Discrimination Mode. Fisher Research Labs F75 SPECIAL EDITION

F75-MANUAL(122811).qx 12/14/12 9:04 AM Page 19

F75

Comprehensive Operating Manual & Guide to Metal Detecting

LCD Visual Display (continued)

BATTERY CONDITION INDICATOR

Fresh alkaline batteries will illuminate all three bars. When no bars are displayed and the batteries are about to go dead, the BATT legend will start flashing. The detector should operate for an additional 30 minutes from the time the BATT legend starts flashing. If using NiMH rechargeable batteries, the display will remain stuck on the second or third bar for most of the battery life; when it drops to the first bar, the batteries will go dead within several minutes.

G.B.

This is the ground balance setting, 0-99. It is displayed when in the Manual G.B. menu setting, or when the trigger is pushed for FASTGRAB computer-assisted ground balancing.

SETTING

This is illuminated when you are in the menu. When the word “SETTING” is indicated, the number being displayed is a setting, and not, for instance, a Target ID indication.

MESSAGES

The small rectangular box at the bottom-center of the LCD displays advisory messages.

If a metal object or highly magnetic soil is so close to the searchcoil that the signal is overloading the circuit, the message OVERLOAD - RAISE COIL will appear.

Such overloads will not harm the detector, but the detector will not detect metals properly under these conditions. Raise the coil until the message disappears; the siren sound will also stop. Resume normal detection.

The message RAISE COIL only appears when using the bc process, accessed through the

PROCESS # menu selection. This message indicates the presence of a target which may be too close to the searchcoil to be accurately identified. For better target identification, sweep the searchcoil farther away from the surface of the ground.

The message PUMP COIL TO GB will appear when you push the trigger forward to ground balance. See the Ground Balance section of this manual for instructions.

The message CAN’T GB can only appear when the trigger is pushed forward, invoking

FASTGRAB automatic ground balancing. This message appears when the detector is unable to measure the soil in a manner suitable for ground balancing. This message is usually the result of the presence of metal. Try another spot to find an area free of metal.

BACK LIGHT

The LCD is back-lighted for use in low light and dark conditions.

The backlight is always illuminated, but the illumination is usually not evident in daylight.

You cannot turn the backlight off. The single high-efficiency light emitting diode providing the illumination is a low current device, and has a negligible impact on battery life.

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F75


Discrimination Mode

The Discrimination Mode is used to eliminate trash metal objects from detection, e.g. nails, aluminum foil, or pull-tabs. The searchcoil must be in motion for metal objects to be detected.

Discrimination incurs some loss of sensitivity to small or deep objects.

The F75 discrimination system is much improved over conventional discrimination systems, and may function quite differently than other discriminators you may be accustomed to. In older systems, the apparent sensitivity decreases as discrimination level increases. The F75’s sensitivity may increase as discrimination increases, depending on the process number and notches being used. Therefore, do not use the discriminator to control sensitivity. First set the discrimination level and notches to establish objects to detect or eliminate; then adjust sensitivity downward to eliminate interference, or upward to “work into the noise,” if preferred.

SENSITIVITY

This controls the signal gain, and is adjustable from 1 to 99. Unlike the All Metal modes, the

Discrimination mode is designed to operate silently. If you hear noise when there is no metal present or when the searchcoil is not in motion, reduce the Sensitivity setting until the machine goes quiet. NOTE: There is no interaction between the sensitivity settings of the All Metal and Discrimination Modes.

The sensitivity system has two stages, 1-29 (low gain), and 30-99 (high gain). As you lower sensitivity and cross the transition from 30 to 29, you may notice the background noise

increase. You may need to adjust to a setting of 29 or less to silence electrical interference, or to prevent overload on highly mineralized ground or in salt water. You may also notice a shift in the ground balance setting over difficult ground conditions as you cross this transition.

DISCRIMINATION LEVEL

This is adjustable from 0 to 65, and controls the range of objects to be eliminated from detection (discriminated out or rejected). Objects with numeric values below the selected discrimination level will not be detected. NOTE: The numerical range that pertains to each class of object is printed at the top of the visual display. To eliminate iron, a setting of 15 is usually about right. A setting of 65 will eliminate aluminum trash and zinc pennies, but nickels will also be lost, unless you notch-in nickels with the NOTCH feature.

To use DISC LEVEL

1. Highlight DISC LEVEL using the MENU button.

2. Rotate the SETTINGS knob.

As you rotate the knob, a number between 0 and 65 appears.

3. Press MENU when you reach the desired target discrimination value.

• If you do not press MENU, and let the display time-out, the last displayed value will be stored as the discrimination value.

• All targets, up to and including the value selected, will be eliminated from detection, unless notched-in.

5. A slash will appear over the target words being eliminated. Notice that two slashes can appear over each word. The left slash represents the bottom half of the range; the right slash represents the top half of the range. When you select a value within any range, the slash will appear, even though all values within that range might not be

eliminated from detection. To recall the discrimination setting, press the MENU button until you enter the DISC LEVEL feature.

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F75


Discrimination Mode (continued)

NOTCH

Unlike Discrimination Level, which eliminates all targets from the left of the scale to the right,

NOTCH can eliminate and re-include targets within the scale displayed at the top of the display. Inclusion or exclusion of target ranges is indicated with a half-crossed or crossed icon.

To demonstrate how to set a notch, follow this instruction at first use.

1. Reset all detector values to default: a. turn detector off b. press-and-hold red MENU button and push-forward-and-hold Toggle Switch c. turn detector on while continuing to hold MENU and Toggle d. release Menu and Toggle.

2. Press MENU button 4 times to move down to the NOTCH feature

-then rotate the SETTINGS knob to the right until the number 40 appears.

-then press MENU again to accept this notch value.

3. Notice that a thin line appears across the word “TAB” printed on the top of the display.

4. Press MENU again to exit the NOTCH feature.

5. Targets in the first 1/2 of the TAB range (TAB range is from 36 to 55) will be eliminated from detection.

6. A half-slash will be permanently displayed across the top-left of the word “TAB.”

NOTCH allows you to select target ranges equal to 1/2 of each category for inclusion or exclusion from detection. As you rotate the knob, the target indicator will appear above the range currently selected. If you set the notch value anywhere within the range, the notch value will not necessarily stop at this number, notch ranges are fixed as follows:

1. 1-7 iron

2. 8-15 iron

3. 16-20 foil

6. 31-35 nickel

7. 36-45 tab

8. 46-55 tab

4. 21-25 foil 9. 56-60 zinc

5. 26-30 nickel 10. 61-65 zinc

The following are characteristics of NOTCH programming:

• As you rotate the knob to enter a notch range, the target indicator block at the top edge of the screen illuminates to show you the range you are in.

• After you have selected a notch, a slash is illuminated over that range, indicating that all targets within that range (see chart above) are eliminated from detection.

• When you enter the program to make a change to the notch settings, you are

changing the status of the notch. If no slash is illuminated and you press MENU to set a notch range, you will be notching-out this range. If a slash was previously illuminated and you press MENU to set this notch range, you will be notching-in this range.

• Programming a notch range always reverses the status of the notch.

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F75


LCD Visual Display (continued)

Since different metal objects can produce similar signals, and since minerals in the soil can distort the signals, the probable target ID's are just that -- probable. There is no way of knowing for sure what's buried other than to dig it up. Experienced metal detector users have a rule of thumb -- "when in doubt, dig".

DEPTH

When the trigger is pulled to facilitate pinpointing an object, the 2-digit numerical display indicates the approximate depth of the object, in inches, based on the assumption that the object is a typical U.S. coin. Small objects will read deeper than they actually are, and large objects will usually read shallower than they actually are.

The DEPTH bar graph on the left of the display divides target depth into shallow, medium, and deep. This depth range appears while searching, and is less accurate than the value derived using the pinpoint toggle switch.

Bar graph ranges for a coin-sized object are Shallow (0-4inches), Medium (4-8inches), and

Deep (8inches +).

CONF (Target Confidence Indicator)

This 6-segment graphic indicates how confident the detector is of the 2-digit target identification it has assigned. If all 6 segments are displayed, you can be confident that the target ID is accurate. If 3 or fewer segments are displayed, the confidence is very low.

Junk targets tend to produce lower confidence indications than coin targets of similar electrical conductivity. Sloppy sweep technique also reduces the confidence indication. You can use this indicator to train yourself to sweep more skillfully.

Fe

3

O

4

BAR GRAPH (magnetite)

This bar graph displays the magnetic mineralization factor, or magnetic susceptibility, of the soil.

Magnetic susceptibility is expressed in terms of the percent volume of the iron mineral magnetite, which most black sand is made of. The depth to which objects can be accurately identified is strongly influenced by the magnetic susceptibility of the soil. High Fe

3

O

4 values have a greater effect on detection depth in the Discrimination mode than in the All Metal mode. For the most accurate Fe

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4 reading, pump the searchcoil as though you were ground balancing.

Fe

3

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4 approx.

Range micro-cgs Description

3 7,500 uncommon but not rare, heavy mineralization

1 2,500 heavy mineralization, not uncommon in goldfields

0.3 750 heavy mineralization, but not uncommon in some regions

0.1 250 medium mineralization, typical

0.03 75 light mineralization, but common

0.01 25 light mineralization, your G. B setting may also be low blank <14 quartz & coral white beach sands

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F75


LCD Visual Display

In normal operation, when the searchcoil passes over a metal object, the electrical signature

(2-digit I.D.) of the metal object is displayed on the numeric display for 4 seconds, unless superceded by another detected object. On a given buried object, the number will bounce around if the signal is weak or if the amount of ground mineralization is high.

At the top of the display, a block illuminates to indicate the classification of the object.

Target ID is provided in all three modes, and requires motion in all modes, including STAT.

NUMERIC TARGET I.D. (2-digits)

The following table shows the numbers typically associated with certain commonly encountered nonferrous metal objects. Older silver U.S. coins usually read about the same as their modern clad equivalents. Modern quarter-sized dollar coins like the Susan B. Anthony and the Sacagawea read about the same as a quarter. Many Canadian coins are minted from a magnetic nickel alloy which gives very inconsistent readings and may register as iron. Most one-ounce silver bullion coins will fall into the same range as the modern U.S. $1 Eagle.

OBJECT

Most iron objects foil from gum wrapper

U.S. nickel (5¢ coin) aluminum pull-tab aluminum screwcap zinc penny (dated after 1982) aluminum soda pop can copper penny, clad dime

U.S. quarter (25¢ coin), clad

50¢ coin, modern clad old silver dollar coin

US silver Eagle $1 coin

TARGET I.D.

4-12

16-25 typically 30

33-55

60 - 70 typically 60 most often 63-69, but can vary widely typically 70 typically 80 typically 86 typically 90 typically 91

PROBABLE TARGET I.D.

The probable target ID zones at the top of the LCD display represent the signal ranges produced by various coins and types of metal objects. When a metal target is detected, the microcomputer analyzes the signal and categorizes it based on what kinds of metal objects usually produce that kind of signal. The microprocessor then displays a rectangle-like icon along the top of the LCD screen above the corresponding category.

For instance, if the detected signal fits within the parameters usually exhibited by zinc pennies, the microcomputer will categorize the signal as "zinc penny". The LCD screen will then illuminate the block above “ZINC”

Copper pennies (pre-1982) will usually register in the DIME zone.

Most gold jewelry is small, and will tend to read in the 16-55 range. Silver jewelry usually has more metal in it and therefore tends to produce higher readings.

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F75



Using DISC LEVEL in conjunction with NOTCH gives you a great deal of flexibility in deciding which values to include or exclude from detection. Beware that this combination can be confusing.

Here are some examples of NOTCH used in conjunction with DISC LEVEL

If Discrimination Level is set at 60, and you set the top-of-foil (21-25) notch between 21 and 25, then: top-of-foil range (21-25) is NOTCHED-IN (i.e. detected)

If Discrimination Level is set at 23, and you set the top-of-foil (21-25) notch between 21 and 25, then: 21, 22, & 23 are NOTCHED-IN. 24 & 25 are NOTCHED-OUT

If Discrimination Level is set at 15, and you set the top-of-foil (21-25) notch between 21 and 25, then: 21-25 are NOTCHED-OUT

NUMBER OF TONES (# OF TONES)

This menu selection allows you to select the number of audio tones emitted by the detector.

Different search conditions, search objectives, or personal preference will determine how many tones you want to hear. With the below settings, you can decide to hear the same tone, regardless of the target category, or have different categories of targets induce different tones.

The “# OF TONES” selections are:

1: SINGLE MEDIUM PITCH TONE.

All types of metal induce the same tone.

1F: MEDIUM-TO-HIGH PITCH TONE varying in proportion to target signal strength.

Large shallow objects will produce a squeal. The variable audio pitch provides you more information about the detected object, but some people find the sound on strong signals too annoying.

2F: TWO TONES.

Similar to 1F, except that iron produces a low-pitched tone regardless signal strength.

Useful if you want to hear all targets and want to identify iron. Most relic hunters prefer this selection.

3H: same as 3, except that nickels produce a high tone.

3: THREE DIFFERENT AUDIO TONES. Iron produces a low pitch tone. Aluminum trash, zinc pennies, and nickels produce a medium tone. High conductivity coins produce a high tone. The 3-tone selection is often preferred for coinshooting. Most users will set the discrimination level below nickels, at about 25, and dig only objects that produce a consistent and repeatable high tone. NOTE: with this setting, steel bottle caps may produce consistent high tones, similar to coins. See Capabilities & Limitations section for advice on identifying steel bottle caps.

4H: same as 4, except that nickels produce a high tone.

Useful when coinshooting in a trashy area.

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F75



4: FOUR DIFFERENT AUDIO TONES This selection is similar to 3, but with a fourth mediumhigh tone for targets in the numeric range of 53 to 65. This four-tone system is useful for searching in areas where there may be very old coins which register in this range.

dP: DELTA PITCH This setting produces a tone whose pitch varies in relation to the visual ID number -- the higher the ID, the higher the pitch. Good for relic hunting. This setting is also useful in areas with a high concentration of steel bottle caps. Coins will produce a fairly constant pitch as you sweep back and forth. Bottle caps produce inconsistent tones, often with a squawk at the beginning of the sound.

Process Number (Process #)

This menu selection offers the user a choice among several different methods of audio discrimination to accommodate a variety of search conditions and personal preferences.

These methods differ in the way the signals are processed for analysis.

The Process Number selections are:

dE: DEFAULT PROCESS

This is the best process to use for most conditions, and is thus the default.

JE: JEWELRY PROCESS

Detector will be more sensitive to small and low-conductivity metals like jewelry, but will run noisier in trashy areas.

bc: BOTTLE CAP MODE

Response is modified so that steel bottle caps will usually produce inconsistent, or nonrepeatable, tones and broken sounds. There may be a slight reduction in the ability to separate adjacent targets. Use this process in areas with a high concentration of steel bottle caps. Also refer to the Capabilities & Limitations section for sweep techniques to aid in the identification of steel bottle caps

PF: for use in plowed fields.

Some users may prefer this process for hunting in irregular ground, especially plowed fields.

WHAT YOU SEE VS. WHAT YOU HEAR

The visual target ID displayed on the LCD is based entirely on sampled processing; the number displayed represents a snapshot of the target’s identification as the searchcoil passes over the object. When using these different processes, or methods, the detector’s audible response may differ from the visual. When using the different processes, there is not a 100% correspondence between what you see and what you hear, especially on buried targets where ground minerals influence target ID and audible response. By making the audio and visual systems independent, the F75 allows each system to do what it does best. The audio is optimized for quick response and target feel, whereas the visual system provides the best numeric resolution of target ID.

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PinPoint Feature

After a buried target has been located using the All Metal or Discrimination modes, you want to pinpoint the exact location of the target in order to facilitate its recovery. Accurate target pinpointing will minimize digging.

F75

Activate the PinPoint feature by pulling the trigger switch located under the housing. Unlike the motion All Metal and Discrimination modes, PinPoint does not require motion to detect metal. PinPoint will detect objects while the coil is in motion and will continue to detect metal if searchcoil motion stops over the target.

Ground Pick-Up

If you have not performed the ground balancing procedure, the PinPoint feature usually causes the ground to sound off. This means that while pulling the pinpoint trigger, the audio tone will get louder as you lower the searchcoil to the ground; this is called ground pick-up.

Since you want to hear the target, rather than the ground, we recommend first ground balancing in order to eliminate ground pick-up. Alternatively, if you experience ground pick-up, you may place the coil very close to the ground, off to the side of the target; then pull the trigger, and raise the searchcoil slightly while passing it over the target.

How to Pinpoint

Position the searchcoil an inch or two (2.5-5cm) above the ground, and to the side of the target. Then pull the trigger. Now move the searchcoil slowly across the target, and the sound will indicate the target’s location. As you sweep from side to side, and hear no sound at the ends of the sweep, the target is located in the middle of that zone, where the sound is loudest and the audio pitch is highest. If the sound is loud over a wide area, the buried object is large.

Use the PinPoint feature to trace an outline of such large objects.

Narrow It Down

To further narrow the field of detection, position the searchcoil near the center of the response pattern (but not at the exact center), release the trigger, and then pull it again.

Now you will only hear a response when the searchcoil is right over the top of the target.

Repeat this procedure to narrow the zone even further. Each time you repeat the procedure, the field of detection will narrow further.

Buy a Pinpointer

When you kneel down to unearth the desired object, you may find it frustrating as the object may appear exactly like the surrounding soil. You may hold the object in your hand, and find it necessary to pass a handful of dirt over the searchcoil to see if it contains metal. An easier way is to use a handheld pinpointer. It is a probe-like device which is poked into the ground, making close up pinpointing a snap, reducing digging time, and minimizing the size of the holes you will dig. Fisher Research Labs offers the FPoint™ pinpointer, a robust and inexpensive device designed for this purpose.

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Discrimination Mode. Fisher Research Labs F75 SPECIAL EDITION

Discrimination Mode

LCD Visual Display

PinPoint Feature

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Discrimination Mode. Fisher Research Labs F75 SPECIAL EDITION