Model 26-1

Integrated Pancake Frisker

Ludlum Model 26-1 Frisker Ludlum Model 26-1 Frisker


The Model 26-1 Integrated Frisker is designed to simplify the process of detecting radioactive contamination on people and objects. Unlike other meter and detector combinations that require two-handed operation, this instrument combines the meter electronics and detector in a single, easy-to-use tool. Its design incorporates a 15.51 cm 2 (2.4 in 2 ) GM pancake detector, an easy-to-read LCD screen, an ergonomic handle, and a simple three-button interface to allow one-handed operation.

Three modes of operation are available — RATE, MAX, and COUNT — which can be selected by pressing the MODE button. RATE mode displays the current count, exposure, or activity rate. MAX mode captures the highest count, exposure, or activity rate detected; this is useful for finding a peak rate or for frisking when the display is not visible. COUNT mode allows the operator to perform a survey for a preset amount of time; depending on the chosen units, the count result can be a scaler count, a time-averaged rate, a time-averaged exposure or dose rate, or an integrated exposure or dose. Measurements can be displayed in units of cps, cpm, dpm, Bq, mR/h, or μSv/h. The user can switch between two sets of chosen units (primary and secondary) for RATE and MAX modes by pressing the UNITS button.

Other features include an auto-ranging and backlit LCD screen, “click” audio (which can be silenced), and user-settable count rate and scaler alarms. The instrument body is made of high impact plastic and water-resistant construction allows the instrument to be used outdoors. A wrist strap and lanyard are included for keeping the instrument close and secure. The instrument is powered by two alkaline AA batteries with a battery life up to 1000 hours.

Ambient Dose Equivalent Filter

The GM pancake detector has a significant over-response to gamma energies between 20 - 150 keV which produces dose measurement errors. Ludlum offers an ambient dose equivalent filter that flattens the detector’s energy response to within ± 20% referenced to 137 Cs (662 keV) over the energy range of 20 keV to 1.2 MeV. The filter simply snaps on over the detector window when dose measurements are required, and is easily removed when not needed. The dose filter is included with the

Detector Pancake GM detector, stainless steel screen (79% open)
Window Area Active: 15.51 cm2 (2.4 in2)
Open: 12.26 cm2 (1.9 in2)
239Pu: 11%
99Tc: 18%
32P: 32%
14C: 2%
90Sr/90Y: 22%
125I: 0.2%
5.5 cps per μSv/hr (3300 cpm per mR/hr) (137Cs)
99mTc : ≤ 1%
Display 3½ digit LCD with large 12.7 mm (0.5 in.) digits, low-battery indicator, MAX, ALARM
Units: (k)cps, (k)cpm, (k)dpm, (k)Bq, mR/hr, µSv/h
0.00 cps to 19.9 kcps
0 cpm to 999 kcpm
0.00 Bq to 19.9 kBq
0 dpm to 999 kdpm
0.00 to 500 mR/h
0.00 to 1999 µSv/h
Linearity ±10%
Backlight Built-in ambient light sensor automatically activates low-power LED backlight, or may be configured for 'Continuous On' (will reduce battery life)
ON / OFF / QUIET: Press to turn ON; Tap to alternate between click audio and QUIET; Hold for OFF
MODE: Alternates between RATE (count rate), MAX (captures peak rate), and COUNT (preset count time from 0 to 20 min.)
UNITS: Changes units between count rate (cpm, cps), dose/exposure (µSv/h, mR/hr), or activity (dpm, Bq)
Response Time User-selectable from 1 to 60 seconds, or Auto-Response Rate FAST or SLOW
Resolving Time Approximately 110 µs as defined by IEC 60325
Alarms Count rate and scaler alarm setpoints adjustable over the display range
Overload Protection High rate saturation protection, indicated by flashing display and audio alarm, prevents false display of lower count rates
Loss of Count Protection After 60 seconds of no pulses from detector, unit will flash a zero reading and the alarm audio will be triggered
Click Audio Greater than 60 dB at 0.6 m (2 ft)
HV Testpoint Accessible by removing battery cover, allows HV measurement and pulse injection for calibration using optional cable (PN: 8303-1044)
Temperature Range
-20 to 50 °C (-4 to 122 °F)
May be certified for operation from -40 to 65 °C (-40 to 150 °F)
Environmental Rating NEMA 3, IP 53
Power Two “AA” 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
Distance from Surface Plane to Screen 0.32 cm (0.125 inch)
Size (H x W x L) 4.6 x 6.9 x 27.2 cm (1.8 x 2.7 x 10.7 in.)
Weight 0.45 kg (1.0 lb)