MODEL 2224-1
Technical Manual
Section 1
Ludlum Measurements, Inc.
Page 1-1
January 2012
Introduction
he Model 2224-1 is a portable microprocessor based radiation
survey instrument used to measure and discriminate low-level
alpha/beta radiation when used with an alpha/beta scintillation or
proportional detector.
The data is displayed by an analog ratemeter and a six-digit liquid crystal
display (LCD) counter. The ratemeter dial indicates 0-500
CPM
with four
linear range multipliers of ×1, ×10, ×100, and ×1000, producing an overall
range of 0-500 k
CPM
. The LCD is used to display the counts accumulated
during the preset count time. Four count times are available for selection
through a front-panel switch. These count times are: 0.5, 1, 2 and, 5 minutes.
The counter is reset and started by pressing the count button located in the
end of the carrying handle.
The ratemeter and LCD can display alpha only, beta only, or alpha and beta
by selecting the corresponding toggle switch selection. Audible click-per-
event tones can also be selected to discriminate beta (low pitch tone) from
alpha (high pitch tone) via the side-mounted speaker. Beta threshold,
window, and alpha threshold are adjustable to optimize alpha/beta efficiency
and count separation.
A regulated high-voltage power supply adjustable from 400 to 2000 volts
with detector overload detection is utilized to operate a wide range of
scintillation detectors. Other operating features of the instrument include
programmable audio divide-by (beta channel only), a two-position switch
(internal) for selecting the audio discrimination mode, audio headphone jack,
adjustable volume, battery test pushbutton, high-voltage display pushbutton,
and a ratemeter reset pushbutton.
The unit body is made of cast aluminum with a drawn aluminum can. The
unit is operated with two
˝
D
˝
cell flashlight batteries for operation from -10
o
C to approximately 50
o
C (14 to 122 °F). For operation to -10
o
C (14 °F),
either very fresh alkaline or rechargeable NiCd batteries may be used.
Section
1
T
