LB 111 Micro Gamma - stationary dose rate monitor

The LB 111 is a versatile instrument to measure local doses and doserates in one or two channels. It can be software-programmed for manifold applications and contains all facilities for data storage and date transmission.

The instrument is operated via a foil keypad in a menu-structured dialog. Three function keys (softkeys) are located below the display and three additional function keys to the right of the display. Parameter changes are possible only via password.



  • Compact measuring unit in a shielded metal housing with microprocessor card for connection of up to 2 detectors and with IP 65 tightness
  • All types of gamma or neutron detectors including an internal high voltage generator and a standard pulse output are suitable for connection
  • Low dose / high dose rate system
  • Radioactive gas monitor
  • Ratemeter or scaler timer mode
  • Easy to read LCD display with background illumination
  • Undirectional RS 232 interface is available for data transfer and data communication in measuring networks; another interface is provided for printer connection
  • Two electrically separated 0/4 - 20 mA analog outputs are available for connection of a recorder
  • 5 freely programmable outputs for error and alarm messages,
    2 programmable current outputs for analog display of the results (Option),
    2 alarm thresholds and 1 integral threshold per channel,
    1 fail threshold per channel (with test time interval)
  • Measuring station with alarm signals (lamps, flashlight, horn) for local warning functions
  • Password-protected parameter settings via softkey dialog
  • Locking of essential parameters through internal DIP-switches
  • Units of measurement and channel identification freely selectable
  • Typ-tested and approved by the German National Bureau of Standards (PTB Braunschweig)




The LB 111 is a versatile instrument which can be employed as a stand-alone system with local result and alarm indication.

Several LB 111 systems may be connected to one central data station inside one premise via a local network with leased line, e.g. RS 485 bus system.

Transfer of the data protocol to a central station via the local communication network with telephone modem connection is possible for large-area environmental monitoring.

The measuring electronics is installed in a compact, shielded wall housing, protection type IP 65. The signal column for local alarm indication is mounted on top of the housing. One or two probes are connected via terminals in the cable conduit of the housing.

The measurement is performed in two separate channels. The measured values of both channels can also be added, for example, to extend the range, with automatic switchover between low-dose and high-dose probe, or for summation of the gamma and neutron dose equivalent.

System Calibration

The LB 111 is type-tested and approved by ther German National Bureau of Standards (PTB Braunschweig). The calibration factor determined by PTB will be applied to all systems without further individual calibration. The parameters  essential to calibration and settings are locked by internal DIP-switches, which are accessible only when breaking a seal affixed after calibration procedure.

Measuring Methods

The count rate supplied by both digital channels can be corrected with regard to inherent background and dead-time of the connected probes before they are converted into the doserate. The digital ratemeter operates with a basic time of one second, usiing a sliding time constant for averaging, which is dependent upon the live countrate and the preselected statistical error constant.

Utility Programs

The utility programs include several very useful service funtion, for example, background determination, calibration and system test. They comprise a parameter part and the associated measuring procedure. The results obtained can automatically be entered in a user file as paramters.


General technical specifications
Measuring modesratemeter or scaler/timer
Displaytwo line 2 x 24 characters LCD display with background
Data storage

Circular buffer (FIFO) with 120 memories (version 3.1 and higher)  each for date/time, no., status, ratemeter 1, ratemeter 2, integral 1, integral 2, integral time, scaler timer 1, scaler timer 2
Temperature range-5 °C to 50 °C
Relative humidity10 % to 90 % (LB 111 type-tested from 30% to 75%)
Protection degreeIP 65
Dimensions240 x 195 x 202 mm³ (L x W x H)
Weight                    4.8 kg, metal housing


Micro-processor electronics
Data acquisition and system control take place in a 68008 computer running under 0S9 operating system
196 kB static battery buffered RAM and max. EPROM range up to 384 kB
CPU operates with a frequency of 10 MHz


Thresholds and outputs
5 freely programmable outputs for error and alarm messages
2 programmable current outputs for analog display of the results (option)
2 alarm thresholds and 1 integral threshold per channel
1 fail threshold per channel (with test time interval)


Dose rate probes H*(10)
LB 6500-4-H10, GM-probe0.1 μSv/h to 10 mSv/h 65 keV to 1.3 MeV
LB 6500-3-H10, GM-probe1 μSv/h to 1 Sv/h 50 keV to 1.3 MeV
LB 6360-H10, Proportional counter50 nSv/h to 20 mSv/h 35 keV to 1.3 MeV
LB 6701L-H10, Ionisation chamber10 μSv/h to 10 Sv/h 50 keV to 1.3 MeV
LB 6701M-H10, Ionisation chamber100 μSv/h to 100 Sv/h 50 keV to 1.3 MeV
LB 6701H-H10, Ionisation chamber1 mSv/h to 1000 Sv/h 50 keV to 1.3 MeV
LB 6411 for neutrons30 nSv/h to 100 mSv/h 10 meV to 20 MeV



The stationary dose rate measuring device LB 112 is designed for monitoring radiation fields in the environment, especially at workplaces, in nuclear facilities, hot cells, nuclide laboratories and similar facilities.

You need a variety of different detectors to cover the complete dose rate range, for example, low dose counters, high dose counters, Geiger-Müller or proportional counters, ionization chambers and neutron dose rate detectors. The dose rate monitoring systems for environmental monitoring networks in the vicinity of nuclear facilities also require stationary dose rate measuring devices.

Further applications are, for example, process monitoring in PET centers, and online monitoring of radioactive gases.


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LB 111 en PDF 2.42 MB