Ludlum Model 375/4 Radiation Area Monitor

Digital Display, Internal Energy Compensated G-M detector

For Gamma and X-ray radiation 0.1 mR/hr - 1 R/hr

Ludlum Model 375/4 Area MonitorThe Model 375/4 Digital Wall-Mount Area Monitor features an internal energy compensated GM detector with a range from 0.01 mSv/h to 100 mSv/h (1.0 mR/hr to 10 R/hr). It features a wall-mount chassis and a four-digit LED display that is readable from 9 meters (30 feet) away. Backlit indicators warn of low radiation (yellow), high radiation (red), instrument failure (red), and low battery (yellow), along with an alarm. Calibration is easily performed by moving the "cal" dipswitch to the right, and using the pushbuttons to increment or decrement the calibration constant, dead time correction, and alarm point parameters. Parameters are stored in non-volatile memory. The memory is protected if the power is disconnected. A five-decade logarithmic analog output is provided. A battery backup provides 48 hours of additional use after the primary power is removed.

Model 375/4 Specifications

Indicated Use: Area monitoring
Detector: Geiger-Mueller
Range: 0.1 mR/hr - 1 R/hr
Display: 4 digit LED display with 0.8"(2cm) character height
Display Range: 1 mR/hr - 4 R/hr
Display Units: Can be made to display in microR/hr, mR/hr, R/hr, microSv/h, mSv/h, Sv/h, cpm, cps, and others
Linearity: Reading within plus or minus 10% of true value
Response: Typically 3 seconds from 10% to 90% of final reading
Status: (green light) Indicates the instrument is functioning properly
Low Alarm: Indicated by a yellow light and slow beep (1 per second) audible tone (can be set at any point from 0.0 - 9999)
High Alarm: Indicated by a red light and fast beep (4 per second) audible tone (can be set at any point from 0.0 - 9999)
Note:Audible indicators can be configured as a single beep if desired.
Detector Fail: (red light and audible tone; greater than 68 Db at 2 feet) Indicates detector overload, no count from detector, or instrument failure
Low Bat: (yellow) Indicates less than 2 hours of battery power remaining
Connectort: Series "C" (others available )
Calibration Controls: Accessible from front of instrument (protective cover provided )
High Voltage: Adjustable from 200 - 2500 volts
Threshhold: Adjustable from 2 - 100 mV
Dead Time: Adjustable to compensate for dead time of the detector and electronics (can be read on the display)
Overload: Senses detector saturation (indicated by display reading"-OL-")
Overrange: Indicates the radiation field being measured has exceeded the counting range of the instrument (indicated by display reading "----")
Data Output: 9 pin connector providing 5 decade log output, RS-232 output, signal ground connection, FAIL and Alarm signals (current sink), and direct connection to battery and ground
Remote (optional): Model 271, or Model 272 remote units
Power: 95 - 135 VAC (178 - 240 VAC available), 50 - 60 Hz single phase (less than 100 mA), 6 volt sealed lead acid rechargeable battery (built in)
Battery Life: Typically 48 hours in non-alarm condition, 12 hours in alarm condition
Battery Charger: Battery is continuously trickle charged when instrument is connected to line power and turned on
Construction: Aluminum housing with ivory polyurethane enamel paint
Temperature Range: -4° F(-20° C) to 122° F(50° C)
May be certified for operation from -40° F(-40° C) to 150° F(65° C)
Size: 7.4" (18.7 cm)H X 9.7" (24.6 cm)W X 2.5" (6.4 cm)L
Weight: 6.5 lbs (2.3 kg)

Model 375-4 Optional Accessories

Model 375-4 Area Monitor Manual


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