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gate monitor (1- 10000 µR hr) [type: ga 727]  
Technical Data

Gate monitor Type: GA727, manufactured & supplied by NUCLEONIX SYSTEMS is designed primarily to monitor low levels of gamma radiation. It uses state-of-art electronic devices (latest) including microcontroller with associated peripheral devices and other discrete ICs & components. Use of these devices makes it compact & highly reliable. Powerful embedded code adds-up and enhances its performance and gives extra advantage from the angle of fault diagnostics, programmable features & measurement of dose rate & data communication under networked environment. This unit is primarily designed to indicate dose rates in the measuring unit selected & produces audio / visual alarms, if the dose rate exceeds preset value. By default the unit is set to be in mR/hr & the range is (0-10000 µR/hr).

This Gate Monitor GA727 unit will be useful for monitoring Low Gamma dose rate levels in working areas of Radio Isotope Laboratories, Radiology departments, Medical & Industrial Radiological installations apart from its usefulness in Atomic Power Stations, radiochemical plants, waste immobilization plants etc.,

With power ON, initialization of hardware, peripheral devices, seven segment LED display, 16x2 LCD display / timers, counter etc, takes place. Followed by this, dose rate calculation takes place in the selected unit such as mR/hr. Additionally, hardware & fault diagnostic check will be carried out. Display updating will take place every 4 sec. Time constant (TC) for doserate will be computed depending upon the detector output count rate.

Gate monitor GA727 indicates dose rate digitally on 6x7 segment LED display as well a 16x2 LCD display. There are two visual annunciator lamp windows GREEN & RED for NORMAL & ACTIVE conditions respectively. The ACTIVE window flashes once the dose rate alarm occurs and in normal condition the NORMAL window glows.

The user interface is through a front panel keypad comprising of EHT, PROG, INC, DEC, ACK & RESET keys. PROG key shows up different menu options on successive operation. INC, DEC are used to scroll / select various PROG options. ACK and RESET are used for acknowledging and resetting the unit during Active alarm condition. The unit has user selectable options like Alarm preset level, Baud rate (for serial communication), Reset mode (auto or manual) and other system settings. Pressing EHT key displays the current EHT value in the detector probe.

For external detector arrangement, the detector probe can be connected to main Electronic unit by a multicore cable with both end connector arrangement upto a maximum of 30 meters or even more.


  • Microcontroller based design with extensive use of peripheral devices & serial bus interface has been employed.
  • Dose rate range covered is (0-10000) µR/hr by default, with option of selection of other three 'units' namely µSv/hr, & CPM.
  • Auto ranging & auto TC selection in the range of 30 sec to 0.5 sec depending upon detector count rate.
  • Large size 6x7 segment LED indication for dose rate is provided.
  • Designed using LND GM tube type GM132E or its equivalent.
  • Large size WINDOWS for NORMAL & ACTIVE alarm condition.
  • 16x2 LCD dot matrix display for visualization & setting of various options.

Radiation to be detected :
Gamma Radiation.

Range : 0 - 10000 µR/hr
0.00 - 100.00 µSv/hr
0- 50000 CPM
Range and Unit are configurable

Detector : High sensitivity energy compensated Halogen -quenched G. M. Tube GM132E or equivalent having a sensitivity of 160 cps / mR/hr

Accuracy : +/ - 10% Full scale.

EHT : 400V to 700V DC adjustable (Typical 500V)

Display : 5" TFT display is used for display of doserate information and hardware status information TFT display is used for visualization of preset alarm and other parameters.

Overload : Senses overload above 200% of fullscale and upto 1 R/h & indicates on display “OL”

Over-range : Senses if the radiation field being measured has exceeded the measurement range of the instrument and upto 200% of the instrument and displays “OFl”

Recorder output : 4-20 mA, with 600 ohm load.

Recorder output stability
(a) Non-linearity : Max = 0.025% of Span
(b) Offset current (Io=4mA):Max= 0.0005% of Span / oC
(c) Span Error (Io=20mA) : Max = 0.005% of Span / oC

Time Constant : First reading on Power ON within 5 secs.
Normal (Slow) : 30 sec to 0.5 sec automatically varying inversely with the radiation level.
Abrupt detection : Update the current reading within 2 sec and return to normal mode.

Calibration Accuracy : +/- 10% through out the range.

Instrument “ON” Indication : Large Area Green LED Lamp. This will indicate the Normal condition also.

Alarm range : 1 - 9999 µR/hr.
0.01- 99.99 µSv/hr
1-50000 CPM
The alarm level setting will be carried out through front panel keypad / RS-485 Serial port using handheld configurator / PC with password protection. Front panel keypad is provided with DIP switch de-activation.

Alarm Indication : a) Red (LED) flashing large area window display
b) Loud alternating audio tone (Dual frequency tone)

Instrument Controls :
a) Acknowledgement switch for muting audio
b) Reset switch for resetting the Alarm indication and alarm relay.
c) Power ON/OFF switch (This is inside the cabinet) with Power ON indication

Instrument Fault indication :
EHT failure : Visual alarm with flashing red LED indication & “Eht” message on display
Detector failure : Visual alarm with flashing red LED & “d-FL” message on display.
Microprocessor / microcontroller failure : Visual alarm with flashing green lamp.
Fault indications shall be cleared automatically if normal status is resumed.

Detector Housing:
a. The detector is located external to the Monitor.
b. It is housed in a suitable, air-tight SS shell with built-in pre-amplifier to drive upto 50 mtrs long cable.
c. The instrument is provided with 10 mtr cable between detector and the monitor.
d. The detector housing qualify minimum industrial protection Class IP-54.
e. The monitor have clamp on the top for fixing the detector assembly.
f. A separate mounting bracket for detector housing is provided.

Monitor Enclosure:
a. Vapour-tight , rugged & elegant.
b. The door is provided with lock and key arrangement
c. The enclosure qualify minimum industrial protection Class IP-54.
d. Decorative with visual aesthetics, prominent alarm display and good readability.

Detector housing is mounted using clamps on top of the monitor. The monitor is wall mountable type. Brackets for the monitor & detector housing are supplied along with the equipment.

Remote /External Console:
a. 4 - 20 mA linear proportional to full scale display output. Current output is able to drive load of 600 ohms. 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 Amp at 250 VAC. The relay is energized on normal condition and de-energised under alarm condition.
c. Remote alarm acknowledgement and reset signals for the field instruments (Normally open contact).
d. Indication of instrument fault condition (detector, EHT and LV supplies failure), over range & overflow conditions by up-scale 4-20 mA. (22.5 mA)
e. All these signals are terminated on a 17 pin socket (Allied Connectors). The corresponding mating plug with 5 mtr cable is supplied with the monitor.
f. RJ 45 connector for Ethernet port
g. RS-485 serial port (optional). This is in parallel with D-type connectors.

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 PC as the host shall give commands and send queries. The monitor will carry out various functions in response to the queries.
• The firmware of the monitor shall be able to send the instrument data like instrument ID, instrument type, input range, display range, alarm settings, alarm status, current reading, diagnostic status of EHT/GM tube 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, input range, display range, alarm settings, Ack, Reset, instrument address etc.

Data transfer using socket programming for transfer of last 24hr data is provided.

IP address is settable only through front panel keypad or through RS485 interface (17 pin I/O).

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 supplies, High Voltage Supply, Detector and Counting electronics.

Input Power :
230VAC +/-10%, 50Hz, single phase supply. Power ON/OFF switch is provided with a neon indicator. Spike suppressor and line filter are also provided.

Mechanical Enclosure:
Size: 357H x 410W x 140D
Weight: 8.5kg approx


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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