Palmer Lmic User manual

Acoustic Listening Systems
Lmic, Gmic and Rmic
Operating Manual
Palmer Environmental
Ty Coch House
Llantarnam Park Way
Cwmbran
NP44 3AW
United Kingdom
Tel: +44 (0) 1633 489479
Fax: +44 (0) 1633 877857
Email: [email protected]
Web: www.palmer.co.uk
Acoustics Manual Issue 1 January 2003

1
Contents
Introduction and Scope ........................................................................................... 2
Guidance to Effective Acoustic Leak Detection .................................................... 3
Battery Warning........................................................................................................ 5
Lmic Acoustic Leak Sounding System .................................................................. 6
Preparing the Lmic for use...................................................................................... 7
Using the Lmic ......................................................................................................... 8
Lmic Technical specification .................................................................................. 9
Gmic Acoustic Leak Sounding System................................................................ 10
Gmic Controls ........................................................................................................ 12
Preparing the Gmic for use ................................................................................... 13
Using the Gmic....................................................................................................... 14
Gmic Technical Specification ............................................................................... 16
Rmic Acoustic Leak Sounding System ................................................................ 18
Microphone foot warning ...................................................................................... 19
Using the Rmic ....................................................................................................... 21
Rmic Technical Specification................................................................................ 22
Warranty.................................................................................................................. 24

2
Introduction and Scope
This manual covers the principles in acoustic leak detection for the following
products produced by Palmer Environmental.
Lmic (pronounced El Mike) Low cost leak sounding system
Gmic (pronounced Gee Mike) Ground microphone - leak sounding system
Rmic (pronounced Are Mike) Road microphone - leak sounding system.
The basics in the general operation are the same but each system has its own
advantages.
Lmic is designed as a low cost lightweight system which is simple to use yet highly
effective in the detection the sources of leak noise in industrial, commercial and even
household situations and can be used as a tool as part of a plumbing tool kit.
Gmic is a more sophisticated piece of equipment containing filters and the option of
aviation headphones. This combination provides the operator with a highly effective
listening device with the ability to virtually eliminate unwanted or interfering ambient
noise.
Rmic has the features of the Gmic but has the additional capability of being able to
use an acoustically shielded ground microphone foot for use in all weathers
especially high wind. The Rmic foot virtually eliminates the noise produced in bad
weather conditions and is especially suited for use on hard road surfaces, tarmac,
concrete etc.
The following section provides an introduction to the methods of acoustic leak
detection.

3
Guidance to Effective Acoustic Leak Detection
All acoustic leak detection methods are based on the premise that normal water
passage through pipelines takes place noiselessly. When the water passage is
disturbed a noise is created. Causes can include partial pipe blockages, sudden
changes in pipe diameter, abrupt changes in pipe direction, pumps or meters
installed in the pipeline, consumer usage or pipeline damage. Pipeline damage can
include holes, cracks or splits, complete pipeline rupture, leaking joints or leaking
valves.
Careful application of leak detection techniques will enable the operator to eliminate
detected noises generated by poor pipeline design or consumer usage and to
identify leakage due to pipe system damage.
The strength and clarity of noise generated by leaks will be affected by the water
pressure, the size and shape of the orifice allowing leakage, the type of ground
material around the pipeline, the type of ground cover over the pipe, the diameter,
wall thickness and material of the pipeline and the quantity of water leaking.
A small orifice or hole and high water pressure generally produces a higher
frequency noise. Often the noise level increases around valves, pipe elbows, T
connections, pipe ends, etc. since the partial obstruction increases pressure and
creates some further disturbance in the water path.
Leak noise is transmitted along the pipeline both through the water and the pipe wall
as well as into the ground around the pipe. The noise travels much better through
"hard" materials so that the noise travels much further along metallic pipes than
asbestos cement pipes which themselves are better than plastic pipes. Ground
material generally provides a poorer travel path than the pipeline itself. Soft sandy
ground provides a worse travel path than well compacted ground with a hard paved
surface covering.
The leak noise can change in strength and pitch as it travels along the pipe or
through the ground. The deeper the pipe is buried and the softer the ground the
more the noise will be dampened.
When a leak is produced in a metallic pipe the leak noise will transmit well through
the pipe. It does not travel so well through a plastic pipe. This means that a leak
noise can be heard further away on metal than on plastic. Also bear in mind that the
further you go from a leak noise source the more difficult it is to pinpoint that leak
noise accurately.
Background noise can interfere with leak detection. Traffic and machinery noises can
travel for considerable distances through both air and ground material and often
occur in the same frequency bands as leak noise. Sometimes it is necessary to use
leak detection techniques at night when interfering noises are less.
It is very important to adopt a methodical approach when using any instrument for
acoustic leak detection. It is necessary to practice the technique in order to
distinguish between different sounds, recognising background or interfering noises,

4
so that they can be eliminated. It is also essential that other (non-leakage) noise
sources such as consumer draw-off or partially closed valves are eliminated by
logical site inspection practices prior to any excavation taking place.
Hand probe
For normal soft ground surfaces the single pointed extension rod should be
connected - do not overtighten the screw thread. For direct contact with underground
fittings via access covers it may be necessary to use the second extension rod. To
do this remove the single rod and connect the extension rod - replacing the pointed
rod again. If the rods have been overtightened, spanner slots allow easy removal.
Surveying
The leak location can be narrowed down by listening at accessible contact points
such as meters, hydrants, valves and stop-taps, which provide points of good sound
pick-up particularly if the pipe is metallic. Use the hand-probe/extension rod to listen
at these points.
If there are no accessible contact points or if the pipe is of non-metallic material use
the microphone foot for listening, placing the foot over the pipe route in the area of
the suspected leak. Move along the pipe route listening at each accessible pipe-
fitting or at regular positions on the ground until you have identified the area of
maximum noise level.
Note: When you are listening on pipe-fittings the location of the point of maximum
noise will probably not indicate the leak position, only the fitting closest to the leak.
The noise level will also appear stronger where there is less thickness of ground or
other material for it to pass through. The leak noise will follow the path of least
resistance.
Pinpointing the leak position
Pinpointing the leak position involves a process of comparing a number of leak
noises. Select the most suitable sensor device; the microphone foot for hard ground
surfaces or the hand probe for soft ground.
Operate the ground microphone and adjust the headphone volume control to a
comfortable listening level. Once you have listened to the noise through the
headphones, switch off the amplifier (hand button on the Lmic or the headphones
button on Gmic/Rmic) and move the microphone foot or hand probe to the next test
position.
Repeat the sequence to listen to each of the test locations moving along the pipe
route in the direction where signal strength is increasing. If the leak noise level falls
you have passed the leak and should go back and reduce the distance that you
move between measurements. The loudest leak noise will then indicate the location
of the leak bearing in mind the ground conditions already mentioned.

5
Battery Warning
Gmic and Rmic
The batteries supplied and fitted to the Gmic and Rmic units are rechargeable lithium
ion. Do not short circuit or overcharge these batteries. Any misuse of these
batteries may result in explosion or fire. They must not be used in any other
application or used with any other equipment. Only batteries supplied by Palmer
Environmental must be used.
Lmic
The battery fitted to the Lmic is a rechargeable 9V PP3 Nickel Hydride battery. Any
replacement battery must be rechargeable and have the same specification.

6
Lmic Acoustic Leak Sounding System
The Lmic (pronounced “el mike“) is an easy-to-use, low cost, electronic listening stick
and ground microphone combined. It is ideal for general leak sounding operations
and can be fitted with either a tripod foot (for use as a ground microphone) or probe
rods (for sounding at fittings or in soft ground).
The control unit is hand-held with a “trigger” operation and a volume/sensitivity rotary
control. An LED indicates operation and battery status. It can be used to confirm
the position of underground leaks audibly from ground level; sound pipe fittings;
penetrate soft ground to listen for leaks or carry out traditional acoustic surveys.
Equipment list
1 Lmic hand held control unit
2 Microphone unit with cable
3 Tripod unit
4 2 probe rods
5 AC adapter
6 Headphones
7 Carry bag
8 Instruction manual
The Lmic equipment is shown here.
(Note the battery charger and
manual are not shown).
Lmic Controls
LED Rotary volume/sensitivity
control
Headphones /battery
charger connection
Trigger
switch
Microphone
connection
1
3
6
4
2
7
Bottom view of the Lmic showing the
trigger switch and the electrical
connections for the headphones/battery
charger and microphone.
Top view of the Lmic showing the rotary
control for volume and sensitivity.

7
Preparing the Lmic for use
The rechargeable 9v PP3 battery for the Lmic is supplied installed within the hand
control unit and will normally have only a nominal charge.
The battery will need charging either overnight (for up to 7 hours) to achieve full
charge before being ready to use.
Charging the Lmic batteries
Connect the charger lead to the rear connector of the Lmic and connect the charger
power lead to the 240V AC supply. The Lmic can then be charged overnight. An
optional accessory is the car cigarette lighter adapter that can also be used to
charge the batteries.
Battery replacement
Although these batteries are rechargeable they may eventually need to be replaced.
To do this, undo the two screws underneath the hand-held unit and separate the two
halves of the Lmic unit. Gently pull out the battery holder and replace the batteries.
When refitting the batteries and battery holder make sure no wires become trapped.
The Lmic connected to the universal 110-
240V AC charger

8
Using the Lmic
The Lmic is simple to operate. Select either the probe rods or the tripod unit and
screw into the microphone unit. (Use the tripod foot on hard ground and use the
probe rods on soft ground or when accessing water pipe fittings).
Connect the headphones to the rear connector and connect the microphone cable to
the forward connector. Put on the headphones and press the trigger button
underneath the hand-held unit to listen for leaks.
The volume/sensitivity can be adjusted using the rotary control.
LED indication
The green LED shows when the unit is operating and the red LED indicates low
battery power.
Care of the Lmic
The Lmic should be kept clean and dry and, where necessary, cleaned with a damp
cloth; abrasive materials must not be used.
The Lmic in use

9
Lmic Technical specification
Lmic hand held unit/sensor housing
Piezoelectric high sensitivity sensor mounted in PC-ABS (polycarbonate) housing
Single headphone/charger input socket with automatic sensing of device connected
Connectors
Amphenol military specification connectors for microphone and headphone/charger
connections
Charging
Universal 110-240V AC charger with 12V DC output
Car cigarette lighter adapter with 12V DC output (optional accessory)
Charge time: Overnight charge.
Microphone housing
High sensitivity piezo-electric sensor mounted in rubber housing with integral strain
relief
Low noise 0.75m cable (detachable)
Weight: 400g
Foot attachment
Cast metal tripod for ground contact
Hand probe attachment
2 stainless steel extension rods (each 400mm long)
Weight: 150g
Headphones
Lightweight high quality headphones
Impedance: 16 Ohms
LED
Green = normal operation
Red = low battery power
Optional accessories
•High specification aviation quality headphones
•Car cigarette lighter adapter with 12V DC output
•Acoustically shielded ground microphone foot, for use in all weather conditions

10
Gmic Acoustic Leak Sounding System
Introduction
The Gmic (pronounced Gee Mike) is a highly effective ground microphone. It
consists of a lightweight portable amplifier module, a set of mono headphones, and a
combination listening probe and ground microphone.
It is an effective electronic instrument for locating and pinpointing leaks from buried
water pipes.
Both visual and audible indications of signal strength (and consequent proximity) are
provided to enable operators to quickly and accurately confirm leak positions.
The control module is battery powered and provides up to 50 hours operational use
before a recharge is required.
Although the system is rugged and shower-proof (to IP65), it contains electronic
circuitry and should handled with care. The equipment should be kept dry and clean.
Where necessary it should be cleaned with a damp cloth; abrasive materials must
not be used.
Note: The headphones supplied with the Rmic cannot be interchanged. The
impedance of the headphones is matched to the Rmic control unit during
manufacture.
Key features
•Lightweight, easily portable system
•Excellent acoustic performance
•Easy to use control unit
•Membrane keypad
•Backlit multifunction LCD
•25 preset filter combinations
•Versatile – ground microphone and hand probe configurations
•Military specification connectors
•Robust construction for field use
•Rechargeable batteries (up to 50 hours use)
•Compact case containing full system

11
System Description
Control unit – robust for field conditions
The control unit is the operator interface. It is very easily portable, and can be
carried with either hand- or shoulder-strap. Its injection-moulded housings are
purpose-designed to provide long-term field durability and effective protection under
realistic site conditions. It is environmentally rated to IP65.
The control unit has a membrane keypad, with push-key operation, and a backlit,
multifunction LCD display. It interfaces to the headphones, charger and microphone
via military-specification connectors.
Versatile leak noise sensing
The acoustically shielded sensor mechanism provides isolation from airborne noise
interference and can be fitted with either a tripod foot (for use as a ground
microphone) or probe rods (for sounding at fittings or in soft ground).
Standard equipment list:-
1. Control/amplifier module with adjustable carry strap.
2. Combined hand probe and ground microphone with integral cable.
3. Two 400mm stainless steel rods.
4. One short legged tripod.
5. Mono headphones.
6. Lithium ion battery pack Battery charger.
7. Carry case.

12
Battery
life
indicator
Signal
strength
Headphone
volume
indicator
High pass
filter
selector
buttons
On / Off
and
LCD
backlight
Low pass
filters
selection
buttons
Headphone
volume control
On / Off
Headphone
button
LCD
dis
p
la
y
Gmic Controls
The Gmic is simple to operate and has a limited number of controls.
Controls and functions of the Gmic base unit
Headphone and combined
charger socket
Sensor socket

13
Preparing the Gmic for use
The battery pack for the Gmic is supplied as a separate item in the carry case. The
batteries within this pack are supplied quarter charged. To insert the battery pack
into the Gmic unscrew the three screws underneath the unit, remove the cover and
packing foam and connect the battery pack, place in the battery compartment, refit
the packing foam, and then replace the cover with the three screws.
Battery charging
To charge the batteries, connect the charge lead from the charger to the
Headphones / Battery charge connector on the back of the Gmic. Plug the charger
unit into the mains supply.
While the batteries are charging, the charging LED will be illuminated. This only
goes out when the batteries are fully charged. The Gmic unit cannot be used while
the batteries are charging. The time required to charge the batteries from flat is
approximately 7 hours, which can be easily achieved overnight.
The On/Off switch can be pressed while the unit is on charge to see how much
charge is in the batteries at any time. However, the Gmic MUST be switched back
off again in order to resume charging.
When the unit is switched on the battery power available is indicated by three LCD
blocks.
When all three blocks are illuminated, the batteries are fully charged.
When two blocks are illuminated, this indicates normal usage.
When only one block is illuminated, this indicates the battery is low on charge.
When the single block starts flashing, this indicates that the batteries are very low
and should be recharged as soon as possible.
Battery replacement
Although the batteries are rechargeable, they may eventually need to be replaced.
Only batteries configured to the correct specification and type must be used. These
are available from Palmer Environmental.
To replace the batteries, first switch the unit off. Unscrew the three screws
underneath the unit, remove the packing foam, then unplug the battery pack
connector releasing the batteries. Connect a new battery pack, place in the battery
compartment, refit the packing foam, and then replace the cover with the three
screws. The batteries will need charging

14
Using the Gmic
Select the sensor attachment required, (the steel rod(s) or the tripod), and screw this
into the bottom of the microphone housing. Plug the headphones into the Gmic.
Gmic Switch On/Off.
Switch the unit on by momentarily pressing the On/Off switch. The unit will switch on
and remain switched on until this same button is pressed again unless it is left
unused. The Gmic will switch itself off after 30 minutes of inactivity.
To switch the unit off, the On/off switch must be pressed and held down for a few
seconds.
Headphones switch On/Off
The headphones can used switched on in two different modes.
a. Latch mode. Momentarily press the Headphones On/off button. The
headphones will switch on and remain switched on until the
Headphones On/Off button is pressed again.
b. Momentary mode. Press and hold down the Headphones On/Off
button. The headphones will remain switched on for as long as the
button is pressed. As soon as the button is released, the headphones
will switch off.

15
Filter selection
To clarify the leak noise, background or unwanted noise frequencies can be filtered
out using the High Pass and Low Pass filter buttons. To filter out low frequencies,
use the High Pass buttons as shown below.
High pass filter settings
High Pass filter
Press once to increment the filters at 30Hz intervals. This will only allow frequencies
above each selection to pass through. All frequencies below this are blocked.
Press once for 30Hz
Press twice for 60Hz
Press three times for 90Hz
Press four times for 120Hz.
The high pass filters have these four settings only.
To reduce the filter setting, press the left hand button.
Low pass filter settings
The low pass filter settings work in a similar way but with the ranges listed below.
The highest frequency that can be passed through the unit is 3kHz.
To reduce the frequencies passed…
Press the left low-pass filter button once for 2kHz
Press twice for 1.5kHz
Press three times for 700Hz and
Press four times for 300Hz
The minimum band pass is 120 - 300Hz
There are a total of 25 combinations of selectable filter settings.
Back light
To view the LCD display in bad light, illuminate the backlight by pressing the
combined On/Off Backlight switch briefly. This then latches the backlight in an on-
position. Note, the backlight automatically switches off after 1 minute to conserve
battery power.
Press the same button again to re-illuminate the backlight.
To switch it off, press this same button momentarily.
Low
pass
filter
High
pass
filter

16
Gmic Technical Specification
Control Unit
Low power analogue design with active digitally switched filters
2 x 16 character LCD display with backlight control
LCD numerical display of:
·Signal level display 0 – 99
·Headphone volume control
·Filter settings (25 possible)
·Battery level
Filter Options
·High Pass - 20, 30, 60, 120Hz
·Low Pass – 300, 700, 1500, 2000Hz
·All Pass – 0-3000Hz
·Band Pass – Any combination of the above High / Low settings (25 total)
Power supply
2 x Lithium ion 1.8Ah rechargeable batteries giving up to 50 hours operation without
backlight (minimum 35 hours with backlight)
Amphenol connectors for microphone and headphone/charger connections
Environmental rating IP65
Membrane keypad with push-button control
Dimensions 206mm x 167mm x 86mm
Weight 1kg
Charging Universal 110-240V AC mains charger with 12V DC output
Charge time 8 hours

17
Microphone Housing
High sensitivity piezo-electric sensor mounted in rubber housing with integral strain
relief
Low noise 1.5m cable (detachable)
Weight 500g
Foot Attachment
Cast metal tripod for ground contact
Hand Probe Attachment
2 stainless steel extension rods (each 400mm in length)
Combined weight of rods 162g
Headphones
Lightweight robust high fidelity headphones
Scope of supply
•
Control unit
•
Microphone unit with lead
•
Tripod foot
•
2 probe rods
•
AC adapter
•
Headphones
•
Carry strap
•
Transit case
•
Instruction manual

18
Rmic Acoustic Leak Sounding System
Introduction
The Rmic (pronounced R Mike) is a highly effective ground microphone for all
weather conditions. It consists of a lightweight portable amplifier module, as used in
the Gmic system, a set of mono headphones, and a ground microphone housed
within an acoustically shielded foot.
It is an effective electronic instrument to confirm the position of underground leaks
audibly from ground level.
Audible indications of signal strength (and consequent proximity) are provided to
enable operators to quickly and accurately confirm leak positions.
The control module is battery powered and provides up to 50 hours operational use
before a recharge is required.
Although the system is rugged and shower-proof (to IP65), it contains electronic
circuitry and should handled with care. The equipment should be kept dry and clean.
Where necessary it should be cleaned with a damp cloth; abrasive materials must
not be used.
Optional extras include standard aviation quality headphones and a hand held probe
for sounding fittings.
Note: The headphones supplied with the Rmic cannot be interchanged. The
impedance of the headphones is matched to the Rmic control unit during
manufacture.
Key features
•Lightweight, easily portable system
•Excellent acoustic performance
•Easy to use control unit
•Membrane keypad
•Backlit multifunction LCD
•25 preset filter combinations
•Versatile – ground microphone and optional hand probe configurations
•Military specification connectors
•Robust construction for field use
•Rechargeable batteries (up to 50 hours use)
•Compact case containing full system
•Optional aviation quality headphones

19
Microphone foot warning
The Microphone foot has a sensor attached that can be seen from the bottom of the
unit. Users must not attempt to unscrew this sensor as this will break internal
components of the microphone resulting in irreparable internal damage.
Sensor replacement is then the only option.
Any necessary repair or dismantling of the foot must be carried out by Palmer
Environmental or by an authorised distributor.
Sensor:
Do NOT attempt to unscrew.
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