ECOTEST BDBG-09, Руководство по эксплуатации, Страница: 8 / 46

Operating manual ВІСТ.418266.006-03 НЕ
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The case of the detecting unit (according to Figure 2) consists of two parts: a base (1) and a
barrel (2). A printed-circuit board (3), with electric circuit elements placed on it, is attached with its
bottom part to the base (1). An insulator (4), located in the top part of the printed-circuit board (3),
serves to fix it inside the barrel (2). An external electric coupler (5) is adjusted in the bottom part of
the base (1) with the help of four screws. The detecting unit is sealed with circular rubber pads (6)
that protect it from the influence of external climatic factors.
Figure 2
1.4.2 Operation principle of the detecting unit
The detecting unit consists of a microcontroller, a high sensitivity detector, a low
sensitivity detector, a supply voltage former, and an RS-485 interface node.
Operation of the detecting unit is based on the method of gamma radiation transformation
into voltage pulse train on the detectors’ outlet. The high sensitivity (СБМ-20) and low sensitivity
(СИ 3БГ) Geiger-Muller counters are used in the detecting unit as the detectors.
The microcontroller processes the pulse flow from the detectors, and forms gamma
radiation DER value, which corresponds to the flow, with the account of personal background of
the detectors. The microcontroller also calculates a maximum value of DER measurement
statistical error for each gamma radiation DER value. At the same time the microcontroller runs
the power supply of the detectors and continuously controls their operability. If requested by the
data display system, the microcontroller sends a protocol frame via RS-485 interface nod. The
protocol frame contains information about current gamma radiation DER, maximum statistical
error of its measurement, and results of the operability control of the detectors.
The nonvolatile memory is a part of the microcontroller and serves for storage of
calibration factors. These factors allow considering and compensating the detector sensitivity
dispersion, and linearizing the counting feature of the detectors within the measurement range. If
requested by the data display system, the microcontroller sends a frame with current calibration
factors via RS-485 interface nod, or receives a frame with new calibration factors for storage in
the nonvolatile memory. The communications protocol is presented in the Appendix C.
The supply voltage former transforms voltage of the external power source into
3.3 V voltage for power supply of the secondary part of the detecting unit circuit, and generates
anode voltage of the high sensitivity and low sensitivity detectors.