Study of tactical and technical characteristics of the Metor-200 walk-through multi-zone metal detector.

Study of the tactical and technical characteristics of the Metor-200 walk-through multi-zone metal detector.

Material received in April 1999.

STUDY OF THE TACTICAL AND TECHNICAL CHARACTERISTICS
of the Metor-200 walk-through multi-zone metal detector

The purpose of this study was to determine the probabilistic characteristics of the Metor-200 walk-through multi-zone metal detector when carrying simulators through a controlled passage: a pistol (IP) and personal use items (PLP).

The Metor-200 metal detector is manufactured by the Finnish company Metorex International Oy.

Technical specifications:
(according to the operating documentation)

The tests were carried out according to the following methodology.

1. In the controlled passage of the product, nine points were identified, the location of which is shown in Fig. 1.

2. The sought-after search objects, located in space sequentially in three mutually perpendicular positions, as shown in Fig. 2, were carried through each of the identified points.

The IP corresponded in characteristics to a PSM-type pistol, and the PLP corresponded to a set of personal metal items with a total weight of 180 g.

The number of passes through each point in each position was ten, and the total number of passes of each object through the metal detector was 270. For each point, the response frequency p* of the product was calculated for 30 passes of the IP and PLP in all three positions.

3. The following operating modes of the product were selected:

• processing programs: 01, 02, 04, 05;
• sensitivity modes: 10, 25, 30, 40;
• frequency mode 5.

With signal processing program 02, measurements were taken in sensitivity modes 10; 25; 30, 40.

In sensitivity mode 30 and frequency mode 5, measurements were taken in three more signal processing programs: 01, 04, 05.

4. The obtained research results are presented in Tables 1 and 2.

Table 1

Table 2

5. From the analysis of the obtained characteristics of the metal detector it follows:

5.1 Of the nine points considered in the zone controlled by the metal detector, the worst results for detecting the IP were obtained for points 5 and 8. Therefore, further, the detection characteristics of the product are assessed based on the results obtained at these points.

The worst results for false alarms when carrying the PLP were found at point 7. Therefore, the selective characteristics of the product are estimated at this point.

According to the Poisson theorem, with an increase in the number of experiments, the frequency p*

converges in probability to the arithmetic mean of the probabilities in each experiment. Therefore, we will consider p* to be an approximate value of the detection probabilities of the IP (Pbn.) and PLP (Rl.t.).

With the processing program 02 for point 5 with a sensitivity of 30 conventional units, where RBn. = 0.83, the probability that with 30 experiments the error in replacing p* with RBn. does not exceed 20% is 0.98. For point 7 with a sensitivity of 30 conventional units, where RBn. = 0.6, the probability that with 30 experiments the error in replacing p* with RBn. does not exceed 20% is 0.82.

Figure 3 shows the graphs of the dependence of RBn. and RBn. on sensitivity. at the worst points in the controlled area with processing program 02.

5.2 With processing program 02, increasing the sensitivity from 10 to 40 conventional units ensures an increase in the probability of detecting the IP from 0.47 to 1.0, while the probability of triggering from the PLP increases from 0 to 1.0.

5.3 With a sensitivity of 30 conventional units, changing the processing program led to different combinations of the probability of detecting the IP and the probability of triggering from the PLP (see Figure 4). Program 01 ensured reliable selection of the PLP with 100% probability of detecting the IP.

5.4 When a television set (line scan frequency of 16 kHz) and a personal computer monitor (line scan frequency of 30 kHz) were located near the receiving coil of the product, no false alarms occurred (processing programs 01, 02).

When a source of powerful low-frequency interference (50 Hz) was located near the receiving coil, alarms occurred:

• at a distance of 80 cm from the receiving coil with a sensitivity of 10 conventional units and program 02;
• at a distance of 85 cm from the receiving coil with a sensitivity of 30 conventional units. and program 02;
• at a distance of 85 cm from the receiving coil with a sensitivity of 30 conventional units and program 01;

6. The product was tested under conditions of exposure to fairly strong interference from surrounding electrical installations not related to the tests. Under these conditions, with program 05, false alarms of the product periodically occurred.