JW Fishers RMD-1 Operation Manual

Remote Metal Detector

OPERATION MANUAL

RMD-1

012511

JW FISHERS MFG INC

1953 COUNTY ST.

E. TAUNTON, MA 02718 USA

[phone]; [phone]; FAX [phone]

Email: [e-mail] WEB: www.jwfishers.com

LEFT BLANK

Coil Set

Underwater

Electronics

Housing

Control Box

Mounting Arms

RMD-1 System

SPECIFICATIONS

Sensitivity (in water or air): High Position

• Piece of eight......................................................... 10 in.

• Shotgun ................................................................. 28 in.

• 4" diameter pipe .................................................... 34 in.

• One gallon can ...................................................... 36 in.

• 2' x 4' sheet metal.................................................. 50 in.

• Maximum range..................................................... 62 in.

PERFORMANCE/DESCRIPTION:

• Detection area (standard coil) ...............62 in. deep, 52 in. wide

• Input voltage .......................... 9 -36 vdc, or 120 vac, or 220 vac

• Power consumption.............................................................. 8 w

• Readout ................................................................. Meter, Audio

DIMENSIONS/WEIGHT: Air/Fresh water

• Coil set ............................... 10" x 16" x 5" H ................ 32/2 oz.

• U/W Housing & elect. ....... 9 1/2" L x 2 1/2"Dia..1.4 lbs/4 oz pos

electronics alone............1 7/8" x 7" x 1 1/2" H.................. 5 oz.

• Surface Control Box .........13"L x 13"W x 6"H............... 7.6 lbs.

• Cable ............................. 1/4" Dia x 150-1000' ..........4-25 lbs.

• Shipping Box ................... 29"L x 25"D x 15"H ..........25-61 lbs.

MATERIALS/COLOR:

• Underwater housing ............................ High impact PVC/yellow

• Control Box . High impact Underwater Kinetics case, PVC/black

• Cable ................................................. 4 conductor PVC/chrome

• Coil set ........................................... High impact urethane/black

OPTIONS

• Up to 1000 ft. cable.

• RS232 computer output on downstairs electronics.

• Analog output on downstairs electronics (0 to 2.5 or 0 to 5 vdc).

• RS232 computer output with GPS on surface control box.

• Analog output on surface control box (0 to 2.5 or 0 to 5 vdc).

• Input voltage for control box 220 vac and 9-36vdc.

• Different coil sizes (special build).

SENSITIVITY (switch selectable):

i

MAINTENANCE

Your RMD-1 was designed to be maintenance free. It is constructed
of corrosive resistant materials. It is recommended the coil be
rinsed in fresh water after use. It is recommended the control box
be kept out of direct sunlight and away from moisture. Close the lid
when not in use, control box is not water proof. Keep cable
connectors dry. Please write/phone the factory at [phone],
[phone], or E-mail [e-mail] if any problems.

LIMITED WARRANTY

Your detector underwent constant inspection during assembly to
insure many years of trouble free performance. The RMD-1 has a
TWO FULL YEAR warranty from the date of purchase. During this
period, your detector will be repaired free of charge should a failure
occur due to materials or workmanship. The Warranty does not
cover broken cables or coils, or damage due to dropping or general
misuse.

Should service be required, write/phone us explaining the nature of
the problem, and we will supply shipping instructions. All repairs are
made at our factory. Repairs by unauthorized persons may void the
Warranty.

15

GPS OPTION (used with RS232 Control Box option)
The GPS option allows the boat's GPS to be connected to the
Control Box. This option is used with the RS232 Control Box option
which will then output the boat's GPS and the RMD's output signal
to a computer.

Attach the output cable from the GPS system to the RMD-1
Control Box.
NOTE: The GPS system must have a serial output, not USB.
There is no adaptor to connect a GPS with USB output to a serial
port.

If the data cable for your GPS has a 9 pin “D” connector on the
end (for a PC serial port), it will connect directly to the “GPS
INPUT” jack on the Control Box. If the data cable for your GPS
has bare wire leads on the end, you will need to splice the
appropriate wires to the cable shown below. If your GPS did not
come with a data cable, one can be obtained from the GPS
retailer or manufacturer. There are usually a variety of cables
available, many also include connections for an external power
source for the GPS. We recommend using an external power
source as using the GPS with the data output consumes a set of
small batteries in a few hours.

INTRODUCTION

The RMD-1 is a high performance Pulse Induction metal detector
which can be attached to almost any ROV or towed underwater
system. Pulse induction technology allows the RMD-1 to detect both
ferrous and non-ferrous metal objects under the ocean floor while
ignoring mineralization in the salt water and seabed. The ROV metal
detector locates and tracks underwater pipelines, finds missing
tools and dredge parts, locates weapons and unexploded ordnance,
and finds lost treasure.

Pulse detectors have had a major impact on the salvage business.
Their major claim to fame is that they are very sensitive and do not
detect minerals (extreme concentrations of iron ore may give a
modest reading). This lack of mineral detection is an answered
prayer for salt water divers who have to contend with heavy miner­alized deposits on the ocean floor which produce false readings on
conventional detectors. Pulse detectors ignore these mineral de­posits and respond only to metal targets (ferrous and non-ferrous
metal).

HOW PULSE DETECTORS WORK

Pulse detectors operate by transmitting a continuous stream of high
energy magnetic pulses (one hundred per second), from the Coil.
After each pulse is transmitted, the unit then "listens" using the Coil
as the receiving antenna.

Coil

Figure 1

When a transmitted pulse hits a metal object, a magnetic field is
induced in the object. This causes eddy currents to flow in the metal,
which in turn generates a second magnetic field. This field is picked
up by the Coil, amplified, and then displayed by the meter and heard

in the speaker/earphone.

1

PULSE

COIL

NOTE: The transmitted
pulse covers a much
larger area than shown
above.

EDDY CURRENTS

COIL COIL

RECEIVE

target

14

Coil Coil

Coil

GPS DATA CABLE

red wire for Signal (Data Out)

black wire for Return (Data
Ground)

To RMD-1 Control Box

SOLDER WIRES TO
GPS DATA CABLE

pin 1

123

4

5

Enlarged front view of 5 pin
connector . Pin 2,3 and 5
not used.(PIN END)

fish 1 white

ground

black + shield

pin 4

Analog output (0-5vdc)

Pin 2,3, and 5 Not used

2

13

4

5

5 pin socket
in box

5 pin DIN
Connector
in RMD-1
Control Box

REMOTE METAL DETECTOR DESCRIPTION

The RMD-1 system employs two coils molded into rugged ABS
shells and firmly attached to the underwater vehicle with a corrosive­proof tubular PVC frame. The frame provides a sturdy mount and
keeps the coils far enough away from the ROV so as not to be
affected by the metal parts. The oval coils produce a detection
envelope which extends 3 to 5 feet into the bottom. The sleek, low
profile coil design minimizes drag and weight on the ROV.

When the coil senses metal it sends a signal to the RMD-1
"downstairs" electronics unit attached to the underwater vehicle.
This downstairs electronics unit can produce RS232 output , O-5 vdc
output, or a proprietary signal used by the JWF topside control/
readout unit. The output from the downstairs electronics unit can
be transmitted through the ROV's umbilical or a separate cable.

The standard RMD-1 has a topside Control Box which displays the
readout with both a meter and audio alarm. The closer the proximity
of the metal target, the stronger the reading. The topside unit can use
the underwater vehicle's umbilical cable to supply voltage to the
downstairs electronics unit and to receive the output signal from the
downstairs unit. The RMD-1 can be powered from 120 vac (stan­dard) or 220 vac, or 9 - 36 vdc.

The RMD-1 is easy to operate and readily attaches to most any
underwater vehicle.

COIL SIZES
The detection range of a pulse metal detector is determined to some
degree by the coil size. Larger coils will detect large targets deeper,
but have less sensitivity to the smaller targets. The 10 in x 16 in x 5
in coil, which is standard on the RMD-1, is an ideal size for detecting
both small targets, such as individual coin size objects, and larger
targets to 5 ft deep. Special coil sizes can be built for special
applications.

ANALOG OUTPUT OPTION
The analog output option allows the RMD-1 to be connected to an
external device such as a strip chart recorder or data logger. The
output is 0 to +5.00vdc. The voltage is a representation of the
detection signal strength.

The analog output uses 2 wires and is wired to a 5 pin DIN connector
on the RMD-1 as Follows:

RS232 WIRING

J W FISHERS MFG

INC

BERKLEY, MA 02779

65 ANTH ONY ST

VISUAL DETECTION DISPLAY

POWER

AUDIO

J W FISHERS MFG

INC

BERKLEY, MA 02779

65 ANTH ON Y ST

VISUAL DETECTION DISPLAY

POWER

AUDIO

2

13

5 pin DIN
Connector
in RMD-1
Control Box

RS232
White
Black and Shield

RS232
Interface
9 pin "D"
female
connector

pin 2
pin 5

Pins 2,4 and 5 Not used

5 pin socket
in box

1

2

3

45

3
Enlarged front view
of 3 pin connector
(PIN END)

1

2

5

2

END VIEW

GPS OPTION (used with RS232 Control Box option)
The GPS option allows the boat's GPS to be connected to the
Control Box. This option is used with the RS232 Control Box option
which will then output the boat's GPS and the RMD's output signal
to a computer.

GAL CAN

36 in

MAX RANGE

62 in

DRAWN
TO SCALE

MAX DETECTION ENVELOPE

(10 in x 16 in x 5 in COIL)

52 in

30 in

RMD-1 SENSITIVITY
The sensitivity of the RMD-1 is switch selectable. Normal operation
is in the Hi position. If you are trying to pinpoint a target but the meter
goes to full scale, switch to Low or Med sensitivity. The target is
directly below the center of the coil when the meter is at its highest
point (but not full scale). When operating in Low sensitivity, you can
expect detection ranges about one half of Hi. You can expect these
detection ranges whether the target is buried under mud, coral,
sand, or rocks.

Sensitivity (in water or air): Hi Position

• Piece of eight......................................................... 10 in.

• Shotgun ................................................................. 28 in.

• 4" diameter pipe .................................................... 34 in.

• One gallon can ...................................................... 36 in.

• 2' x 4' sheet metal.................................................. 50 in.

• Maximum range..................................................... 62 in.

RMD-1 DETECTION ENVELOPE
The detection envelope for the RMD-1 is very large - much larger
than the coil width/length. The drawing below shows the detection
envelopes (Hi position) for a one gallon can and for the maximum
detection envelope (a very large object).

When using the RMD-1 with a GPS receiver the following connection
and power-up sequence must be followed for proper operation.

1. Cable up entire system including GPS/Loran C to RMD-1,
RMD-1 to the computer (RS232 interface), and RMD-1
downstairs to RMD-1 control box. Also connect all compo­nents to their proper power sources.

2. Power-up GPS/Loran C and obtain current position fix.

3. Power-up computer.

4. Power-up RMD-1

5. Initiate data collection program on computer.

If the RMD-1 is powered up before the GPS has obtained the current
position or the GPS interface cable is disconnected, the RS232
interface will default to the "No Position Available" message as shown
above.

If the GPS/Loran C loses its position fix during operation, the RMD­1 will default to the "No Position Available" message".

If either of these conditions occur correct the fault (re-initialize the
GPS, check connections, check battery condition). Once the GPS/
Loran C is again functioning properly, power down the RMD-1, wait
five seconds and power up the RMD-1. The position information
should now be present.

RS232 ON DOWNSTAIRS ELECTRONICS OPTION
With the RS-232 option, the downstairs electronics can be connected
to any computer or data recorder equipped with an RS-232 input. The
specification of the interface is as follows: 8 bit ASCII data, 4800 baud
rate (custom baud rates are available), 1 stop bit and no parity bit.

The message relays the signal strength from the RMD expressed
from 0 to 5,000 millivolt (0 to 5.000 volts). The complete message is
repeated continuously with no delay between messages.

The message sent on the RS-232 output is as follows:
(Note: The message length can vary as shown)
RMD=95mv<cr><lf>
RMD=3270mv<cr><lf>

RMD=5000mv<cr><lf>

•The baseline reading (no metal present) is approximately 100mv.

See page 9 for connection information.

3

12

RS232 /GPS OPTION
With the RS232 option the RMD-1 Control Box can be connected to
any computer or data recorder equipped with an RS232 input. The
specification of the interface is as follows: 8 bit, 4800 baud rate, 1
stop bit, and no parity bit.

The GPS/Loran C interface allows the ships position information to
be input into the RMD-1. The RMD-1 then reformats the information,
combines it with the signal strength reading from the search coil, and
sends it to an external computer via the RS232 interface.

Any GPS or Loran C receiver equipped with a NMEA 0183 output
can be used with the RMD-1. If you are not sure if your receiver has
NMEA 0183 output, check its manual or call the manufacturer. You
may find that you have to tell your GPS receiver to send out the 0183
information (refer to your GPS manual). If given a choice, select
0183A or 0183C format. Both versions include the latitude/longitude
message format called GLL. The RMD-1 can also receive the
message format called GGA, if the message GLL is not available.
The RMD-1 automatically checks for the presence of either mes­sage on power-up.

The sample message sent on the RS232 interface is as follows:
Position 4151.745353, N, 07102.394576, W <cr>
RMD= 3270mv <cr> <cr>.

Where the "Position" is the latitude and longitude coordinates from
the GPS or Loran C receiver and "RMD" is the detection signal
strengths expressed from 0 to 5,000 millivolts (0 to 5.000 volts). The
complete message is repeated once per second.

If a GPS or Loran C is not being used, or if the GPS or Loran C
message is not being properly received by the RMD-1, the message
will be as follows:

NO POSITION AVAILABLE <cr>
RMD = 3270mv <cr> <cr>.

4

UNDERWATER HOUSING:

Contains downstairs electronics board.

Can be powered from surface Control

Box (standard) or from local ROV power

( 9-36 vdc at 8 w). Electronics board can

be removed from housing and mounted

in ROV. Electronics board output is

RS232, or analog, or a proprietary sig-

nal to surface Control Box (standard).

SURFACE CONTROL BOX:

Contains switches and controls

for operating the system. When

metal is detected by the coil, the

meter in the Control Box swings

up and the audio alarm sounds

off. Control Box also has an op-

tional RS232 and analog output

for computer or chart recorder

connection. System can be op-

erated without the Control Box

by applying power directly to the

underwater housing.

J W FISHERS MFG

INC

BERKLEY, MA 02779

65 ANTH ONY ST

VISUAL DETECTION DISPLAY

POWER

AUDIO

Underwater

Housing

Up to a 1,000 foot of cable

Surface Control

Box

OutPut

(RS232 or Analog)

Input Power

(120/240 vac

or 9-36 vdc)

2 or 4 wires

RMD-1 SYSTEM CONFIGURATION

CABLE:

Can use umbilical cable from

ROV or a separate cable. A 4

wire cable is required if power

to the U/W housing electron-

ics is from the surface; 2

wires if power is from ROV.

COIL:

High noise immunity coil

set. Standard coil set is 10"

x 16" x 5". Larger coils are

available by special order.

Full ocean depth coils are

also available.

4 foot cable

standard

RMD-1 CONTROL BOX
The heart of the system is the control box which contains all controls
and indicators for the system:

• Meter Indicates the presence of metal by swing­ing to the right. The closer the metal is to
the coil, the further it will go to the right.

• Speaker When the meter moves past .2 , the
speaker sounds off. The higher the meter
goes, the higher the pitch (frequency) out
of the speaker.

• Volume Control Adjusts the volume out of the speaker or
earphone.

• Earphone Jack Accepts a standard 1/4" earphone plug
(stereo or mono). Speaker output is si­lenced when earphones are plugged in.

• RS232 Output With this option the RMD-1 can be con­nected to any computer or data recorder
with a RS232 input.

MOUNTING AND CALIBRATION
The RMD-1 has been factory calibrated for proper operation when mounted on a
JW Fishers ROV or other non-metallic host platform. In other applications, the
search coils should be mounted as far from metallic components as possible. Only
nylon or 316 stainless steel fasteners may be used near the search coils.

Before permanently mounting the search coils, test the RMD system to insure that
it will operate properly with the search coils in the chosen location. When testing,
the host platform and search coils must be clear of other metals (at least 6 ft from
the search coils). To check for proper operation, test each sensitivity setting (low,
medium, and high). In each setting, the zero adjust knob should be able to set the
meter between 1 and 2, the normal operating range. If using the RS232 output, the
reading should be close to +0.1vdc (+100mv dc).

If the above condition can not be met, try repositioning the search coils for the
lowest meter reading. Once the best location is found, secure the search coils in
the chosen position. Retest the system. If the zero adjust knob cannot zero the
meter in each sensitivity setting, complete the following procedure to calibrate the
downstairs board.

Equipment needed: Phillips screw driver, small flat blade screwdriver, DC volt
meter able to read down to 0.1 vdc. If the RS 232 output will be used, the readings
from this test may be observed on the PC display instead of the dc volt meter.

1) Remove the (2) 4-40 x 3/8" flat head screws from the underwater housing.

2) Slide the cable end out of the housing.

3) Rest the circuit board on a non-metallic surface. Do not unplug any cables.

4) Turn on the RMD system.

5) Measure the voltage on the right pad of J2. Connect the (-) lead of the meter to
pin 2 of JP6 (green wire).

6) Turn the trimpot R37 with the small flat blade screwdriver. Turn in the direction
that causes the voltmeter reading to decrease. DO NOT ADJUST ANY
OTHER TRIMPOTS

7) Adjust R37 until the voltmeter or PC display reads +0.10vdc (+100mv).

8) Test the RMD system again. The zero adjust knob should be able to zero the
meter in all sensitivity switch positions. Slowly approach the search coils from
below the 'Bottom Coil' with a metal object. The voltage should begin to
increase as the object is brought closer to the 'Bottom Coil'. Please note that
the detection envelope is non-linear. The voltage change will be very small
(50-100mv) when the object is at the outer edge of the detection envelope.
The voltage change will be greater as the object is brought closer to the search
coils.

9) Reinstall the underwater housing and o-ring. Be sure the o-ring and its seats
are clean. Reinstall the (2) 4-40 x 3/8" flat head screws. Do not overtighten.

10

5

Power Cord

Speaker

Volume Control

Earphone Jack

Analog Output (option)

or

GPS Input (if RS232 option)

RS232 Output

(option)

Coil

Selection

Switch

Zero Adjust

Power On LED

Power Switch

Meter

• GPS Input If the RS232 output option is selected then
this connector is used to input GPS data
from your GPS. It is then outputted with the
RS232 data string.

or

• Analog Output With this option a 0-2.5 vdc (or 0-5 vdc)
voltage is provided. This output tracks the
meter movement.

• Cable Jack The cable from the "downstairs electronics
unit" plugs into this jack.

• On/Off Switch Turns power (24vdc) on in the system.

• Power on LED Lights when power is on.

• Sensitivity Switch A three position switch which selects the
sensitivity of the detector:

Low Pos. The unit is operating in LOW sensitivity

(about 1/2 of HI).

Med Pos. The unit is operating in MED sensitivity

(about 2/3 of HI).

Hi Pos. The unit is operating on HI sensitivity (nor-

mal operating mode).

9 6

RMD-1 DOWNSTAIRS BOARD CONNECTIONS

RMD-1 DOWNSTAIRS ELECTRONICS

1

2

1

2

Bottom Coil

Top Coil

JP5

JP4

Blk

Yellow

Blk

Green

R33

R10

R16

PS1

1

2

4

3

5

1

2

Output

JP6

Green

White

R37

R56

U6

System Disable

JP1

1

2

J1

J4

J2

J3

JP7

60 Hz

50 Hz

9-36 vdc input

1

2

Black

Red

JP-1 SYSTEM DISABLE JP-4 TOP COIL JP-6 OUTPUT

1. (+) 1. (+) 1. Signal

2. Signal Return 2. GND 2. GND
JP-3 DC POWER INPUT (9-36 vdc) JP-5 BOTTOM COIL JP-7 FILTER JUMPER

1. (+) 1. GND or SD COMMAND

2. (-) 2. (+)

LEFT BLANK

OPERATION/CHECKOUT

- Position the coil outside and 5-6' away from any metal.

- Plug the cable from the underwater electronics board into the
control box.

- Connect power to the system.

- Turn the control box Power Switch on and note that the POWER
ON LED is illuminated.

- Turn the Sensitivity Switch to HI position.

- Turn the ZERO ADJUST knob until meter reads approximately .1.

- The system is ready to go. Periodic adjustment of the Zero Adjust
knob may be necessary.

DETECTING METAL
As metal passes below the lower Coil, the needle swings up. At
about a .2 meter reading the audio sounds off and increases in pitch
(frequency) as the needle swings higher. Maximum meter swing
occurs when the target is directly below the center of the Coil. As you
go past the target, the needle returns to .1 and the audio stops.

Run some tests out of the water with a metal target (gal can is fine)
to get the feel of the detection pattern. There is no need to move the
coil, simply move the target around (below) the coil set.

The upper coil is the noise cancellation coil. As metal is brought
above this coil it causes the meter to go down. If metal is brought
from the side of the coil set, the top coil cancels out the detection of
the bottom coil. This feature allows the coil set to be located near a
metal object with out detecting it. However, if the metal is too close
to the side of the coil it will reduce sensitivity to other targets. It is
when a metal object passes below the plane of the lower coil that the
target is detected.

7

8