Keison Digilert 100 Installationshandbuch
3/06
Nuclear Radiation Monitor
Operation Manual
Contents Page
1 Introduction 1
How the Digilert 100 Detects Radiation 1
2 Features 1
The Display 3
The Switches 3
The Detector 4
The Ports 5
3 Operation 5
Units of Measurement 5
Starting the Digilert 100 5
Operating Modes 6
Operating Ranges and Response Times 6
Taking a Timed Total Count 7
Using the Alert 8
The Utility Menu 9
Interfacing to an External Device 10
4 Common Procedures 10
Establishing the Background Count 11
Environmental Area Monitoring 11
Checking an Object 11
5 Maintenance 12
Calibration 12
Troubleshooting 15
6 Basics of Radiation and Its Measurement 16
Ionizing Radiation 17
Measuring Radiation 18
Radiation Measurement Units 18
Determining What Is a High Reading 19
Contents Page
Appendix A Technical Specifications 20
Appendix B Options 21
Observer Software 22
Warranty 23
Calibration Database Application 24
Precautions
To keep the Digilert 100 in good condition, handle it with care, and
observe the following precautions:
* Do not contaminate the Digilert 100 by touching it to radioactive
surfaces or materials.
* Do not leave the Digilert 100 in temperatures over 122* F (50
C) or in direct sunlight for extended periods of time.
* Do not get the Digilert 100 wet. Water can damage the circuitry
and the coating of the mica surface of the Geiger tube.
* Avoid making measurements with the detector window in direct
sunlight; this could affect the readings if the coating of the mica
surface of the Geiger tube has been damaged by moisture or
abrasion.
* Do not put the Digilert 100 in a microwave oven. It cannot
measure microwaves, and you may damage it or the oven.
* If you expect to not use the Digilert 100 for longer than one
month, remove the battery to avoid damage from battery
corrosion.
* Change the battery promptly when the battery indicator appears
on the display.
1
1 Introduction
The Digilert™ 100 is a health and safety instrument that measures alpha, beta,
and gamma radiation. With the Digilert 100, 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 Digilert 100 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 Digilert 100 to a computer or data logger to record and
tabulate your data
This manual gives complete instructions for using the Digilert 100 and
procedures for common applications.
How the Digilert 100 Detects Radiation
The Digilert 100 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 Digilert 100 displays the counts in the mode you
choose: counts per minute (CPM), milliroentgens per hour (mR/hr), or total
counts for a timed period. In SI units, counts per second (CPS) and
microsieverts per hour ( μSv/hr) are used.
2 Features
The Digilert 100 measures alpha, beta, gamma, and x-ray radiation. This
chapter briefly describes the Digilert 100's functions. For more information on
how to use the Digilert 100, see Chapter 3, "Operation."
The Digilert 100 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.
Whenever the Digilert 100 is operating, the red count light (1) flashes each time
a count (an ionizing event) is detected.
The Display
Several indicators on the LCD (1)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.
2
(1) LCD Display
(8) CAL Input
(7) Count Light (3) On/Off/Audio
Switch
(2) Mode Switch
(9) Output
(5) Plus & Minus Buttons
(4) Set Button
Illustration 1
Illustration 2
" A radiation symbol (C)
appears when the Alert feature is on.
" An hourglass (D) appears to the left of the numeric display during a timed
count.
" TOTAL (E) appears when the Digilert 100 is in Total mode.
" X1000 (F) appears when the radiation level is displayed in X1000 mode.
" CAL (G) appears while you are calibrating the Digilert 100.
" SET (H) appears when you are setting the timer, the Alert level, or the
calibration factor, or working in the Utility menu (the numeric display shows
the setting you are adjusting instead of the current radiation level).
" The current unit of measurement (I)- CPM, CPS, mR/hr or μSv/hr--is
displayed to the right of the numeric display.
" MENU (J) appears when you are in the Utility Menu.
The Switches
The Digilert 100 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 (3)
Audio. The Digilert 100 is on, and it makes a clicking sound for each radiation
event detected.
On. The Digilert 100 is operating, but audio is off.
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(A) Numeric Display
(B) Low Battery
(C) Alert
(D) Timer
(E) Total
Mode
(I) Units of
Measurments
(H) Utility Menu, Timer,
Calibation, Alarm
Set Mode
(G) CAL
Mode
(F) X1000
Mode
(J) Menu
Illustration 3
Off. The Digilert 100 is not operating.
Mode Switch (2)
mR/hr. The numeric display shows the current radiation level in milliroentgens
per hour from .001 to 110. When SI units are used, it shows the current
radiation level in microsieverts per hour, from .01 to 1100.
CPM. The display shows the current radiation level in counts per minute from 0
to 350,000. When X1000 is shown, multiply the numeric reading by 1000 to get
the complete reading. When SI units are used, the display shows the current
radiation level in counts per second from 0 to 3,500.
Total. The display shows the accumulated total of counts starting when the
switch is turned to this position, from 0 to 9,999,000. When X1000 is shown,
multiply the numeric reading by 1000 to get the complete reading.
Set Button (Figure 2 (4))
The Set button is used to set the alert, select items in the Utility Menu, and
set the Calibration settings. See “Using the Alert” and “Utility Menu” in
Chapter 3 and “Calibration” in Chapter 5.
+ and - Buttons (Figure 2 (5))
The “+” and “-” buttons are used to adjust the numeric display for timed
counts, alert settings, and calibration settings. See “Taking a Timed Count”
and “Setting the Alert” in Chapter 3 and “Calibration” in Chapter 5.
The “+” and “-” buttons can also be used to make selections in the “Utility
Menu”. For details, see “Utility Menu” in Chapter 3.
The Detector
The Digilert 100 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 Digilert 100 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.
4
The Ports
There are two ports on the left side of the Digilert 100.
The calibration input port (2) is used for calibrating electronically using a pulse
generator. For more information, see "Calibrating Electronically" in Chapter 5.
The output port (3) below the calibration input port allows you to interface the
Digilert 100 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.
3 Operation
The guidelines in this chapter describe how to use the Digilert 100.
Units of Measurement
The Digilert 100 is designed both for users of conventional units (milliroentgens
per hour and counts per minute) and for users of SI units (microsieverts per
hour and counts per second). To switch between conventional and SI units, use
the Utility Menu. See "The Utility Menu" in this chapter.
Starting the Digilert 100
Be sure that a standard 9-volt alkaline battery is installed in the battery
compartment in the lower rear of the Digilert 100. Note: When installing the
battery, place the battery wires along the side of the battery and not under it.
To start the Digilert 100, set the top switch to the mode you want, and set the
bottom switch to On or Audio. The Digilert 100 then does a four-second system
check, displaying all the indicators and numbers.
After the system check, the radiation level is displayed in the selected mode.
One minute after you start the Digilert 100, a short beep indicates that enough
information has been collected to ensure statistical validity.
Operating Modes
5
When the mode switch is set to mR/hr or CPM, the numeric display is updated
every three seconds. At low count rates, significant changes in the radiation
level displayed can take up to one minute to stabilize. See "Operating Ranges
and Response Times" in this chapter for more information.
CPM (or CPS) and timed total counts are the most direct methods of
measurement; mR/hr (or μSv/hr) is calculated using a conversion factor
optimized for Cesium-137, so this mode is less accurate for other radionuclides,
unless you have calibrated the Digilert 100 for a specific radionuclide using an
appropriate source. 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 Digilert 100'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. It takes three seconds before an increase is shown
on the numeric display in the dose rate modes.
Operating Ranges and Response Times
The following table shows the radiation levels the Digilert 100 measures in each
mode and how they are displayed. In some modes, when radiation levels
increase over certain preset levels, the Digilert 100 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 Regular Range X1000 Range
mR/hr .001-110 NA
μSv/hr .01-1100 NA
CPM 0-9999 10,000-350,000
(displayed as 10.00-350, with X1000 indicator)
CPS 0-3500 NA
Total/Timer 0-9999 10,000-9,999,000
(displayed as 10.00-9999, with X1000 indicator)
Maximum level. When the maximum level for the current mode is reached, the
6
Digilert 100 beeps for three seconds, pauses for three seconds, and repeats
that pattern. The numeric display flashes. The beeping pattern and the flashing
continue until the level decreases or the Digilert 100 is turned off.
Display update and response time. In Total mode, the numeric display is
updated each second. In the dose rate modes, the numeric display is updated
every three seconds. When the radiation level is less than 1,000 CPM, the
reading in any of the dose rate modes is based on the radiation detected in the
immediately previous minute. In order to give a quicker response to changes,
when the radiation level exceeds 1,000 CPM, the reading is based on the
previous 3 seconds, as shown in the following table. This automatic change in
response time is called auto averaging.
Radiation level Basis for reading
<1000 CPM or 1 mR/hr 1 minute
>1000 CPM or 1 mR/hr 3 seconds
Note: You can set the response time to 3 seconds at all radiation levels using
the Utility Menu; see "The Utility Menu" in this chapter.
Taking a Timed Total Count
The Digilert 100 can give you a total count for a timed period of from one minute
to 24 hours.
A timed total count is useful for determining the average counts per minute over
a period of time. The number of counts detected by the Digilert 100 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.
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