International Medcom Radalert 50 Manual de usuario
Radalert50
™
Nuclear Radiation Monitor
Operating Manual
Radalert 50
Nuclear Radiation Monitor
Operating Manual
Copyright 1997 by International Medcom, Inc. All rights reserved.
Contents
1 Introduction 1
How the Radalert 50 Detects Radiation 1
2 Features 2
The Display 3
The Switches 4
The Detector 5
ThePorts 5
3 Operation
Starting the Radalert 50 6
Operating Modes 6
Operating Ranges 7
Taking a Total Count 7
Using the Alert 8
Interfacing to an External Device 9
4 Common Procedures 10
Establishing the Background Count 10
Environmental Area Monitoring 10
Checking an Object 11
5 Maintenance 12
Precautions Troubleshooting 12
6 Basics of Radiation and Its Measurement 15
Ionizing Radiation 15
Measuring Radiation 17
Radiation Measurement Units 18
Determining What Is a High Reading 18
Appendix A Technical Specifications 21
Warranty 22
1Introduction
The Radalert™ 50 is a health and safety instrument that measures alpha, beta, and
gamma radiation. With the Radalert 50, you can:
• Monitor possible radiation exposure while working near radionuclides
• Ensure compliance with regulatory standards
• Check for leakage from X-ray machines and other sources
• Set the alert level and use the Radalert 50 in Alert mode; if the radiation goes
above the level you set, the alert beeper sounds to let you know
• Screen for environmental contamination or environmental sources of radioactivity
• Connect the Radalert 50 to a computer or data logger to record and tabulate your
data
This manual gives complete instructions for using the Radalert 50 and procedures
for common applications.
How the Radalert 50 Detects Radiation
The Radalert 50 uses a Geiger-Mueller tube to detect radiation. The Geiger tube
generates a pulse of electrical current each time radiation passes through the tube
and causes ionization. Each pulse is electronically detected and registers as a
count. The Radalert 50 displays the counts in the mode you choose: counts per
minute (CPM), milliroentgens per hour (mR/hr), or total counts.
1
2Features
The Radalert 50 measures alpha, beta, gamma, and x-ray radiation. This chapter
briefly describes the Radalert 50's functions. For more information on how to use the
Radalert 50, see' Chapter 3, "Operation."
The Radalert 50 counts ionizing events and displays the results on the liquid crystal
display (LCD) (4). You control which unit of measurement is shown by using the
mode switch.
2
Whenever the Radalert 50 is operating, the red count light (1) flashes each time a
count (an ionizing event) is detected.
The Display
Several indicators on the LCD show information about the mode setting, the current
function, and the battery condition.
• The numeric display (A) shows the current radiation level in the unit specified
by the mode switch setting.
• A small battery (B) appears to the left of the numeric display to indicate low
battery voltage.
• A radiation warning icon (C) appears when the Radalert 50 is in Alert-mode.
• An hourglass (D)appears to the left of the numeric display during the first
minute the Radalert 50 is operating, to show that the reading is not yet complete.
• TOTAL (E) appears when the Radalert 50 is in Total mode.
• X1000 (F) appears when the radiation level is displayed in X 1 000 mode.
• SET (G) appears when you are setting the alert level.
• The current unit of measurement (H)-CPM or mR/hr-is displayed to the right of
the numeric display. The European version of the Radalert 50 uses µSv/hr rather
than mR/hr.
3
The Switches
The Radalert 50 has two switches on the front, and three buttons on the end panel.
Each switch has three settings, which are described below.
On/Off/Audio Switch (6)
Audio. The Radalert 50 is on, and it makes a clicking sound for each
radiation event detected.
On. The Radalert 50 is operating, but audio is off.
Off. The Radalert 50 is not operating.
Mode Switch (5)
mR/hr. The numeric display shows the current radiation level in
milliroentgens per hour from .001 to 50.
CPM. The display shows the current radiation level in counts per minute from
0 to 50,000. When X1000 is shown, multiply the numeric reading by 1000 to
get the complete reading.
Total. The display shows the accumulated total of counts starting when the
switch is turned to this position, from 0 to 60,000. When X1000 is shown,
multiply the numeric reading by 1000 to get the complete reading.
The Alert Buttons (8)
The Set button turns Alert mode on and off and allows you to adjust the alert levels.
The + and - buttons adjust alert levels, using the numeric display. For more
information, see "Using the Alert" in Chapter 3.
4
The Detector
The Radalert 50 uses a Geiger tube to detect radiation. Alpha radiation does not
penetrate most solid materials, so this Geiger tube has a thin disk of mica, which
alpha radiation can penetrate, on its end. The screened opening at the top of the
Radalert 50 is called the window. It allows alpha and low-energy beta and gamma
radiation to penetrate the mica end of the tube.
CAUTION: The mica end surface of the Geiger tube is fragile. Be careful not to let
anything penetrate the screen.
The Ports
There are two ports on the left side of the Radalert 50.
The audio output (2) on the side of the Radalert 50 allows you to interface the
Radalert 50 to an external speaker, amplifier, or tape recorder using a 2.5 mm plug.
The data output port (3) below the audio output port allows you to interface the
Radalert 50 to a computer, data logger, or other device using a 3.5 mm stereo plug.
For more information, see "Interfacing to an External Device" in Chapter 3.
5
3 Operation
The guidelines in this chapter describe how to use the Radalert 50.
Starting the Radalert 50
Be sure that a standard 9-volt alkaline battery is installed in the battery compartment
in the lower rear of the Radalert 50. Note: When installing the battery, place the
battery wires along the side of the battery and not under it.
To start the Radalert 50, set the top switch to the mode you want, and set the bottom
switch to On or Audio. The Radalert 50 then does a three-second system check,
displaying all the indicators and numbers.
After the system check, the radiation level is displayed in the selected mode. In
mR/hr and CPM mode, the display shows the accumulated reading for the first
minute, with the hourglass icon to show that the first minute's reading is not yet
complete. One minute after you start the Radalert 50, the hourglass disappears.
Operating Modes
When the mode switch is set to mR/hr or CPM, the numeric display is updated every
minute.
CPM and total counts are the most direct methods of measurement; mR/hr is
calculated using a conversion factor optimized for Cesium-137, so this mode is less
accurate for other radionuclides. It is more appropriate to measure alpha and beta
activity using CPM than using mR/hr. Conversion for alpha and beta emitters is
calculated differently, and the Radalert 50's reading in mR/hr may not be accurate.
The most immediate indicators of the radiation level are the count light, the audio
beep, and the alert. An increase is not shown on the numeric display in CPM and
mR/hr modes until the end of a full minute.
6
Operating Ranges
The following table shows the radiation levels the Radalert 50 measures in each
mode and how they are displayed. When radiation levels increase over certain
preset levels, the Radalert 50 uses autoranging, automatically changing to the
X1000 scale. Whenever X1000 is shown above the numeric display, multiply the
displayed reading by 1000 to determine the radiation level.
Mode Normal Range X1000 Range
mR/hr .001-50 NA
CPM 0-9999 10,000-50,000
(displayed as 10.00-50.00, with
X1000 indicator)
Total 0-9999 10,000-60,000
(displayed as 10.00-60.00, with
X1000 indicator)
Maximum level. When the maximum level for the current mode is reached, the
numeric display remains at the maximum level and a small arrow is shown at the
bottom right of the display.
Taking a Total Count
When the mode switch is set to Total, the Radalert 50 starts totaling the counts it
registers, and the numeric display is updated each time a count is registered.
A total count is useful for determining the average counts per minute over a period of
time. The number of counts detected by the Radalert 50 varies from minute to
minute due to the random nature of radioactivity. When a count is taken over a
longer period, the average count per minute is more accurate, and any small
increase is more significant.
Taking an average allows you to detect low-level contamination or differences in
background radiation due to altitude or soil mineral content, and can be useful for
educational purposes. For example, if one 10-minute average is one count higher
than another 10-minute average, the increase may be due to normal variation. But
over 12 hours, a one-count increase over the 12-hour background average is
statistically significant.
7
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