment, 0.29 foot-pounds (0.39 newton-meters). Varies with
adjustment and user's stance and arm/hand physiology.
Sweep Effort: lateral moment 5.2 foot-pounds (7.1 newton-meters).
Operating Principle: VLF induction balance
Operating Frequency: nominal 13 kHz, quartz crystal timing reference 13158Hz,
13100Hz, 1043Hz, 12987Hz, 12931Hz, 12876Hz, 12821Hz

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Basic Sensitivity: 6 x 10 9 root Hertz (detectivity)
Lag Coefficient: 78 milliseconds
Reactive Overload: Approximately 10,000 micro-cgs units (volume susceptibility)
40,000 micro-cgs units with sensitivity < 30.
Resistive Overload: Approximately 1,200 micro-cgs units (volume susceptibility) 4,800
micro-cgs units with sensitivity < 30.
Ground Balancing Range: From ferrite to salt, inclusive
Discrimination
Ground Suppression: Combination of second and third order methods
ID Ground Suppression: Third order
Battery Life: Typically 40 hours with high quality alkaline batteries
Estimated 80 hours with nickel oxyhydroxide batteries
Estimated 65 hours with lithium iron disulfide batteries
Operating Temp Range: 4 to +122 degrees F (-20 to +50 degrees C)
Operating Humidity Range: 0-90% non-condensing

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Quick Start
Use your PRO-ARC right out of the case
1. Assemble the detector (see instructions beginning page 10).
2. Install four AA alkaline batteries. All positive (button-end) terminals point up.
3. Turn the knob, located under the armrest, fully clockwise. This turns the machine on and
sets audio volume to maximum.
4. When first turned on, the PRO-ARC starts out in the Discrimination Mode, with:
Sensitivity preset to 60
Discrimination Level preset to 10
Number of Tones preset to 3
Process# preset to dE
Sweep the searchcoil from side to side, parallel to the ground. Keep the searchcoil
moving over the ground. If you stop moving the searchcoil, the sound will also stop.
Probable target type will be indicated at the top of the LCD screen.
5. If the searchcoil is not in motion and not close to metal, the detector should be silent.
6. If you experience false signals from electrical interference, from the soil itself, or from lots
of trash metal, press the MENU button.
Sensitivity will be highlighted.

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Quick Start (continued)
Rotate the Settings knob to the left (counterclockwise),
Reduce the sensitivity setting until the false signals go away.
After 7 seconds, the machine will exit the menu and return to normal operation.
7. Find a patch of ground free of metal, toss a coin on the ground and sweep back and forth
over it a few times to get a feel for how the machine responds.
8. You are now ready to search.
9. Pull and hold the trigger switch with your index finger to pinpoint the exact location of
targets, making them easier to unearth.
When the trigger is pulled, PinPoint is engaged ….
The searchcoil need not be in motion to detect an object.
The 2-digit numeric display indicates approximate target depth, in inches.

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Assembly
1. Remove all components from box.
2. Attach searchcoil to lower rod by lining up the holes.
Push coil knob through hole and tighten knob gently.
You will tighten up the coil knob later.
3. Insert smallest rod into S-rod (S-rod holds detector body).
Turn top locking collar counterclockwise to open up. Push in pin on small rod. Slide
small rod into upper rod. Click pin into hole and tighten locking collar firmly clockwise.
4. Push lower rod into small rod as follows:
Turn locking collar counterclockwise to open up. If plastic insert tab interferes, push it
down, or turn tube upside down. Push in pin to allow rod to slide in. Slide lower rod in.
Click pin into any hole.
5. Remove Velcro strip from lower rod.
6. Wrap cable around stem as follows:
Leave some slack in cable at base of lower rod. Secure cable at base of rod with Velcro
strip. Wrap cable loosely around entire stem up to bent part of upper rod. You will re-wrap
the cable later after sizing the rods to your height.
7. Push cable into connector on back of housing.
Do not twist the cable or plug.

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Assembly (continued)
8. Tighten knurled cap nut by hand to secure cable connection to housing. Use minimal
finger pressure to start thread. Do not force threads. Nut may not completely cover
all threads when fully engaged.
9. Adjust to your height:
Hold detector, standing up, with your arm in the armrest. Place searchcoil flat on the
ground with back edge of coil 6” in front of your toes. Click pin on lower rod into nearest
hole. Firmly tighten bottom locking collar to secure lower stem.
10. Attach cable to top of rod with upper Velcro strip.
11. Tighten up coil knob to keep searchcoil from flopping.
12. Insert batteries.
4 batteries are all installed the same way -- positive terminals pointed upward.
After establishing a comfortable length, firmly tighten the locking collars on the rods to
prevent the tubes from rattling. Rotate the collars a full 270° to engage and lock in place.
If you are unable to rotate a full 270°, use gloves for a better grip.
If the searchcoil appears crooked with respect to the pole, loosen both locking collars and
re-adjust. Hold each of the lower poles in the counterclockwise position as you tighten
the locking collars.

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Searchcoil
Cable
Knurled
knob
Biaxial
Searchoil
Locking
Collar
Locking
Collar
Velcro
Strap
Velcro
Strap
Cable
Plug
Middle
Stem
Lower
Stem
Assembly (continued)

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Release
Clip
Battery
Compartment
Hand-grip
2-Way
Adjustable
Armrest
On/Off &
Volume
Switch
Menu
Button
Headphone
Jack
Settings
Switch
Dual-function
Trigger
switch S-Rod

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Mechanicals
BATTERIES
The PRO-ARC requires four AA batteries.
These non-rechargeable chemistries may be used: Alkaline, Nickel Oxy-Hydroxide
(Panasonic Oxyride or Duracel PowerPix), and lithium iron disulfide (Energizer L91), Nickel
metal hydride and nickel-cadmium rechargeable chemistries may also be used.
Zinc-carbon and so-called “heavy duty” batteries may not work, especially in cold weather. Do
not use these batteries.
Expect 40 hours of service in the field with one set of alkaline batteries. A rechargeable battery
kit is included with your PRO-ARC. Rechargeable batteries will usually deliver over 25 hours of
service without recharging, but when they start running low, they die suddenly with little warning.
Always install batteries which are of the same type and the same state of charge. Otherwise
battery life will be determined by the weakest battery, because the good batteries cannot
deliver their power with a dead battery blocking the current.
All 4 batteries are installed with the positive terminals facing upward.
The LCD screen shows battery condition on the right.

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Mechanicals (continued)
IMPORTANT: To avoid stressing the battery spring connection, install the batteries using this
technique:
1. Position the bottom (negative) side of the battery on top of the spring.
2. Do not install the top of the battery into the compartment yet.
3. Push down on the battery to compress the spring.
4. With the spring compressed a bit, then tip the
battery upright and push back into the
compartment.
1
2

PRO-ARC Comprehensive Operating Manual & Guide to Metal Detecting
Mechanicals (continued)
ARMREST
The armrest WIDTH and POSITION are both adjustable.
Armrest Width: The sides of the armrest can be bent
inward and outward. To best stabilize the detector to your
arm and body movement, squeeze the sides of the
armrest around your forearm. For a very secure fit, some
users prefer to bend the armrest in tightly against the
forearm such that you pry the sides loose each time you
place your arm into the armrest.
Armrest Position on Pole: Remove the two bolts to
position the armrest farther forward or back, to adapt to
your arm's length.
-- To reinsert the bolts, spin and twist them into place.
Be careful not to damage the power cable that runs
through the aluminum tube.
-- Insert both bolts completely through both sides of
the bracket before attaching the nut to the opposite
side.
-- After reinserting the bolts, tighten them very securely.
Adjust the armrest in or out
accordingly.
Adjust the armrest forward or back,
to adapt to your arm’s length.
16

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Mechanicals (continued)
You may need to use gloves for a firm grip. As you swing the detector from side-to-
side, you want the bolts tight enough so that you do not feel any movement between
the pole and armrest mounting bracket.
If you notice unwanted movement while swinging detector, check the tightness of the
locking collars. The locking collars must be rotated a full 270° to reach the locking position.
HEADPHONES
The PRO-ARC is equipped with a standard 1/4-inch stereo headphone jack at the rear of the
unit, located under the elbow as you hold the detector for use. Any headphone with a stereo
plug should work; headphones with a mono plug will not work. This device is to be used with
interconnecting cables/headphones shorter than three meters.
Using headphones (included) improves battery life, and prevents the sounds from annoying
bystanders. It also allows you to hear subtle changes in the sound more clearly, particularly if
searching in a noisy location. For safety reasons, do not use headphones near traffic or where
other dangers, like rattlesnakes, are present.

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Introduction to the Fisher PRO-ARC
HIGH PERFORMANCE The PRO-ARC is a multi-purpose high-performance computerized
metal detector. It has the high sensitivity and ground balancing control needed for all
types of environments, the discrimination responsiveness needed for target
concentrations under difficult conditions, and visual Target ID to facilitate searches for
specific types of artifacts. The PRO-ARC operates at 13 kHz for good sensitivity to both
high and low conductive artifacts such as gold and coins. The PRO-ARC comes with an
11-inch elliptical Bi-Axial searchcoil for maximum detection depth in mineralized soils.
USER COMFORT The PRO-ARC is among the lightest and best balanced of all high-
performance metal detectors, so you can hold and swing it almost effortlessly. The
armrest position is adjustable to fit your arm. The grip is durable high-friction foam
elastomer, comfortable in any kind of weather. The controls are conveniently located and
easy to learn how to use. Locking collars on the tubes eliminate rattling.
EASY-TO-USE & INFORMATIVE INTERFACE The entire menu is always visible on the LCD
display. The LCD display indicates the electrical signature (Target ID) of the detected
metal object. The display provides continuous information on battery condition and on
ground mineralization, which affects detection depth. Help messages are automatically
displayed on the bottom of the display when necessary.
LOW OPERATING COST The PRO-ARC is powered by four AA alkaline batteries, which will
typically last for more than 40 hours of use before needing replacement.

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Introduction to the Fisher PRO-ARC (continued)
DESIGNED BY THE INDUSTRY'S MOST TALENTED ENGINEERS The lead engineers on
the PRO-ARC design team were John Gardiner and David Johnson. David Johnson's
previous Fisher design credits include the CZ-platform, the Gold Bug-series, most of the
1200-series, Impulse Underwater Detector, CZ-20 Underwater Detector, FX3
magnetometer, the Gemini 2-box locator, the XLT-16 Acoustical Leak Detector and the
XLG-80 Ultrasonic Leak Detector. John and David were supported by fellow electrical
engineers Jorge Saad and Mark Krieger. The mechanical design was a collaboration
among David Johnson, Brad Fulghum, John Griffin and Tom Walsh.
MECHANICAL ENGINEERING
While the PRO-ARC is robustly engineered for outdoor use, it is not indestructible and it
is not waterproof.
RESET function
The PRO-ARC's microprocessor saves all settings which you input, even after the power
is turned off. If you wish to reset the settings to the factory preset, follow this process:
1. Turn detector off.
2. Press-and-hold the red MENU button and push-forward and hold the TOGGLE SWITCH.
3. Turn the detector on, while you are still holding the controls.
4. Release the MENU button and TOGGLE SWITCH.
5. See the F symbol. When the F disappears, the detector is reset.

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Controls
ON-OFF & VOLUME
Knob (Under the elbow)
This knob turns the
machine on or off, and
controls speaker volume
and headphone volume.
Manual knob position has
no affect on detector's
sensitivity or susceptibility
to noise from electrical
interference
On/Off &
Volume
Switch
Dual-function
Trigger switch
Settings
Knob Menu
Access
Tog gle From
bP or CL Process
DUAL FUNCTION
MENU BUTTON