Ludlum Model 26-1 Digital Survey Meter

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DETECTOR: Pancake GM (Geiger-Muller) detector, stainless screen (79% open)
WINDOW AREA: Active: 15.51 cm (2.4 in); Open 12.26 cm (1.9 in)
EFFICIENCY (
) (surface plane):
Alpha
: 11% for 239Pu;

Beta: 18% for 99Tc; 32% for 32P; 2%
for 14C; 22% for 90Sr/90Y;
0.2% for 125I

Gamma: 3300 cpm/mR/hr or 5.5 cps/μSv/h (137Cs); ≤1% for 99mTc

RESOLVING TIME: Approximately 110 microseconds as defined by IEC 60325

ALARMS: Count rate and scaler alarm setpoints adjustable over the display range.

OVERLOAD: High count rate saturation protection prevents false display of lower count rates

ZERO PROTECTION: After 60 seconds of no pulses from detector, unit will flash a zero reading and the alarm audio will be triggered

LCD DISPLAY: 3 digit LCD with large 12.7 mm (0.5 in.) digits, (k)cps, (k)cpm, (k)dpm, (k)Bq, mR/hr, Sv/h, Bq, and dpm; low-battery indicator, MAX, ALARM
RANGE: 0.1 cps to 19.9 kcps, or 1 cpm to 999 kcpm, 0.0 to 500 mR/hr, 0.01 to 1999 Sv/h; 0.1 to 19.9 kBq; 1 to 999 kcpm
BACKLIGHT: built-in ambient light sensor automatically activates low-power LED backlight, or may be configured for ‘Continuous On’ operations (will reduce battery life)
CONTROLS: three pushbuttons
ON/OFF/QUIET: press to turn ON, tap to alternate
between ‘click’ audio and QUIET, hold for OFF
MODE: alternates between NORMAL (count rate)
and MAX (captures peak rate), and COUNT
(user-selectable preset count time from 0
to 20 minutes)
UNITS: changes units from count rate (cpm, cps) to dose/exposure (Sv/h, mR/hr) to activity (dpm/Bq)
RESPONSE TIME: user-selectable from 1 to 60 seconds, or Auto-Response Rate FAST or SLOW
CLICK AUDIO: greater than 60 dB at 0.6 m (2 ft)
POWER: two “AA” alkaline batteries
BATTERY LIFE: approximately 1000 hours of operations (as low as 500 hours with backlight configured for ‘Continuous On’), 16-hour low battery warning-
CONSTRUCTION: high-impact plastic with water-resistant rubber seals and separate battery compartment
ENVIRONMENTAL RATING: NEMA 3/IP 53

TEMPERATURE RANGE: -20 to 50 C (-4 to 122 F), may be certified for operation from -40 to 65 C (-40 to 150 F)
DISTANCE FROM SURFACE PLANE TO SCREEN: 0.32 cm (0.125 inch)
SIZE: 4.6 x 6.9 x 27.2 cm (1.8 x 2.7 x 10.7 in.) (H x W x L)
WEIGHT: 0.45 kg (1.0 lb)