The monitor is composed of two detector panels which are mounted opposite each other. The distance between the two detectors can vary between 3 m and 6 m. The gamma detector and the electronic measuring equipment are located in a weatherproof metal housing, data are transferred between the detectors and the control unit by cable. The optical and acoustic alarm devices are directly mounted on the housing and on the control unit. Sensors determine whether a vehicle is in the measuring location and start the measurement process automatically.
The gamma detector consists of an organic plastic scintillator with a volume of 12 liters. Each detector column contains two of these scintillators. With the exception of the measuring window, the scintillators are shielded with low-activity lead to minimize the influence of background radiation. This lead coating is further used as a collimator for the measuring window.
The control electronics has a modular design and is located within the detector housing. It includes of a microprocessor control unit with data transfer, a power supply, a high voltage for supplying the gamma detectors, and pulse processing.
Data are acquired and evaluated in the control unit. The evaluated data are shown on a display, and any alarm is additionally indicated acoustically and optically. The control unit saves the data of an alarm and forward them to a personal computer. Data are transferred between the detectors and the control unit using an RS-485 interface. Up to 16 detector columns can be connected to one control unit. The housing is dirt- and waterproof. Operation of advanced functions is performed via a keypad. Measurement of vehicles and background radiation is fully automatic. Other than alarm confirmation, no operation is required.