Study of the tactical and technical characteristics of the programmable metal detector PMD 1.

Study of the tactical and technical characteristics of the programmable metal detector PMD 1.

Material received in April 1999.

STUDY OF TACTICAL AND TECHNICAL CHARACTERISTICS
programmable metal detector «PMD 1»

The purpose of this study was to determine the probabilistic characteristics of the programmable metal detector «PMD 1» when carrying simulators through a controlled passage: a pistol (IP) and personal items (PLP).

The programmable metal detector «PMD 1» is manufactured by the Italian company C.E.I.A.

Technical specifications:
(according to the operating documentation)

The design version of the product with column-shaped stands and a separate electronic unit was tested. Software version 4.2.

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 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 product operating modes were selected:

• processing programs: a70, a79, a91, a115;
• sensitivity modes: 0, 5, 20, 25;
• frequency modes: 1, 15.

With the signal processing program a79 and frequency mode 1, measurements were taken in sensitivity modes 0; 5; 20.

In sensitivity mode 20 and frequency mode 1, measurements were taken with three more signal processing programs: a70; a91; a115.

In sensitivity mode 20, processing program a115, measurements were taken for frequency mode 15.

In addition, measurements were taken in the automatic installation mode of the metal detector when it was turned on:

• sensitivity mode 25;
• processing program a79;
• frequency mode 1.

4. The obtained research results are presented in tables 1-4.

Table 1

Table 2

Table 3

Table 4

The measurement results for the a115 processing program, sensitivity of 20 conventional units and frequency mode of 15 are similar to those presented in Table 4.

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

4.1 Of the nine points considered in the area controlled by the metal detector, the worst results for detecting the IP were obtained for point 5. Therefore, the detection characteristics of the product are further assessed based on the results obtained at this point.

The worst results for false alarms when carrying the PLP were found at points 7 and 9. Therefore, the selective characteristics of the product are assessed based on these points.

According to the Poisson theorem, as the number of experiments increases, 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 probabilities of detecting the IP (Pbn.) and the LLP (Pl.t.).

For point 5, with a sensitivity of 25 conventional units, where Pl.t.=0.6, the probability that, with 30 experiments, the error in replacing p* with Pl.t. does not exceed 20% is 0.82. For point 9, with a sensitivity of 25 conventional units, where Pl.t.=0.63, the probability that, with 30 experiments, the error in replacing p* with Pl.t. does not exceed 20% is 0.85.

Fig. 3 shows the dependence graphs of the sensitivity of Robn. and Rl.t. at the worst points in the controlled area.

4.2. With an increase in sensitivity from 0 to 25 conventional units, the probability of detecting an IP increases from 0 to 0.6, while the probability of triggering from a PLP increases from 0 to 0.63.

4.3. If the least probable points of PLP carry-through (points 7, 9 in Fig. 1) are excluded from the analysis, triggering from PLP will obviously not occur.

4.4. By increasing the sensitivity, it is possible to increase the probability of detecting the IP to 0.98 — 1.0, while the selective characteristics of the product require additional assessment.

4.5. When a monitor from a personal computer is located near the receiving coil of the product, the product begins to operate at a sensitivity of 20 conventional units at distances of:

• 75 cm at a frequency of 15;
• 45 cm at a frequency of 0.