Model2241-2iand-2i/2 TechnicalManual Section1
Ludlum Measurements, Inc. Page 1-1 January 2018
Introduction
he Model 2241-2i and 2241-2i/2 are portable microprocessor-based
digital Scaler/ Ratemeter instruments designed for use with
scintillation, Geiger-Mueller (GM), and proportional type detectors
to measure ionizing radiation. Data is presented on a four-digit (six
digits in the scaler mode) Liquid Crystal Display (LCD) with a moving
decimal point. A three-position switch labeled OFF/RATEMETER/SCALER
selects the desired operating mode for the instrument.
A toggle switch labeled ˝INT/EXT˝allows the user to select between internal
and external detector. The internal detector is an energy compensated GM
tube capable of measuring fields up to 4 R/hr (0.04 Sv/h) for the Model
2241-2i and up to 1 R/hr (0.01 Sv/h) for the Model 2241-2i/2.
Programmable display units (RATEMETER mode only) are represented in
either R/hr, Sv/h, cpm, or cps with multipliers of micro (µ) or milli (m) for
R/hr and Sv/h and kilo (k) for cpm or cps. The display units are auto-
ranging, enabling the readout to display a broad range of radiation levels.
The display also offers lower limit capability. For example, the display can be
set to show only values that are greater than or equal to 1 µR/hr.
This instrument incorporates independent adjustable alarms for RATEMETER
and SCALER operating modes. The RATEMETER mode has two alarm
indicators. The first-level alarm is indicated by display of the word ˝ALERT˝
on the LCD. The second-level alarm is indicated by display of the word
˝ALARM˝and by the emitting of a continuous audible tone. The SCALER
alarm condition will also display the word ˝ALARM˝and produce the same
audible tone. Both audible alarms may be silenced (acknowledged) by
depressing the RESET switch. All alarms are concurrent.
Other features include Dead Time Correction (DTC) to compensate for
detector dead time; audible click-per-event with programmable 1, 10, 100,
and 1000 divide-by; LCD backlight with programmable ON time;
programmable fixed or variable response time; and count overflow visual
