Model 375-31H

Area Monitor with Neutron Detector

Part Number: 48-4370

Features

• Perfect for Temporary Jobsites
• Easy Setup and Use
• Versatile Controller with Highly Visible Display
• User-Programmable Alarms
• Network and Relay Options
• 48-Hour Battery Backup
• CE Certified

The Model 375 is a versatile, compact, and easy-to-use digital electronic controller designed for monitoring radiation in areas. Its simple design accommodates many different detectors to suit a wide variety of applications, and it is equipped with a local readout and alarms. These versatile units may also be connected to an optional auxiliary indicator/annunciator to alert personnel at remote locations. The user-friendly, digital design enhances setup and operation. The Model 375 units may also be networked to a central PC-based station where data are logged and alarms posted.

This affordable and very flexible system has found its way into many applications resulting in a full complement of detectors, accessories, and options that include remote indicator alarms, printers, relay outputs, weather-proof enclosures, Ethernet networking software, industrial cameras, and more.

Sites requiring centralization of their data can link multiple 375 systems together via Ethernet and view them using a common web browser with the purchase of Ludlum’s Webpage & Service Software. This program collects all data in real time, logs data, and annunciates any alarms. The system can also send intelligent email alerts to responsible personnel and capture a picture of whatever triggered an alarm if optional Ethernet cameras are employed.

The detector is fitted with a bracket to attach to the Model 375. It consists of a cadmium-located polyethylene sphere surrounding a ³He detector. A study has demonstrated that the 9-inch cadmium-loaded sphere has a response similar to that of a 10-inch diameter rem-responding sphere.

The neutron detector is designed to detect thermal and fast neutrons (0.025 eV to approximately 12 MeV). Neutrons are detected indirectly through nuclear reactions, which result in energetically charged particles. Gamma rejection is very good, resulting in less than 10 cpm in a 10 R/hr field.

• Specifications
• Options
• Documents

• Specifications
• Options
• Documents

Specifications

Indicated Use	Area monitoring, neutron detection
Detector	2 atm 3He tube, LND 25185 or equivalent
Detector Moderator	22.9 cm (9 in.) diameter cadmium-loaded polyethylene sphere
Measurement Range	0 to 100 mSv/h (0 to 10 rem/hr)
Energy Response	Thermal to 12 MeV; approximately follows the radiation protection guide curve for neutron dose
Sensitivity (241AmBe)	10,000 cpm per mSv/h (100 cpm per mrem/hr)
Gamma Rejection (137Cs)	10 cpm or less, up to 0.1 Sv/h (10 R/hr)
Operating Voltage	1200 V (typical)
Input Sensitivity	-2 mV
Display	4-digit LED display with 2 cm (0.8 in.) character height
Display Range	000.0 to 9999 (Series One: 00.00 to 9999)
Display Units	µSv/h, mSv/h, mrem/hr, or rem/hr
Linearity	Readings within 10% of true value
Response	Typically 3 seconds from 10% to 90% of final reading
Indicators	STATUS: green light, instrument functioning properly LOW ALARM: yellow light and slow beep (1 per second), can be set at any point from 0.0 - 9999 HIGH ALARM: red light and fast beep (4 per second), can be set at any point from 0.0 - 9999 DET FAIL: red light and audible tone; for conditions of detector overload, no count from detector, or instrument failure LOW BAT: yellow light, indicates less than 2 hours of battery power remaining OVERLOAD: display reading of "-OL-" and audible FAIL alarm indicate detector saturation OVER-RANGE: display reading of "----" and activated low and high alarms indicate that the radiation field being measured has exceeded the counting range of the instrument (or when dead time correction accounts for more than 75% of the displayed reading)
Remote (optional)	Allows for connection of Ludlum Model 271 or 272 remote units
Relays	Fail-safe form C relays included
Connector	Series "C" (others available)
Ethernet (optional)	10 Base-T connection for use with Ludlum software
Calibration Controls	Accessible from the front of instrument (protective cover provided)
High Voltage	User-adjustable from 450 to 2500 volts
Dead Time	User-adjustable to compensate for dead time of the detector and electronics (can be read on the display)
Audio	Intensity can vary from approximately 68 dB to 100 dB through operation of the external rotary baffle and internal voltage connection. Frequency is approximately 3 kHz.
RS-232 Output	A 2-second dump for computer data logging
Power	9 Vdc wall-mount adapter handles any mains voltage in the world, supplied with four sets of prongs for almost any style wall receptacle
Battery Life	Typically 48 hours in non-alarm condition; 12 hours in alarm condition
Battery Charger	Battery is continuously trickle charge when the instrument is connected to line power and turned on
Construction	Area Monitor: aluminum housing with ivory powder-coat finish Brackets: drawn-and-cast aluminum with ivory powder-coat finish Sphere: polyethylene
Temperature Range	-15 to 50 °C (5 to 122 °F), may be certified for operation from -40 to 65 °C (-40 to 150 °F)
Size (H x W x L)	45.7 x 25.4 x 27.9 cm (18 x 10 x 11 in.)
Weight	9.5 kg (21 lb)

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Options

Option	Description	Part Number
Model 375 Series Options	Various options are available for the Model 375 Series including: Enclosures Remote displays Alarm annunciators Signal outputs Software & networking options	Various

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Documents

• Data Sheet
• Product Manual
• Ethernet Manual Addendum (for instruments with ESP32 Ethernet board)
• CE Certificate
• Ludlum Neutron Meters Comparison Table

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