LB 165/166 Floor Monitor

The Floor Monitor LB 165/166 is a mobile measurement device with large-area proportional counter tubes for the detection of surface contamination caused by radioactive nuclides.


The Floor Monitor is comprised of

  • a trolley with three wheels
  • a detector: Xenon detector or P10 flow-through counter tube
  • a battery or rechargeable battery operated evaluation unit for acquisition (UMo II LB 134)



The Floor Monitor is available in two versions:

The LB 165 monitor operates with the permanently filled Xenon counter tube LB 6376 and measures β- and γ-emitters.

The LB 166 monitor operates with a flow-through counter tube LB 6386 and measures α- and β-emitters. The required continuous counting gas supply (P10 gas bottle with double pressure reducer) is accommodated on the trolley. The P10 gas bottle can easily be exchanged by the user.

The evaluation unit UMo II LB 134 automatically detects the connected detector (Xenon or flow-through counter tube) and sets the program automatically, so that a detector change does not necessitate any new parameter setting.


  • mobile monitor with adjustable height
  • easy scanning of large floor areas
  • proportional counter tubes with 2000 cm² active area
  • less number of measuring points and so less time-consuming and less expensive
  • ratemeter or counter-time mode
  • alarm thresholds can be set for each measurement mode and each nuclide; exceeding of these thresholds is signaled visually and acoustically
  • up to 250 single results can be stored and printed out

The German Radiation Protection Ordinance requires that averaging is performed for measurements of surface contamination over an area of at least 100 cm². For this reasons, many measurement devices have sensitive areas between 100 cm² and 200 cm². On the other hand, contamination measurement devices with larger measurement areas are rather rare, apart from the foot detectors in Hand-Foot-Clothing Monitors.

Contamination measurements, therefore, had to be carried out using small portable instruments, even for measuring large wall or floor areas. Several thousands of measured values were needed for large-area measurements, which had to be collected and recorded, and this was rather time-consuming and expensive.

For this reason, Berthold Technologies has designed a Floor Monitor which is based on a completely new generation of extremely large-area proportional counter tubes with 2000 cm² active area. These detectors reduce the number of measuring points and thus the work load dramatically. Berthold Technologies is offering this new detector series with 2000 cm² active area for various applications, among them floor measurements. The detector is mobile and adjustable in its height, so that contaminated areas can easily be scanned.

The large area counter tubes with an active area of 2000 cm² can be set between 5 mm and 20 mm above the floor – depending on the floor conditions. We recommend using a typical height of 5 mm. The instrument specifications refer to this value.

Technical Data LB 165/166
 LB 165LB 166
Counting gasXenonArgon/Methane 90%/10
Entrance window12 µm titanium3 µm Mylar aluminized
Operating point1900 Volts1580 Volts
Flush-time counting gasN/A> 3 h
Preamplifier/Discriminator1-channel2-channel α-β-separation
Weight17 kg24.5 kg
Measurement modeβ-channelα-channelβ-channel
Background135 cps1 cps100 cps
Background at increased
γ-level of 0.3 µSv/h
300 cps1 cps250 cps
Detector typeProportional counter tube
Outside dimensions detector700 mm x 600 mm
Actvie area570 mm x 380 mm
Reference height detector5 mm above floor
Max. adjustable stroke18 mm
Minimum floor clearance5 mm above floor
Protective gridStainless steel, transmission degree 80 %,
protection against foreign bodies with radius 4 mm
Evaluation electronicsLB 134
Temperature range-15°C to +50°C
Operation                                Foil keypad with On/off button and 4 function keys as softkeys



It is employed wherever large floor areas have to be checked for radioactive contamination, e.g. in nuclear medicine, in nuclear power engineering and in many fields of research.