Model 35 Vehicle Monitor

Vehicle-Mounted Digital Survey Meter

Model 35 Vehicle Radiation Monitor Model 35 mounted on windshield Model 35 components Model 35 display schematic


The Ludlum Model 35 is a versatile, lightweight, vehicle mounted instrument with an external detector used for alpha, beta, or gamma radiation survey. It remains unobtrusive until an alarm is reached. At that point the monitor can be quickly removed from the mount for closer inspection. Three modes of operation – RATE, MAX, and COUNT – are available for the user. Measurements can be collected in two sets of units (primary and secondary) for RATE and MAX modes in cps, cpm, Bq, dpm, R/hr, rem, or Sv/h units. The user can switch between two sets of chosen units by simply pressing the Units button.

An internal switch is used to enable or disable the front-panel setup feature to protect desired settings from inadvertent modification. Setup is also available via software available from Ludlum Measurements.

This instrument features a large, easily-readable LCD (liquid crystal display), an audio warning tone, and easy, intuitive, user-friendly design. Splash-resistant construction allows the Model 35 to be used outdoors. The instrument body is made of lightweight, durable, high-impact plastic. The Model 35 is shipped ready to use with batteries and calibration certificate.

Model 35 Various Applications

Model 35 mounted on a drone Model 35 on patrol boat Model 35 mounted on marine console


Compatible Detectors GM, Proportional, Scintillation (default BNC connector - others available)
LCD Display 3 digit LCD with large 13.4 mm (0.53 in.) digits, low-battery indicator, MAX, ALARM, MUTE
Units: (k)cps, (k)cpm, (k)Bq, (k)dpm, (µ)(m)R(/h), (µ)(m)Sv(/h), (µ)(m)rem(/h)
Display Range
0.0 cps to 99.9 kcps
0.00 cpm to 999 kcpm
0.00 Bq to 99.9 kBq
0.00 dpm to 999 kdpm
0.00 µR/h to 999 R/h
0.00 rem/hr to 999 rem/h
0.00 µSv/h to 999 Sv/h
Display range can be set to limit display to calibrated range
Backlight Built-in ambient light sensor automatically activates low-power LED backlight, unless internal dipswitch is set to continuous-on (will reduce battery life). Alarm light intensity varies based on ambient light levels.

Response Time User-selectable from 1 to 60 seconds, or auto-response rate FAST or SLOW
Alarms Count rate, Exposure/dose, 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 a user-settable time interval (default 60 seconds) of no pulses from the detector, the instrument will flash zero reading and the alarm audio will be triggered
Dead Time Correction Employs first and second order corrections for extended performance
High Voltage 400 to 1500 Vdc
Threshold 2 to 120 mV
Audio Greater than 75 dB at 0.6 (2 ft), approximately 4 kHz
Power Internal: Two alkaline or two rechargeable “AAA” batteries
External: 10 to 24 V through optional powered mount
Battery Life 100 hours, 24 hr low battery warning
Construction High-impact plastic with water-resistant rubber seals and separate battery compartment
Temperature Range -20 to 50 °C (-5 to 122 °F)
May be certified for operation from -40 to 65 °C (-40 to 150 °F)
Environmental Rating NEMA rating of 3x or IP rating of 52 with Audio Hole Seal option (hole seal option will reduce maximum volume by approximately 10 dB)
Size (H x W x L) 8.5 x 8.0 x 4.8 cm (3.4 x 3.1 x 1.9 in.)
Weight 174 g (0.38 lb)