Aka Signum MFT 7272M version 100c User Manual

							ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 21 
Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.  
 
  
Zoom WS (Zoom weak signals) [1:2/1:4/1:7]. This option was designed to increase 
the capabilities of visual hodographic identification. It allows to increase sizes of weak signal 
hodographs as well as to evaluate the signal level by the size of the hodographic picture. For 
instance,  setting to  the 1:2 scale  you  can  increase  and  thoroughly  examine  a  low-signal 
hodograph.  Scaling  1:7  you  can  evaluate  signal  levels  in  a  wider  range  by  the  size  of  the 
picture respectively.  
SOUND SETTINGS  Sound Mode [RT/RT-M/RTL-ST/RT-ST/ST-P} T h e r e are 5 types of sound modes. 
 
RT [Real Time}.  In this mode the audio output is in sync with the movement of the 
coil.  As  the  coil  approaches  the  target  the  audio  rises  and  as  it  leaves  the  audio  falls 
respectively. This type of display allows for a maximum depth of detection without any type 
of  audio of  the  type  of  the  object  (all targets of a  single tone).  Real-Time  is  used  when  you 
want to search for deep targets, for example to search for military items. 
                 RT-M [Real time-Multifrequency] This is a single channel (RT) search mode with 
tone or audio ID. This differs from other audio ID modes in that the ST channel is not used. 
We can think of this as Threshold tone ID. Audio response is in real time while searching and 
can provide more target information than may be available in the ST modes especially under 
certain target rich environments. The number of tones can be set in “No. of tones”, and may 
be set from 2 to 4.  RT-ST [Real-Time - Short tone]. This is the preferred sound setting. 
Sound indication of the object occurs in 2 stages. Real time sound appears first (RT) with a 
medium tone, and then, after the object is identified the RT threshold tone is replaced by 
the ST tone of an appropriate frequency. The duration of the tone can be changed using the 
Duration ST. RTL-ST [Real time before the threshold - Short tone]. Along with RT-ST this is the other main type of sound indication. Different from the RT-ST this setting is 
characterized by the fact that when the ST tone is generated the RT tone drops out. This 
setting will help with audio overload to the user when detecting in trash or in areas with 
many targets. ST-P {Short Tone Polyphonic} Ability to give both a low tone and high tones  
at the same time. For example, when giving a signal from the small flat iron targets (beer 
bottle caps, small pieces of sheet metal, etc.). Num. of tones   [2,  3,  4,  5].  Sets the number of tones for audio identification.  LT Boundary (The boundary for the low tone (iron)) This option allows the user to set the boundary for the low tone. In areas of mineralized soil as well as areas with small 
iron nails, targets such as small shallow gold and other low VDI targets will indicate a 
negative VDI. Usually these give a signal between the medium-large iron VDI range and foil 
VDI range. These will not fall completely within the range of iron but also not quite at the 
range of foil. For example medium wrought iron targets such as wrought iron nails will have 
a VDI vector of -45 to -40.  Foil will have a VDI vector of 0 or close to this. Therefore those 
targets with a VDI from 0 to -35 are considered “suspicious” and subject to research when 
looking for small gold jewelry, small medieval daggers or coins within debris.  When setting 
the boundary of the LT remember these facts in order to not miss valuable targets when 
searching under these conditions. So, if we receive a good tone, even if the hodograph 
indicates a loop, with 95% confidence we can say that this is possibly a good non ferrous 
target. Together with the separation rate of the MM search mode this setting will increase 
your chances of not missing a non ferrous target mixed in the iron. Try to set the border for  
 
  
						

							22 ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 
Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.  
 
 
 
these lower tones appropriately. If you perform a search in places where the medium/large 
iron can be interesting (Arrowheads, knives, medieval items etc.) you can move the non-
ferrous tone to the sector border where the majority of large iron indicates at -45 (-50 
possible maximum). 
 Volume WS [Volume of weak signals 1-9] A d j u s t i n g this parameter  allows  you  to  change  the  volume of  the ST  from weak  signals  from  small  or  deep 
targets. Smaller values of this parameter can control the level of the volume signal for a 
wider  range  of  target  depths. However, at  very  low  settings signals  from  small  or 
extremely  deep  objects  can  be  too  quiet. Very  high  settings  will  reduce  the  differential 
volume level between  deep and shallow targets. Therefore, the value of this parameter 
is selected experimentally, to individual user preferences. 
                  Volume  LT  [1..9].  Parameter  adjusts  the  volume  of  targets  within  the  setting  of 
the LT border (iron). Sometimes it is useful to reduce the volume or even mute the sound 
from iron in order to make the search more comfortable.  This parameter value is selected 
based  on  the  personal  preference  of  the  user.  The  value  of  Fe-9  Volume  adjusts  the 
volume levels of iron and non-ferrous objects.                 In the case of overloading the electronic circuit due to large or shallow targets under the coil the device will issue an audible and visual alarm overload.      
 
 
ADDITIONAL MENU (ADD. Menu) 
The  menu  is  in  addition  to the  main options  menu,  this  sub-menu  extends  the 
capabilities  of  the  sound  and  the  display options as  well  as an  option  to adjust  the auto-
tuning of the balance to the soil. 
To enter the sub-menu, press and hold down              Navigate the sub menu  
 
options by using the buttons             and              Selecting a menu item and enter the 
 
 submenu by pressing the button             Navigate  the parameters of the selected sub-menu  
 
by the buttons             and              to select an option use the button.            To change the 
 
values in the selected parameter use buttons              and            To exit the sub menu   
 
press.        
 
MENU OPTIONS: 
         1.     Tones Settings RT (Border 2, Border 3, Border 4, Freq. RT);   2.  Tones settings ST (Frequency LT, Freq. 2, Freq. 3, Freq. 4, Freq. 5); 
 
 
  
						

							ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 23 
Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.  
 
 
 
 
 
 
3. Other Settings (Duration ST, Economy Mode, GS Filter, Rate MM,EMI Filter MM). 
TONE SETTINGS RT 
               In this menu you can adjust the audio VDI boundaries for the RT tones to suit your 
particular needs. As well as adjusting the frequency of the audible threshold. You can narrow 
or spread out the audio range to fit any particular detecting needs.                
TONE SETTINGS ST 
               In this menu you can change the frequency of the ST border tones to fit your 
personal preferences. The higher the number, the higher the pitch. The lowest tone 
corresponds to iron, while the highest to the highly conductive metals. Please consider when 
changing the lower ST tone, that the tone of the channel RT has its own distinct value 
(adjustable via menu SETTING TONE ). It is recommended to try and not set the ST tones to 
the same or similar value as the RT tone as it will become indistinguishable from the latter.  
OTHER SETTINGS  
                Duration ST.   This parameter sets the level of the duration of the tone bursts in the 
Sound Modes RT-ST and RTL-ST. The far left position corresponds to the shortest tone duration.               Economy Mode [On. / Off.]   This parameter switches the current excitation level in the coil and allows you to adjust the sensitivity and power consumption to fit different search conditions (see above) 
              GS FILTER {OFF/1-20} This option allows you to choose the level of suppression of 
false alarms caused by soil with high electrical conductivity. (saline soils, sea beach, etc.).               This is especially important when using a large-size (10 and 12.5 x9, 5 ) 
search coils operating at high frequencies (14-20 kHz) due to the characteristics of 
the interaction of these coils with highly conductive soils.             It should be remembered that increasing the value of the filtering level 
increases the comfort of the search, but it can lead to missing deep or highly 
conductive targets.                The value of the filtering level should be selected experimentally for each particular detecting situation as it is desirable to keep this setting as low as possible while still maintaining a comfortable search level.               RATE MM-Not fully described. This adjusts the setting for the algorithm for targets spaced close together. This may be set experimentally. Current setting of 5 is recommended.               EMI FILTER MM- not fully described. However it appears to be self-explanatory.  
USER PROGRAMS 
The device provides the ability to edit and save 4 independent search programs. In 
each program, the user may choose to set the value of any of the available options. 
 
To switch between user programs press button            The currently selected program is 
displayed in the lower right hand corner of the display. The factory setting values for all 4  
programs are shown in Table 1: 
 
  
						

							24 ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 
Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.  
 
 
 
 
 
Table 1. 
Settings Prog. 1 Prog. 2 Prog. 3 Prog.4 
Sensitivity ST 10 10 11 12 
Sensitivity RT 7 7 8 9 
Volume 9 9 9 9 
Turbo Mode Off Off Off On 
Search mode AF2 ММ Norm AF1 
Sound Mode RT-ST RT-ST RT-ST RT-ST 
DHR Off Off Off Off 
Speed AT (Autotrak) 2 Off Off Off 
Gain 7 7 7 7 
Accumulation 1 3 3 3 
Scale of the screen 1:4 1:7 1:7 1:2 
Number of tones 5 5 5 5 
Border LT -14 -24 -24 -24 
Vol. WS 6 6 6 8 
Volume LT 9 6 9 9 
Shift Freq. Center Center Center Center  
Settings:  Backlight,  Contrast  and  Cont.  CT  directly  with  the  search  capabilities  of 
the  device  are  not  affected,  and  can  be chosen  based  on  the  preferences  of  the  particular 
user. However, one should pay attention to two points: 
-Unless absolutely necessary, do not place a high value for the Backlight setting,  
Doing so may reduce the operation time with one set of batteries. 
- It is also not recommended to set too high a level for the parameter Duration ST 
when working in trashy areas, for a clearer separation of closely spaced targets. 
  Factory  default  values for  all  parameters  are  stored  in  memory  and  the  user  can 
always go back to them. To perform this you must first turn on the device while at the  
 
Same time holding down the button             and hold it until the end of the melody. 
 Program 1 is designed for easy and comfortable search of shallow objects 
 
                 Program 2 designed to search in trashy areas. Has a good response, but slightly 
inferior in sensitivity. 
                 Program 3 is the main program of research, combining the best combinations for a 
comfortable search with near maximum sensitivity.                  
                 Program 4 - for when you want to search at slightly greater depths, 
however, it is worth remembering that it reduces the comfort of searching, identifying 
deteriorating properties of the device, as well as the time from one set of batteries is 
reduced by 2-3 times. 
             Remember that the default settings are not an absolute, but offered only as a 
starting point to assist your search. Experiment and we hope that in the near future you will 
make your own comfortable and effective program. 
   
						

							ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 25 
Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.  
 
  
 
 
As we gain experience the company reserves the right, without notice, to change the value 
of the factory settings. 
             A  very  useful  practice  is  to  switch  between  user  modes  to  access  changes  in  menu 
options. A good example of this is changing “Backlight” settings. To do this there are a  pair 
of  identical  search  programs  (1  and  2,  3  and  4)  the  only  difference  is  the  value  of  the 
backlight  (one  pair  of  programs  is  on,  the  other  is  off).  Further,  if  you  need  to  change  the 
current  state  of  the  backlight,  no  need  to  go  to  the  menu  and  look  for  the  desired  setting. 
You can just toggle the search program. 
 
USING THE HODOGRAPH 
FOR IDENTIFICATION          We have previously mentioned about using the 
hodograph for identifying targets. But what is the 
hodograph and what it is for? The received signal is 
characterized not only by its amplitude and phase, 
but it is also a vector quantity. Amplitude and phase 
depend on the electro physical parameters of objects 
such as conductivity, magnetic permeability,                                                   
depth, geometry, etc. To accurately describe the                                           Fig. 14 
nature of the received signal from an object is very 
 difficult,  given  the  variety  of  influencing  factors.  However, it  is  possible  to  point  out  some 
general  patterns. Earlier,  we  mentioned  that  the  signal  is  a  vector  quantity  characterized  by 
amplitude and phase.  If  you hold any metal  object to  the coil it is evident that  the magnitude 
of  this  vector  will  vary.    The  end  of  the  vector  will  describe, on  a  coordinate  plane, some 
shapes  (lines,  loops,  etc.).    These  shapes  are  called Hodographs.    The  latter most  closely 
describes the complex interactions of the coil with metal objects. 
When analyzing the hodographs should be remember a few general rules: 
• hodographs of small and medium-sized ferromagnetic objects are in the left quadrant (i.e. 
have a negative vector angle); 
• hodographs of objects of non-ferrous metals and large ferromagnetic objects lie in the 
right quadrant (positive vector angle); 
• the larger the area of the surface of an object the higher the electrical conductivity, hence   
the greater the slope of the hodograph to the right; 
• travel times of medium and large ferrous objects, as a rule, have the shape of a loop; 
• hodographs of non-ferrous metal objects are mainly straight; 
• a properly ground balanced unit will have a vector along the horizontal axis. Examples of the 
hodographs of some objects are shown in Fig. 14. Thus, analyzing the shape and position of 
the hodograph, along the coordinate plane, there can be a certain degree of probability as to 
the identity of the object type. It should be noted that the hodograph examples given  are 
idealized and do not take into account the effect ground mineralization. 
						

							Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации. 
26 ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 
 
 
    
REPLACING THE COIL 
Attention!  Before you replace the coil, find a clean section of ground, because after a 
coil replacement a ground balance is required. 
Or, if a clean place cannot be found, have a piece of ferrite, or use a piece of red 
brick. Secure the desired coil on the rod, wrap the wire around the rod and plug the 
connector into the control box. 
Hold the device at a distance of half a meter between the coil and the ground and 
away  
 
from metal objects, turn on the unit while holding down the button             on the  
 
instrument panel. Keep the button pressed until the detector stops playing the melody, 
and the screen for a short time will display  the value of the working frequency of the  
coil. 
Attention!   The exact frequency displayed can vary depending on the coil and 
software and is automatically calculated by the device. For example a Coil with a 
frequency 7.0 kHz,  can vary  
± 20 Hz. 
After this, your device will automatically 
navigate into the ground balancing mode. 
(Fig. 15) Perform the auto ground balance on  
the clean area of ground you located prior to  
changing the coil. Refer to appropriate paragraph 
under section  “Ground Balance”. Alternatively if a  
section  of clean ground cannot be located perform                               Fig. 15 
the balance procedure using a piece of ferrite or 
red  brick. Refer to the instruction pertaining to this under the section “Ground Balance” 
  
Pressing           exits the balancing mode. Your device is now ready to work with the 
new coil. 
Attention! All  of  the  above procedures are necessary when  making changes to  the 
software version (flashing). 
If your unit is equipped with several periodically used coils we recommend that you in 
the  case  of  a  shutdown (e.g. seasonal),  before  starting  the  search  to  restart  the  detector, 
i.e., to avoid confusion, to adapt the electronic unit to the sensor (coil). 
 
SEARCH AND IDENTIFICATION METHODS  
     When scanning the ground move the coil smoothly over the surface of the ground 
while maintaining a constant distance of 2-3 cm This distance is optimal from the 
viewpoint of suppressing the influence of ground mineralization, and hence, for the proper 
identification of the metal objects. Avoid touching the ground with the coil. It is important 
that the distance between the coil and the ground remain constant (see Figure 16). Keep in 
mind that the quality of this operation has a direct impact on the correct identification of 
desired targets.  Also try not to make sudden movements of the coil horizontally.  Optimal 
scanning speed is 40-50 cm/s.  Each pass of the sensor should overlap the previous one. 
  
						

							ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 27 
Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.  
 
 
               Use additional scans to more accurately identify the type of object by centering 
above the target. Sweep the coil through the maximum signal area as accurately as possible 
maintaining a constant distance between the coil and ground. For the same reason scan the 
target with coil in the direction of the least amount of surface change in the ground. In this 
case, the effect of soil will be minimal. 
 
              When the search coil interacts with a metal object 
there may be a single tone burst or possibly several tone 
bursts in rapid succession. Therefore one should pay 
attention to the following. When the detector responds 
with a single short high tone and the signal level is rather 
stable it is a good probability that the targets is not very 
large and of a non ferrous nature at a depth of more than 
5cm. 
              On the other hand if the detector gives a series of 
short high tones (usually 3) then the targets is shallow and 
in the so called near zone (less than 5cm). The Signal level 
will also display a value of 50 or greater. 
              A series of two short low-pitched sounds indicates 
that in the area of the coil is an extended ferrous object 
(like a nail) located along the scanning direction. If the 
object is located along the perpendicular plane of the scan 
or the coil, the device will issue a single low-frequency 
short tone. 
 
                                                                                                                 Fig. 16 
 It is important to note that the DD sensor is characterized by a 
complex pattern when interacting with metal objects close to the coil 
or  the  near  zone (signal levels  greater  than  80). Therefore  when 
trying to determine the target ID adjust the coil height to a level that 
will give a signal strength of  30 to 60 in the Turbo mode and from 15 
to 30 in the normal search mode.              In other words, if conditions allow, try to identify objects above the near the zone. 
           Let’s us  discuss  some  of  the  challenges  with  the so-called “hot  rocks”,  (VDI  greater 
than +84). In order to better differentiate between hot rocks and relatively large flat non 
ferromagnetic objects  (Large  copper  or  silver  coins) with  a VDI  range of  +78  to +86,  the 
device  uses a  special  high  pitched  tone  which is different from  the  usual  tone indicated  on 
such non ferrous targets. If you desire the signal from hot rocks can be deleted by setting 
the  discriminator sector value  with  the  right  edge  of  the  +86.  However,  the  most  effective 
means  of  suppressing  the  audible  reaction  on  hot  rocks  is to  use  the  DHR  algorithm (Disc. 
of hot rocks). The  risk from using discrimination settings to eliminate an audio  response to 
hot rocks is this. Due to effect of the ground valuable targets, whose vector angle is close to 
that  of  hot  rocks, can being  missed.  This  risk  is  virtually  eliminated  by  using  the  algorithm 
DHR instead. 
As you know, a particular problem for induction metal detectors is the identification of flat 
 
 
 
  
						

							Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации. 
28 ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 
 
 
 
 
 ferromagnetic  objects  such  as  steel caps/stoppers,  lids,  cans,  etc.,  objects  with  a 
relatively  large  diameter of  the  eddy  currents.  This  is  largely  helped  out  by  using  our 
proprietary development – The Hodograph Display (see Fig. 19). 
In  the  interaction of such  objects with  the coil (assuming that  the  level  of 
the signal is above 20) then time curves of these objects, as a rule, are twisted or looped in 
nature and  scattered around  the  screen depending on  the  direction  of the  scan. Fig. 17 
shows the travel times of these types of signals from an iron bottle cap/stopper. 
                               
                             Normal operating mode 
 
 
 
 
 
 
 
                                                Fig.17 
 To  solve  the  problem  with  identifying  steel  caps/stoppers,  you  can  use  the  S-
algorithm, which greatly simplifies the process of  identification of small (up to  40-50 mm) 
flat iron objects. 
If you have received a questionable audio response of an object, check using the S- 
algorithm to see if it is a cap. Do not forget to monitor the signal level. This algorithm works 
effectively only when the signal level is 10 or higher.  
Analyzing  these types of  questionable  targets  is  made  much  easier  and  does  not 
require  as  much  user  experience.  The  main  job  of  identifying is  performed  by  the 
processor.  Examples  of  the  hodographs  for  the  same  cap/stopper using the  S-mode 
algorithm is shown in Fig. 18. 
                                           
                                          S-Mode Algorithm 
 
 
 
 
 
 
                                                                     Fig. 18  
 
 
 
 
 
  
						

							ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 29 
Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации.  
 
 
 
As can be seen in Figure 19, the S-type algorithm curve has hardly changed. 
                                                        Fig. 19 
 
 
 
 
 
 
          Examples of hodographs for some objects are shown in Fig. 20-25. 
 
 
 
 
 
 
                                                        Fig. 20 
 
 
 
 
 
 
                                                         Fig. 21 
 
 
 
 
 
 
                                                         Fig. 22 
 
 
 
 
 
                                                         Fig. 23 
 
 
  
						

							Селективный металлодетектор «Сигнум MFT» 7272М. Руководство по эксплуатации. 
30 ООО «фирма «АКА», +7(495)621-0481, http://aka.2000.ru  [email protected] 
 
 
 
 
 
 
 
 
 
                                                           Fig. 24 
The example in Fig. 25 shows a hodograph for two nearby objects. Dimensions of the 
Hodograph loops  will  depend  on  the  ratio  of  the  size  of  these  objects  and  the  distance 
between them. 
 
 
 
 
 
 
                                                           Fig. 25 
 
SEARCHING  FOR METAL OBJECTS WITH 
LARGE EDDY CURRENT LOOPS. 
 
These types of  objects  include,  for  example, large copper/silver  coins,  and  other 
large planar objects of non-ferrous metals with a diameter greater than 40 mm. 
Due to the particular interaction between the search coil and these types of targets certain 
difficulties arise. 
This  is  due  to  the  very  narrow  difference  between  the  vector  angle  of  these  targets  and 
those of the ground signal. 
 
 
 
 
 
 
 
 
 
 
 
                                                             Fig. 26