Model52-1Family TechnicalManual Section1
Ludlum Measurements, Inc. Page 1-2 July 2018
(FEMA-REP-21). They are designed to be disassembled for ease of
transportation and storage, and can be assembled in five minutes or
less without tools. All parameters are stored in non-volatile memory,
which requires no battery backup. These parameters allow easy
operation with minimal setup by minimally trained personnel. The
parameters are pre-set at the factory to detect a 1.0 µCi (37.5 kBq) 137Cs
source in a 10 µR/hr (0.1 µSv/h) background field, in accordance with
the FEMA standard.
These instruments also comply with the applicable European Standards
required for CE marking of the instruments.
The electronics are microprocessor-based for ease of setup and
reliability. Status LEDs indicate count cycle status. Audible signals
(which may be turned off to avoid alarming the occupants) accompany
the LEDs for additional indication. Audio levels can also be controlled
by rotating the baffle at the front of the audio device. Detector counts,
background, and all parameters may be viewed on the Liquid Crystal
Display (LCD). All setup is accomplished by way of push buttons
located below the LCD.
These portal monitors can be operated in a walk-through basis with a
quick scan occurring while a person is positioned within the portal. In
this mode, checking is performed every 200 milliseconds while the
portal is occupied, 600 milliseconds before, and 600 milliseconds after
the portal is occupied. The portal monitor can also monitor in a stop-
and-count mode, allowing for a more sensitive scan. In stop-and-count
mode, the fixed count time may be set from 1 to 20 seconds.
These instruments have automatic background update and dynamic
alarm setting capabilities. On startup, the instrument will take a
background count and calculate alarm levels for each detector. Self-
diagnostic routines check the background count and warn if the
background becomes either too high or too low. Alarms are calculated
with a user-adjustable sigma parameter and the current background
count. During setup, the user can also specify individual alarms only,
sum alarm only, or both individual and sum alarms. The sum alarms
combine the results of the top detectors and of the bottom detectors.
All four models are able to operate from 85-250 Vac 50/60Hz. They
may also be operated from three or six “D” cell batteries using a
supplied power supply or from the supplied cigarette lighter adapter
cable. Battery lifetime is approximately 28 hours.
