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HIGH area Gamma monitor [type: HG 726]  
Technical Data
High Area Gamma Monitor type HG726, manufactured by NUCLEONIX SYSTEMS employs state-of-art microcontroller based design and is primarily meant to serve as a Gamma Zone Monitor to indicate dose rates and give alarm, visual and aural, once the dose rates exceed the preset level fixed by the user. Also relays will be activated on alarm. This unit will be useful for monitoring Gamma dose rate levels in working areas of radioisotope laboratories, radiology departments, medical & industrial radiological installations apart from its usefulness in Atomic Power Stations and other active labs. This unit indicates the dose rate digitally on a 4 x 7 segment LED display. Each of the annunciator windows for NORMAL and ACTIVE conditions has LED array. Once alarm triggers ACTIVE window starts blinking. Unit can be programmed / configured using front panel keypad which can be deactivated after completion of programming. Configuring the unit namely setting preset level, setting reset mode - AUTO/MANUAL etc are achieved by this keypad. Unit also performs self-diagnostics for HV failure, pulse processing electronics failure & detectors failure on power up. Alarm acknowledge and reset pins are provided on the circular I/O connector for remote acknowledge & reset. RS485 port is also available optionally.

  • Performance specifications confirm to ANSI N42.17A
  • EMI/EMC compliance as per IEC 61000.
  • Structural design seismic qualified confirming to IEEE-344 STD.
  • Instrument enclosure and detector assembly are IP-54 compliant.
  • Radiation tolerant upto 104 R.
  • Microcontroller based design has been employed
  • Dose rate range covered (0.1 - 999.9) R/hr
  • Auto ranging & auto TC selection in the range of 4 sec to 0.5 sec depending upon dose rate
  • Large size 4x7 segment LED indication for dose rate is provided
  • Designed using Energy compensated tube.
  • Large size WINDOWS for NORMAL & ACTIVE alarm condition
  • 4 to 20 mA current loop / 0-5V analog. Output is available for remote indication on a I/O connector (optional)
  • 16x2 LCD dotmatrix display for visualization of other parameters.

1. Radiation detected :
X – ray & Gamma Radiation

2. Range : 0.1 R/hr to 999.9 R/hr

3. Detector : Halogen quenched energy compensated GM tube.

4. Accuracy : +/-15% (from 1% to 100% of the full scale)

5. Display : Auto – ranging direct reading, 4 digit 7 segment LED display & 16x2 LCD display. 4 x 7 segment display is interfaced using multiplexed display driver IC. 4x7 segment is used for display of dose-rate information & 16x2 LCD for visualization of preset alarm & other parameters.

6. Time Constant : Time constant will be continuously variable from 4 sec to 0.5 sec decreasing linearly with counts.

7. Calibration Stability :
Better than +/-10% over a period of six months.

8. Alarm range :
0.1 R/hr to 999.9 R/hr
Alarm setting accuracy & stability
Better than +/-10% over a period of six months.

9. Alarm System :
a. Alarm will be indicated by Red (LED) flashing large area window display and Loud audio alarm (90db).
b. Distinctive HV / Detector failure alarm


c. Provision for display of alarm set point.
d. Alarm set-point will be adjustable continuously
e. The instrument will have alarm acknowledgement and Reset switches
f. Provision for remote alarm acknowledge and reset
*g. Alarm annunciation scheme: as tabulated below (default)

* Note: Any minor variations (from default condition) in Alarm sequence scheme (if user requires) can be implemented.

10. Monitor Enclosure :
Vapour-tight, rugged & elegant, and door is provided with locking arrangement.
The instrument can be offered with compliance to IP standards.

11. Mounting :
Unit is wall mountable.

12. Remote/External console :
a. 4-20 mA & 0-5 Volts full-scale output. Output circuitry shall be able to drive 200 mtrs. of twisted pair of wires.
b. Two sets of potential free contacts of Alarm relay (Change over). Contact rating 3 Amps at 250 VAC.

c. Remote alarm acknowledgement and reset signals for the field instruments.
d. Front panel Acknowledge & Reset (deactivation by jumper selection)
13. Data Storage :
A serial EEPROM to store the preset alarm levels and other settings apart from the dose rate alarm information has also been provided.

14. Self-Diagnostics :
The monitor will have 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 High voltage supply, Detector and pulse processing electronics .

15. Power :
230 VAC +/-10%, 50 Hz, single-phase supply.

16. Environment :
The instrument will be able to withstand temperature upto 60 deg C and relative humidity upto 90% in radiation areas.

17. Front panel keypad : Keypad provided on Front Panel facilitates user to configure & program the Area Monitor (deactivated by jumper selection).


1. External Detector Probe :
The G.M. Detector probe will be located external to the Monitor. It shall be housed in a suitable, airtight S.S./ Aluminium shell. Connecting cable between the detector and the monitor will be 10 mtrs (typical). Extra length optional.

2. Detector :
Halogen quenched cylindrical GM tube LND7165 (Energy Compensated) in place of non-energy compensated LND716.

3. Computer Interface :
The monitor will have a RS-485 Serial Communication port for interfacing with a PC. The PC and the monitor will operate in a host-slave configuration in a multi drop network through this interface.

The PC, as the host will give commands and send queries. The monitor will carry out the various functions as per the required information in response to the queries.

The firmware of the monitor will be able to send the instrument data like instrument ID, Instrument type, input range, display range, alarm settings, alarm data, current reading etc to the Host PC and carry out the setting of different parameters like instrument ID, Instrument type, input range, display range, alarm settings etc. The user will provide detailed list of the command and response for the Host-slave communication.

The detailed specifications for the interface will be as follows :

Type : RS-485 Multi drop Serial Communication Port, Half-duplex bi – directional communication
Protocol : MODBUS RTU
Bit Rate : Baud rate will be 9,600 by default. VB software & configurator will be able to communicate at these baud rates.

Device address is to be entered using PC. Address range is 0-99. Each of the units should have distinct address. This address is stored in EEPROM and whenever an address command is received from central console, if address matches to this monitor, it will respond to the queries.
Connector : 9 pin D-type connector

4. EMI / EMC Compliance :
Unit can be offered with EMI/EMC complaince on request at extra cost.

5. Networking Solutions :
Gamma Link Software GL910 (for RS485 Networking)

6. Hooter for aural Alarms :
A 230V AC powered hooter generating 100 db o/p with different user selectable tones can be offered in lieu of speaker.

7. Lock & Key :
This is not provided by default. It can be provided at extra cost only when the user orders specifically

Plot No.162 A & B, Phase-II, IDA, Cherlapally, Hyderabad-500051 India Phone:+91-40-27263701,27262146,040-68888777, Fax : 040 - 27262146
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