LB 9140 Transportable α-β Moving Filter Monitor

The particulates monitor LB 9140 is used to measure airborne Alpha-/Beta particulates in the presence of naturally occurring (Radon) activity and fluctuating gamma backgrounds. 


  • Si-CAM detector unit 600 mm² for simultaneous separated Alpha-/Beta measurement on a flat dust collection area of 25 x 25 mm²
  • Prompt artificial Alpha-/Beta activity measurement with Radon progeny compensation through ABPD & AED compensation method
  • Optional gamma compensation detector mountable in the same geometry as the prompt Alpha-/Beta detector
  • Continuously moving filter with 4 selectable speeds from 5 to 15 mm/h, filter change warning before end of tape. Stepwise filter mode option
  • Small footprint, portable monitor
  • Data logger electronics LB 5340 with graphical 7” color display, intelligent peripheral modules
  • Silent, low maintenance pump unit with flow low check and 3 m³/h flow rate
  • Optional flow meter (Mass flow meter or Vortex)

The portable monitor consists of following main building blocks:

Dust collection unit 9140µ

allows the prompt measurement of radioactive Alpha-/beta particles using Si-CAM detector

Prompt Alpha-/Beta detector

measures directly on the collection area to have a real time monitoring system


made of aluminum with protection degree IP68 envelopes the dust collection unit, filter supply and take-up spools. A plexi- glass front door allows visual inspection of the filter supply on the feed spool.

The filter advance is driven by a stepper motor unit, which allows continuous advancement of the filter tape at user selectable speeds (5/10/12.5 and 15 mm/h). Alternatively the filter can be advanced in step wise mode with user selectable time intervals. 
Pump Unit: with linear motor-driven Free Piston System (Pat.) has an internal piston inside the cylinder which is driven by an electro-magnet and spring system controlled by the alternating input current cycle. The system is quiet and vibration free, and offers the advantages of easy maintenance and a long operating life. The nominal flow is 3 m³/h with a noise level of max. 60 dB(A) at 1m. Optionally a flow meter can be offered.

Si-semiconductor Alpha-/beta detector

with 600 mm² surface and ruggedised entrance window for simultaneous, separate measurement of Alpha- and Beta activities. The detector analog signal is converted in the LB2029-40 amplifier unit into 3 norm pulse signals and an analog output suited for spectroscopy (ADC) input.

Optional second Si-semiconductor detector

with 600 mm² (or 150 mm²) surface can be used for ambient gamma radiation compensation. This guard detector is mounted on top of the prompt Alpha-/Beta detector to obtain identical geometry and the analog signal is converted in the LB2029-41 dual amplifier unit.

Analog/Digital counting electronics

LB 5340 data logger unit process the signals coming out of the amplifier. The electronics makes use of intelligent front end analog/digital modules and communicates with these via internal CAN-Bus. LB 5340 contains 3 intelligent front end modules:

  • Pseudo coincidence board ABPD
  • Multi I/O board
  • 8 fold Relay board


The monitor is equipped with self-check routines that continuously monitor the system health and alarm status:

  • Monitoring of the Pump function
  • Monitoring of the Filter tape
  • Detector Failure threshold Alpha and Beta (and Gamma if installed)
  • Pre-Alarm Threshold Alpha or Beta
  • Alarm Threshold Alpha or Beta
  • Lamp test


Structural shape                300 x 300 x 530 mm³ (W x D x H)
elapsed hour counter
flow low and filter trouble indicators (led)
fast filter advance pushbutton
reset filter timer push button
plexi door for access wetted parts
Dust collectionarea25 x 25 mm²
material medium-affected partsNi plated brass to MIL stdrd / stainless steel
Construction materialAlum side & back plate, plexi cover front
Sampling section
from inlet to filter
to DIN 25423 (06/96) stainless steel RS 316L
650 to 1100 hPa
max. -150 mbar / +25 hPa to
atm. pressure
-15 to +40 °C
-20 to +40 °C
Humidity                                Ambient
0 – 95 % RH non condensing
0 – 95 % RH non condensing















Type Glas fibre Particulates filter to DIN Whatman
N° 10, roll 12 m x 50 mm, core 25 mm dia
speed selectable 5/10/12.5/15 mm/h
fast 1000 mm/h pushbutton frontpanel
Autonomy> 3 months at 5 mm/h speed
Controls                               Filter ruptured, Filter supply low (< 3 m)







Pump Unit
Pump                     low maintenance (> 10 000 h)
silent operation (< 60 dB(A) at 1 m)
pump head max -440 mbar
typical operating -160 mbar
Flow ratetypical 3.3 m³/h at NTP
Controls                         pump head pressure switch (flow low)
typical set point 3.2 m³m/h at NTP








Alpha-Beta Detector
TypeSi-CAM 600 m² light tight
Typical efficiencies
solid sources



25% / 4 pi




25% / 4 pi

7 - 10% / 4 pi

Energy range
(preamp threshold setting)




Alpha Nat.

100 keV - 2.5 MeV

2.5 MeV - 10 MeV

7 MeV - 10 MeV

Background in system




< 0.002 cps

< 0.2 cps

Leadshield2 cm / 4 pi
Ambient gamma sensitivityBeta channel
 < 0.4 cps per µSv/h 137Cs radiation front
< 0.2 cps per µSv/h 137Cs radiation back

















Guard Detector
Type  Si-CAM 600 mm² light tight

Background in system

Beta window < 0.2 cps

Ambient gamma sensitivity

Beta channel

< 0.6 cps per µSv/h 137Cs radiation front









LB 2029-40 (one detector) /
LB 2029-41 (two detectors):
dual preamplifier / discriminator stage
built-in bias voltage generator 0-1000 V for Detector 1 and 2







Data Logger LB 5340



Enclosure LB 9140 / LB 5340


530 x 300 x 300 mm³ (H x W x D)


approx. 43 kg incl. pump and cart







approx. 1035 x 420 x 395 mm³ (H x W x D)



Alarm Unit
Type                                             LB 9140-ALARM, green system healty lamp, orange, red flashing lamps, resetable horn 90 dB(A) at 1 m
LampsLED´s 230 VAC WERMA
FunctionsReset horn, lamp test pushbutton
Connectionsmains 230 VAC connector,
remote signals DIN T 3406 6 pole male







Overal Electrical Specifications
Mains                              230VAC/50 Hz/Single phase, I nom 1 A,
Fuse : 1.6 A T, thermal safety 1.3 A






All applications where airborne Alpha and Beta particulates radioactivity has to be measured to prevent personnel exposure and to measure release rates in ducts and stacks

  • Decommissioning
  • Nuclear power
  • Source manufacturing
  • Industrial safety
  • Research


Format Size
LB 9140 en PDF 641.22 KB

News about this product

With our new mobile moving filter monitor LB 9140 airborne alpha and beta activities in room and exhaust air can be monitored with high sensitivity. Due to the silent and low maintenance pump unit an air flow rate of approx. 3.3 m³/h is possible.

Read more