AKA T72 User manual

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AKA T72
OPERATING MANUAL
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GENERAL INFORMATION-----------------------------------------------------------------------------------------------2
GENERAL DESCRIPTION OF THE DEVICE---------------------------------------------------------------------------2
PACKAGE CONTENTS------------------------------------------------------------------------------------------------------3
TECHNICAL SPECIFICATIONS---------------------------------------------------------------------------------------------3
GETTING STARTED----------------------------------------------------------------------------------------------------------4
POWER SUPPLY----------------------------------------------------------------------------------------------------------------4
CONTROLS AND CONNECTIONS ---------------------------------------------------------------------------------------5
DISPLAY SCREEN--------------------------------------------------------------------------------------------------------------7
SENSITIVITY CT, PB SENSITIVITY / CT VOLUME----------------------------------------------------------------7
GROUND BALANCE--------------------------------------------------------------------------------------------------------8
DISCRIMINATION SEARCH MODE AND SETUP-------------------------------------------------------------------11
SEARCH MODE “ ALL METAL “----------------------------------------------------------------------------------------12
DYNAMIC AND STATIC MODES OF OPERATION------------------------------------------------------------------13
MODE “TURBO”-------------------------------------------------------------------------------------------------------------14
MODE “ECONOMY”--------------------------------------------------------------------------------------------------------15
MODE S ALGORITHM------------------------------------------------------------------------------------------------------15
MULTI-FREQUENCY-------------------------------------------------------------------------------------------------------15
PARAMETER MENU--------------------------------------------------------------------------------------------------------16
ADDITIONAL MENU (ADD. MENU)-------------------------------------------------------------------------------------20
USER PROGRAMS----------------------------------------------------------------------------------------------------------21
USING THE HODOGRAPH FOR IDENTIFICATION --------------------------------------------------------------22
SEARCHCOIL REPLACEMENT -----------------------------------------------------------------------------------------23
SEARCH AND IDENTIFICATION METHODS -----------------------------------------------------------------------24
SEARCHING FOR LARGE/ FLAT NON FERROUS TARGETS WITH A HIGH VDI ANGLE ----------------------------27
EXAMPLES OF SOME COMMON TARGET VDI’s-----------------------------------------------------------------28
WARRANTY INFORMATION ----------------------------------------------------------------------------------------------29

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GENERAL INFORMATION
Metal detector T.72 is designed to search for and identify metal objects in the dielectric (dry sand,
wood, etc.) and low conducting media (soil, brick walls, etc.). Some applications of use are Criminal;
Engineering; Housing and community services, construction and fire-fighters to search for
underground utilities, pipelines, cables, manhole wells etc...Archaeology and treasure search. The
device is designed to operate under the following conditions: Ambient temperature from -20 up to
+50°c (-4 to 122 F); Relative humidity up to 98 per cent at temperature of 25°c (77 F); Atmospheric
pressure from 630 to 800 mm Hg.
GENERAL DESCRIPTION
The T.72 is an eddy current selective metal detector that works on the principle of induction balance.
The main distinguishing feature of this model is the use of its original software and hardware. Our
multi-frequency technology (MFT) allows the use of any search coils manufactured by us, regardless
of their operating frequency (Hz). That is, the device itself will make adjustments and calibrate to the
selected coil. The device uses the original technology of signal processing sensor-technology space
and harmonic filtering (SFT), minimizing the hindering effect of ferrous soil (salinity) and, thereby,
increasing the reliability of the identification of deep and small objects.
Basic search mode – Dynamic search mode, i.e. detection of an object occurs with constant motion
of the search coil.
To pinpoint the exact location of the detected object the device has a static mode of operation
(Pinpoint).
The device has 2 methods for identifying the object detected:
-Audio programmable multi-mode,
-Visual (Hodograph, VDI value, rating (level) signal-RS).
The device has two independent search channels: RT and ST.
The RT channel (real time) works in real time, i.e. sound indication is given simultaneously with the
movement of the search coil over the object. Sound indication in this channel is a single-tone signal,
volume and frequency of which can change when an object approaches the search coil. Also using
the duration of the tone we can get an estimate of size of the target detected.
When the received signal from an object exceeds the specified RT threshold, the channel generates
the ST audio or short tone.
Channel ST (short tone) is the audio identification channel for the type of object detected. When the
received signal exceeds the threshold of the RT channel the detector issues a short audio tone (ST),
and the screen displays the hodograph (vector time curve) of the detected object.
The frequency of the short tone indicates the type of object detected (high tones – non ferrous
metal, low tone - ferrous metal). The number of tones can be specified by the user (the default is 4
tones).

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Each channel has an independent adjustment of its sensitivity. The sensitivity of the RT and the
sensitivity of ST.
The RT channel has a higher sensitivity than the ST channel and its main objective is to locate the
object and alert the operator that there is something there.
The T.72 is equipped with mode (Turbo). This is a high coil current mode, which is used to improve
response from good signals at depth.
There are also 4 custom user programs.
The detector is equipped with a manual or automatic ground balance system with the ability to
adjust auto track rate (APB).
PACKAGE CONTENTS
• The electronic unit with a telescopic pole 1 ea.
• Search coil - eddy current transducer (ECT) 1 ea.
• Magazine for 6 batteries (type AA)* 1 ea.
• Operators Manual 1 ea.
• Headphones** 1 ea.
• Carrying Bag** 1 ea.
*) batteries sold separately
**) purchased separately or as an option.
TECHNICAL SPECIFICATIONS
The maximum detection range of metal objects
(air test with coil Ø260mm DD) via RT:
• 25 mm dia. coin - 60 см (23.5 in);
• Helmet - 150 см (59 in);
Display modes:
• Audio, 5 modes (RT, RT-M, RT-ST, RTL-ST, STP);
• visual (LCD display with a resolution of 128x64 pixels).
Search modes:
• All metals;
• sectored discrimination with 2 ° step.

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Control modes:
• Dynamic programmable;
• Static with adjustable threshold.
Power Supply: - 6 batteries (type AA (LR6));
Continuous operation time: - 16-18 hours in normal mode, 6-7 hours in Turbo mode
(Rechargeable batteries 2500 mAh) - up to 40 hours in economy mode
Overall dimensions, mm:
• Telescopic rod - 1200 (Max.);
• Electronic unit - 120х70х115;
• Search coils - Ø 260 mm, Ø 380 mm, 150x260 mm, 240x320 mm
Weight of the device: - 1300 g (without battery)
The device allows the ability to work in water depths of up to 15 meters, without submerging the
control box.
GETTING STARTED
Assemble the metal detector. To do this: install the appliance in a metal bar; tighten the Collet
Chuck; install the inner (plastic rod) sensor; install the rod with the sensor in a metal bar to desired
length, using the tabs and holes in the rod tightly and evenly wrap the sensor cable around the rod.
Freely hanging cables can Cause falsing; connect the sensor connector to the electronic unit.
WARNING! Do not over tighten the attachments and fittings for the telescopic shaft. This applies in
particular to the plastic bolt for the search coil and shaft collets. Thanks to a specially designed three-
knee construction shafts do not need to be disassembled for transportation, simply push the knee
shafts into each other all the way and the device is ready to be carried compactly (fig. 1)
POWER SUPPLY
The device is powered using 6 AA batteries or 6 rechargeable NIMH. Rechargeable batteries and
charger are not included and must be purchased separately. We recommend that you use NiMH
batteries from SANYO, ANSMANN 2500 capacity-VARTA or 2850 Ma/h. The use of standard alkaline
batteries is possible but not cost effective as the rechargeable batteries pay off after 4-5 recharges.
When using batteries, with a capacity of 2500 Ma/h, continuous operation is approximately 16 hours
in the main mode and 6-7 hours in Turbo mode. Several recommendations on the use of nickel-metal
hydride batteries:
-Avoid fully discharging the batteries with each cycle use as this shortens their lifespan. Slight
"memory effect" is eliminated by one complete discharge approximately once a month.

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-After extended periods, of storing the device, it is usually good practice to fully discharge and charge
the batteries a total of 4-5 times.
-Remember that due to the self-discharge nature of the batter capacity falls (by About 5% per day, so
it is advisable to charge batteries before each use.
-DO NOT use rechargeable batteries that have different capacities in the same set.
WARNING! When connecting the battery magazine to the device connector insure the battery is
properly connected (polarity is indicated on the battery cartridge) and insure the voltage source is
correct. In the case of incorrect polarity or improper voltage the device can be damaged
CONTROLS AND CONNECTIONS
On the rear panel of the device are the coil connector, on/off switch and the serial number of the
device.

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Located on the front panel are the LCD graphic display (with a resolution of 128 x 64 dots) and 11
touchpad controls.
ST SENS : Sets the sensitivity of the ST (short tone) channel
RT SENS : Sets the sensitivity of the threshold RT channel (Real Time)
SOUND : Sets the volume of the audio
DISC : Select the Discrimination edit mode
AM / mode : Switch between all metals/discrimination
- / TURBO : Navigate through the menu and change the settings, also turns the Turbo mode on/off.
+ / ALGO : Move through the menu and change the settings, as well as turn on/off the S Algorithm
PROG : Switches between User Programs
GROUND : Access the Ground Balance modes
OK : Confirms the selected settings. Selects a menu item. In search mode switches between Static
and dynamic (Pinpoint) modes. In ground balance mode switches between Auto and Manual GB.
MENU : Button to enter the Main Menu

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DISPLAY SCREEN
In search mode the display device displays the Hodograph information of detected objects and
information about the current operation modes.
VDI-number “Visual Discrimination Indication”. This is the index of electrical conductivity of the
object or the angle between the vertical axis and the predominant direction of the hodograph (time
curve). In this case, hodographs which are on the left side of the screen have a negative VDI, and the
right - have a positive VDI number. The amplitude of the signal, from detected objects, is displayed in
standard numerical units
ST SENSITIVITY, RT SENSITIVITY / VOLUME
This section introduces the three main parameters that you'll use most often. For each of these
settings there is an individual button on the control panel.
ST SENS [1 .. 14]. Increasing this setting allows you to increase the depth of targets you're searching
for, but it reduces the accuracy of identification and increases the risk of false positives. The
recommended value is 9-10. Warning! Setting of the ST sensitivity above 11, and especially 14 can
lead to a significant increase in the amount of false positives from the soil in high salinity or when
bumping the search coil.
RT SENS [0 .. 9]. Adjusts the sensitivity of the threshold or RT channel you hear constantly during the
search. The value of this parameter is set as a compromise between sensitivity and comfort.
Increasing this value increases sensitivity in the threshold channel. However this can reduce the
comfort in searching. Recommended settings are 6-7.
VOLUME [1 .. 9]. This setting adjusts the overall volume of the audio response from detected objects.
Select the value based upon individual comfort preference. The current values of these parameters
are displayed on the screen above the relative buttons. To change any of these settings press the
appropriate button. The value of the selected option is highlighted on the screen with a rectangle
around the appropriate value. Press the button - or + to set the required value. In order to exit the
parameters simply click the button again. When neither the RT, ST or Volume values are displayed on
screen - the buttons + and - will now act as on / off modes for the Turbo and S-algorithm, (see below)

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GROUND BALANCE
Balancing the device to the ground is the single most important part of the device settings for
accurate search results. Improper ground balancing can result in decreased responses to targets and
may result in instability as well as an increase in false ground signals.
To explain the basic physics behind the ground balance procedure. Every object has its own shape,
conductivity and magnetic component, which together are called the VDI (Visual Digital Index).
Remember that the VDI is the angular response that is numerically equal to the angle of deflection of
the signal vector time curve (hodograph display) on the vertical axis. The soil, or ground, depending
on the degree of mineralization (presence of iron oxides) imposes its signal on the target signal thus
changing the VDI upscale. This is especially true on small or deep targets, as well as large highly
conductive targets (copper, silver, aluminum). This can actually push these high VDI targets up and
over into the high negative VDI range known as “VDI wrap around”. To minimize this effect, it is
crucial to perform a proper and accurate ground balance procedure.
The basic objectives of balancing:
1. Make the soil 'invisible' to the instrument, i.e. exclude false signals from the ground where there is
no target.
2. Install the correct (standardized) reference system number for the VDI. When receiving a signal
from both the ground and a detected object the detector must subtract mathematically the signal
from the ground in order to display a correct VDI indication of the detected target
Keep in mind that when performing “air tests” inside after the detector has been previously balanced
in soil may result in incorrect VDI readings. This is due to the correction factor for the VDI previously
set in the last ground balance. This may result in the loss or “invisibility” of large aluminum, silver and
copper targets. If the ground setting is too positive the VDI will be offset positive and vice versa if the
ground balance is negative.
This may also lead to targets air testing as iron, as well as a false increase in sensitivity when air
testing. Remember that for every 1 degree of ground balance offset from the 0 or neutral point we
get a corresponding increase or decrease in the VDI scale for a given target. IE a 1 degree+ ground
balance will increase the VDI by +1.
For example, if you are air testing a large copper coin that would normally give a VDI of +82 to +84
but is now air testing with a VDI of -86. The result is that the device ground balance is set +10 to +12
degrees too positive for performing an accurate air test.
Balancing with a piece of ferrite is required before performing an "air test" of the device. Put the
device on a non-metal surface, turn on automatic ground balance mode, count to three, then bring
the ferrite to the center surface of the coil from a distance of 25-30 cm (10”to12”) to complete the
balancing procedure. Puzzled? Let's make it easier: Take a CD and pass it flatwise in front of the
search coil.
If the CD gives a vertical hodograph and VDI of 0 (+1 or -1), then the device is ready for “air" tests.

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If the VDI of the CD differs from these values, then in auto GB click OK (to enter manual GB) and
adjust the phase of the ground balance in the desired direction. When the VDI of the CD is at 0 (+1 or
– 1) your device is ready for air testing.
BALANCING PROCEDURE.
We would like to bring your attention to the automatic balancing procedure developed by
experienced users.
1. Find a metal-free area. You can find it by the threshold tone response in RT mode. On an
unbalanced device there will be a response to the clean ground, however the sound will be soft and
"diffused", without a strong localization. While the sound would be sharp and with a strong increase
in sound above a metal object. Select an area with no localized sharp threshold tone increase while
swinging the search coil 5-10 cm to the left and to the right above the ground. If there is no localized
sharp threshold tone increase then the area is suitable for balancing.
2. Having found the metal-free area, raise the coil 30-40 cm above the ground press GROUND wait
for 3 seconds, and move the coil to the ground smoothly but not too slow.
Warning! Do not move the coil to the ground closer than 10% of the search coil diameter (for the
searchcoilØ26 cm – 2-3 cm). This is related to the change in the pattern of the search coils physical
interaction with the ground in what is called the "Close Zone" and it may impact balancing accuracy
resulting in false responses in clean areas with high levels of sensitivity.
A short tone (Hum) means the completed balancing procedure. If there is no tone or it does not
sound during lowering, but sounds when moving up, repeat the procedure with the same formula:
30-40 cm above the ground, 3 seconds, and then lower the coil to the ground. Follow the ground
vector on the screen during the process. Its shape should be a strait, slightly trembling line, on the
horizontal axis of the ground scale.
If it makes sharp angles or is “chaotic” on the screen, this means that you are trying to balance near a
metal object in the ground. In this case, the device may perform a ground balance, however it will be
incorrect and you will notice multiple false signals from the ground. If this occurs, simply re-balance
the detector in an area clear of any metal targets.
Once you have chosen a clean location to balance the detector and have done so, note the value in
the lower left hand corner of the ground balance screen. Now, should you chose to ground balance
again later on and there is a sharp difference between this value now, as compared to the previous
ground balance, there is good reason to suspect that there was metal close by and you will need to
ground balance again.
If the coil all the same was a metal object, giving an automatic balance (items with VDI close to 0, e.g.
foil), the device will give two consecutive tones, similar in tone to that of iron in the search mode,
while at the same time the screen will display an exclamation point within a triangle. Accordingly,
you will need to ground balance again on a clean spot of land.
After balancing, in the lower left corner of the screen will display a numerical value of balance
(phase), this is the amount by which the device will adjust the VDI, excluding the effect of the soil.

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In the right corner of the screen it should be noted that the average phase angle ground balance is
different for each instance of the device and can also depend on the technological variability in
parameters of the coil and the ambient temperature.
However do not forget that your device remains in the automatic balancing mode and at any
moment may deem it was time to rebalance to your shovel, boots, or hunting partner. If you want to
review the results and values of the current automatic ground balance procedure press OK to enter
manual mode and disable automatic balancing. In the upper right corner of the screen will appear M
instead of the letter A. To exit the ground balancing, click GROUND on the instrument panel.
Switching between modes is as simple as performing successive clicks of GROUND. While in the
manual balance mode by pressing - or + one is able to adjust
the ground balance in the proper direction. Bob the coil vertically above the ground (rising to 20 -
30cm / dropping by 3-5cm), making sure that the vector of the soil is along the horizontal axis and
that the hum is gone when raising or lowering the coil.
When working on the ground with uneven salinity, such as arable land, it is not always possible to
accurately ground balance the unit in automatic mode. This can be due to the uneven or lumpy
nature of the soil. This can sometimes leads to false responses from the identification channel. In this
situation the phase of the ground balance can vary by more than 3 degrees. If you encounter this
problem then perform the ground balance procedure as follows.
Find a clean patch of ground with a width of 60 centimeters. Switch to manual ground balance and
making short horizontal search sweeps with a width of 50cm at a height 3-5cm above the ground,
you will see a straight line on the ground the screen (if the line jumps, then there is metal present). In
this case, if the balance is wrong, you will hear a buzz from the soil and the soil line on the on the
screen will not be horizontal.
Press + and - until the line is horizontal and the buzz disappears. Your device is fine-tuned to the
ground. For a small increase in the depth of the identification of large silver and copper coins (kettles,
basins and other large pieces of highly conductive metals) it is possible, after performing automatic
ground balancing, to enter the manual balance mode and set the GB point from -1 to -2 from the
automatic GB reference point.