Detector assembly : The instrument can be supplied with three detector probes, two detectors for Beta gamma and one for alpha, with the specifications given below.
Beta gamma detector : Side window probe with Halogen quenched GM detector, thin walled (25 / 30) mg/sq. cm. in a protective housing with a rotatable shutter for cutting off beta particles. This will be used for measuring beta as well as gamma contamination.
End window probe consisting of an End window Halogen quenched GM detector 30 mm dia, 3-4 mg/cm2 thickness mica window housed in a suitable protective cover with handle. The end-window is provided with a removable cover.
l Detection Efficiency : Greater than 2-2.5% for side shutter type probe & Greater than 15% for End window type for Sr-90 Beta particles.
l Probe Construction : Hand-held type; viewing side is provided with a removable cover.
Alpha Detector : ZnS (Ag) scintillator, approximately 20 mg /cm2 on perspex; covered by 1 mg/cm2 aluminised , pin-hole free, light-resistant mylar film, protected by a suitable thin metallic grill.
The scintillator is optically coupled to a suitable photomultiplier tube along with an appropriate low noise pre-amplifier etc.
l Detection Efficiency : Greater than 25% at centre and uniform within 5% for plutonium alphas over complete detector area.
l Probe Construction : Hand-held type; viewing side is provided with a removable cover
l Sensitive Area. : 100 sq. cm.
Electronic Unit : The electronic Unit shall comprise of Low voltage power supplies, EHT supply unit, count-rate meter based on Intel family/microcontroller, and an audio visual alarm system. The unit is provided with two UHF connectors, one for Alpha detector and other for Beta gamma detector along with the corresponding input circuit. At a time only one detector can be used.
Low Voltage power supply : The low voltage power supply unit will supply the DC power supplies required for the operation of the electronic module. It has very good line voltage and load regulation. It is fitted with Mains line filters to avoid line interferences.
EHT Supply : It provides EHT voltage for the working of the GM / scintillation detectors. Its output is continuously variable from +300V to +1500V. Output can be adjustable through front panel keypad and EHT should be displayed on the display.
Count-rate meter :
l Ranges : 0- 50, 0-500, 0-5000 and 0- 50,000 counts per minute The range selection is automatic depending upon current countrate.
l Time Constant : Varies inversely in the range of 1 sec to 10 sec.
l Display : 16x2 LCD display is provided for display of countrate and for textual message indication
The instrument also displays the reading in a calibrated LCD Bar graph display with the shape of an analog meter scale.
l Audio indication : Chirping audio is provided to indicate the contamination of the object being monitored. The audio will be one chirp per pulse.
l Overflow : > 50000 CPM
l Over load : > 99999 CPM
l Accuracy : +/ - 5% Full scale.
l Calibration Accuracy : +/- 5% Over the full range.
l Calibration Stability : Better than +/- 5% over a period of six months.
l Testing Facilities : Provision to inject a suitable pulse generator signal for routine testing of Alpha / Beta Count rate sections is provided on the rear panel.
Additionally a test pulse mode through software for checking count-rate meter is provided.
Instrument Fault indication : EHT failure: Visual alarm with flashing red LED indication & “Eht” message on LCD display
Detector failure: Visual alarm with flashing red LED & “d-Fl” message on LCD display.
Microprocessor / microcontroller failure : Visual alarm with flashing green lamp Fault indications are cleared automatically if normal status is resumed.
Audio Visual Alarm system
l Alarm setting range : 0 to full scale of the range selected
l Alarm setting accuracy & stability. : Better than + /- 10% over a period of six months .
l Alarms are indicated by Red (LED) large area window display and loud audio alarm
l Distinctive EHT/Detector failure alarm
l Large Area instrument “ON“ indication.
l Provision for display of alarm set point on demand through keypad
l Alarm set-point is adjustable continuously by the front panel keypad / hand held configurator or from Remote PC with password protection.
l Alarm annunciation scheme : The audio and visual alarm will go off automatically when the reading falls below the alarm set point.
Housing : All the electronic sub-systems are housed in a single enclosure. All the controls and display are on the front panel. The cabinet is Vapour-tight , rugged & elegant.
Remote /External Console :
l 4 - 20 mA full scale output. Output circuitry shall be able to drive 200 mtrs. of twisted pair of wires.
l Two sets of potential free contacts of Alarm relay (Change over). Contact rating 3 Amps at 250 VAC.
l 9 pin D connector for RS485 communication.
l RJ 45 connector for Ethernet port
l All these signals are terminated on a suitable connector (Allied Connectors). The corresponding unwired mating plug will be supplied with the monitor.
Computer interface : The monitor shall have a Ethernet 10/100 Mbps port for interfacing with a remote IBM PC-compatible computer. The features supported by Ethernet port are given below.
• The PC and the monitor shall operate in a host-slave configuration and the software protocol will be MODBUS/TCP.
• The firmware of the monitor shall be able to send the instrument data like Instrument ID, Instrument type, Maximum counting range, Timer range, alarm settings, alarm status, current reading etc. to the Host PC on demand.
• The firmware shall be able to receive commands from Host PC and carry out the setting of different parameters like Instrument ID, Instrument type, Maximum counting range, Timer range, alarm settings, instrument address etc.
• The PC as the host shall give commands and send queries. The monitor will carry out various functions in response to the queries.
RS-485 Specification :
Type : Isolated Multi-drop serial communication port, half duplex bi-directional communication
Address : User configurable from 0 to 255
Protocol : MODBUS RTU
Bit Rate : user 19200
Connector : 9 Pin D Type Connector
Self Diagnostics :
The monitor has built-in self diagnostics. On being powered it will perform tests to ensure that all components and sub systems are functioning properly . It will check for the Power supply, High Voltage Supply, Detector, Counting and measuring circuits, Alarm Systems and Display Systems.
The firmware will not halt monitoring / data acquisition function any time. The firmware is designed for high reliability and availability.
Test points are provided for checking the EHT voltage and jumpers are provided for connecting external input pulse signals.
Input Power : 230VAC +/-10%, 50Hz, single phase supply. Power ON/OFF indication is provided with Neon indicator. Spike suppressor and line filter are provided.
Environment : The instrument shall be able to withstand temperature upto 50o C and relative humidity upto 90% in radiation areas.
Instrument Trolley : The instrument is provided with trolley as an accessory to house all the hardware like detector probes, Electronic unit etc. The Instrument trolley is made of M.S. with castor wheels.
Environmental EMI / RFI & performance Compliance: This instrument is designed to comply to IEC 60325 for its radiation performance, environmental & EMI / RFI compliance. For EMI / RFI compliance, test specifications specified by IEC 61000 standards are applicable.