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Ludlum Model 12-4

Neutron Radiation Survey Meter

Introduction

● Neutron Dose Rate

● 9 in. Moderated Neutron Detector

● 0 to 10,000 mrem/hr Range

● Gamma Rejection up to 10 R/hr

● 4 Decade Analog Meter

● Rugged

The Ludlum Model 12-4 is an industry standard neutron radiation dose rate instrument that conforms to the RPG curve with a measuring range of 0–10,000 mrem/hr (0–100 Sv/h) from thermal to 12 MeV. The detector is a 9 in. (22.9 cm), moderated ³He tube with a gamma radiation background rejection up to 10 R/hr (100 mSv/h). The ratemeter is a four-decade analog meter, designed with an aluminum cast instrument housing incorporating a separate battery compartment, and accompanying metal handle. This design delivers industrial robustness and quality, promoting long-lasting protection and instrument life. The front-panel controls include a rotary switch for selecting the four-decade range, instrument shut-off, and battery test, an audio on/off switch, a fast/slow response switch, a count reset, and high-voltage test push-button. The Model 12-4 is a complete turn-key system and includes two "D" cell batteries.

Specifications

PART NUMBER: 48-1200

APPLICATION: neutron radiation dose rate

MEASUREMENT RANGE: 0–10,000 mrem/hr (0–100 mSv/h)
RADIATION DETECTOR: ³He proportional detector, 0.6 x 1.0 in. (1.6 x 2.5 cm) (D x L), surrounded by a 9.0 in. (22.9 cm) diameter cadmium loaded polyethylene sphere
SENSITIVITY: typically 100 cpm per mrem/hr (10,000 cpm per µSv/h) (bare AmBe neutrons)
ENERGY RESPONSE: provides an appropriate inverse RPG curve for neutrons from thermal through 7 MeV, provides response up to 12 MeV
LINEARITY: reading within 10% of actual value
GAMMA REJECTION: <10 cpm through 10 R/hr (0.1 Sv/hr) (¹³⁷Cs gamma)
OPERATING VOLTAGE: approximately 1200 Vdc
THRESHOLD: -2 mV
WORKING ENVIRONMENT: splash-proof shields for outdoor use
METER FACE: 0–10 mrem/hr, 0–2.5 kV, BAT TEST (others available)
CONNECTOR: series “C” (others available)

HIGH VOLTAGE: adjustable from 400–2500 V (can be read on meter)
DISCRIMINATOR: adjustable from 1–50 mV
CONTROLS:

Multipliers: x1, x10, x100, x1000
Response: toggle switch for FAST (4 s) or SLOW (22 s) from 10% to 90% of final reading
Reset: pushbutton to zero meter
HV Test: pushbutton to display the high voltage on the meter
Audio: built-in unimorph speaker with ON/OFF switch, greater than 60 dB at 2 ft (0.6 m)

CALIBRATION: accessible from front of instrument (protective cover provided)
POWER: 2 each "D" cell batteries (housed in sealed compartment that is externally accessible)
BATTERY LIFE: typically 600 hours with alkaline batteries (battery check on meter)
CONSTRUCTION: cast and drawn aluminum with beige powder coat finish
WORKING ENVIRONMENT: splash-proof shields for outdoor use
TEMPERATURE RANGE: -4 to 122 °F (-20 to 50 °C)
SIZE: 17.0 x 9.0 x 10.5 in. (43.2 x 22.9 x 26.7 cm) (H x W x L)
WEIGHT: 17.5 lb (7.9 kg)