Model 3

Manufacturer: Ludlum
Part Number: 48-1605
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This is Ludlum's best selling, general purpose, handheld analog ratemeter known for accuracy and long-lasting dependability. The analog meter comes in a variety of measurement ranges and units to support the external radiation detector selected.

The aluminum cast instrument housing with its separate battery compartment and accompanying metal handle offer an industrial robustness and quality that promote long-lasting protection and instrument life. The front-panel controls include a rotary switch for selecting the four-decade range, instrument shut-off, battery test, an audio on/off switch, a fast/slow response switch, and a count reset button.

A one meter (39 in.) straight type detector cable with "C" style connector is included in the price of the instrument.

Key Features

  • Low price
  • Rugged
  • 4-Decade analog ratemeter
  • Supports GM & scintillation type detectors
  • Greater than 2000 hour battery life

APPLICATION: alpha, beta, and gamma surveying

DETECTION RANGE: dependent on detector


LINEARITY: reading within 10% of true value with detector connected

HIGH VOLTAGE: adjustable from 400-1500 Vdc

THRESHOLD: fixed at 40 mV ± 10 mV

METER DIAL: 0-2 mR/hr, or 0-500 kcpm, BAT TEST (See all available dials)

METER: 6.4 cm (2.5 in.) arc, 1 mA analog type


  • Rotary Selector: switches between instrument off, battery check, ranges: x0.1, x1, x10, x100
  • Response Switch: toggles between FAST (4 seconds) or SLOW (22 seconds) from 10% to 90% of final reading
  • Reset Pushbutton: to zero meter
  • Audio Switch: for audio on/off, built-in unimorph speaker, greater than 60 dB at 0.6 meters (2 ft)
  • Calibration Controls: accessible from front of instrument (protective cover provided)
CONSTRUCTION: cast and drawn aluminum with beige powder coat

CONNECTOR: series “C”

TEMPERATURE RANGE: -20 to 50 °C (-4 to 122 °F), may be certified for operation from -40 to 65 °C (-40 to 150 °F)

POWER: two each “D” cell batteries (housed in externally accessible sealed compartment)

BATTERY LIFE: typically greater than 2000 hours with alkaline batteries (battery condition can be checked on meter)

SIZE: 16.5 x 8.9 x 21.6 cm (6.5 x 3.5 x 8.5 in.) (H x W x L), including handle

WEIGHT: 1.6 kg (3.5 lb), including batteries