Ludlum Measurements 25 User manual

LUDLUM MODEL 25 AND 25-1
PERSONAL RADIATION MONITOR
USER’S MANUAL
October 2014
Serial Number 25000100 and Succeeding
Serial Numbers

LUDLUM MODEL 25 AND 25-1
PERSONAL RADIATION MONITOR
USER’S MANUAL
October 2014
Serial Number 25000100 and Succeeding
Serial Numbers

Model25and25-1PersonalRadiationMonitor User’s Manual
Table of Contents
Introduction 1
Getting Started 2
Unpacking and Repacking 2-1
Battery Installation 2-1
Instrument Operational Test 2-1
Instrument Use and Controls 2-3
Distinguishing ALERTs and ALARMs 2-6
Specifications 3
Calibration and Changing Parameters 4
Calibration Overview 4-1
Entering SETUP Mode and Changing Parameters 4-2
Calibration Procedure 4-3
Safety Considerations 5
Environmental Conditions for Normal Use 5-1
Warning Markings and Symbols 5-1
Cleaning and Maintenance Precautions 5-2
Revision History 6
Recycling 7

Model25and25-1PersonalRadiationMonitor User’s Manual Section1
Ludlum Measurements, Inc. Page 1-1 March 2014
Introduction
he Model 25 and 25-1 is a personal radiation detection and
warning instrument. The instrument features a large backlit LCD
(liquid crystal display), a bright (daylight-visible) warning light, and
a piercing audio warning. The unit body is made of lightweight
but durable plastic and can survive brief immersion in water. The Model 25
may be clipped to a belt or worn around the neck with a lanyard.
The Model 25-1 readout is in mSv/h or Sv/h, whereas the Model 25
readout is in mR/hr or R/hr. This being the only difference between the
two, this manual will refer to the two instruments as “Model 25.”
The detector inside the Model 25 measures gamma radiation up to 999
R/hr (9.99 Sv/h). The display, which normally shows exposure rate, will
also display total accumulated dose, and time remaining. In an alarm
situation, the display (automatically backlit if light levels are dim) rotates
every two seconds among the three displays: exposure rate, accumulated
dose, and time remaining. Thus, in an emergency situation, a responder can
be warned of the radiation level and informed of the time remaining before
their maximum allowed dose is reached.
Setup of the instrument is accomplished also through the front-panel
buttons. The advanced user or administrator can set ALERT and ALARM
levels (both exposure rate and accumulated dose), change calibration
parameters, and zero the total accumulated dose within the setup routine.
The unit is operated with two coin cell batteries for operation from -40 to
65 °C (-40 to 150 °F). Battery life should be approximately 6000 hours
under non-alarming conditions. A low-battery indicator on the LCD warns
when less than eight hours of battery life remain.
T
Sectio
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Getting Started
Unpacking and Repacking
Remove the calibration certificate and place it in a secure location. Remove
the instrument and accessories (lanyard, case, etc.) and ensure that all of the
items listed on the packing list are in the carton. Check individual item serial
numbers and ensure calibration certificates match. The Model 25 serial
number is located on the back panel below the battery compartments.
To return an instrument for repair or calibration, provide sufficient
packing material to prevent damage during shipment.
Every returned instrument must be accompanied by an Instrument
Return Form, which can be downloaded from the Ludlum website at
www.ludlums.com. Find the form by clicking the “Support” tab and
selecting “Repair and Calibration” from the drop-down menu. Then
choose the appropriate Repair and Calibration division where you
will find a link to the form.
Battery Installation
Open each battery lid by using a large coin or screwdriver to unscrew
(counter-clockwise) the two round battery holders on the back of the
instrument. Remove the two old batteries, and replace with new batteries.
Ensure that both batteries have the plus (+) sign facing outwards. Screw
each battery holder clockwise until the holder is flush with the case. Battery
replacement may be done by the user, and is not considered a reason for
recalibration.
Instrument Operational Test
Turn the instrument ON by pressing the ON/ACK button for about a
second, and then releasing. The instrument should activate all the LCD
segments, the audio, and the warning light. It then displays a version
number before displaying the current exposure rate, normally 0.0 mR/hr (or
.000 mSv/h.
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Ensure that the low-battery indicator is not present. If the low-battery
indicator is present, replace the batteries as soon as possible. Under
extremely low battery conditions, be aware that the unit may not even turn
on, or may turn itself off abruptly.
If possible, expose the detector to a source of radiation. Small check sources
of radiation are available from Ludlum Measurements. While exempt from
many regulations because of their small size, these sources are large enough
to produce a response on this instrument. The detector's position is marked
by the small plus (+) sign on the front panel of the Model 25. A typical 1
µCi (37 kBq) 137Cs check source will produce an exposure rate of
approximately 3 mR/hr (.003 mSv/h). If this procedure is done routinely
with the same radiation source, instrument malfunction may be detected
when anomalous readings are observed.
A reference reading with a check source should be obtained at the time of
calibration or at the time the instrument is received in the field. If at any
time the instrument fails to read within 20% of the reference reading when
using the same check source, it should be sent to a calibration facility for
recalibration and/or repair.
Note that the Model 25 has its own diagnostic tests to ensure that the
detector is functioning correctly. The Model 25 can detect when the
radiation detector is malfunctioning and will flash “0.0 mR/hr” (.000
mSv/h) with “F,” the warning audio, and the light to indicate a detector
malfunction. If this indication is observed, remove the unit from service
and have it evaluated by a qualified repair and calibration technician.
Once this procedure has been completed, the instrument is ready for use.

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Instrument Use and Controls
With only two front-panel buttons, the Ludlum Model 25 is simple and easy
to use with minimal training required. Under typical use, the display shows
just the current exposure rate. Whenever the MODE button is pressed, or
during an ALERT or ALARM condition, the display rotates among the
exposure rate, the total accumulated dose, and the time remaining (in
hh:mm format). The additional display modes may help the user to decide
how long to stay in a high-radiation area.
See the Model 25 front-panel drawing at the beginning of this manual
to reference the following two controls:
ON/ACK button: Used to power the Model 25 ON and OFF, and
acknowledge audio on alerts and alarms.
ON: Press for approximately one second and release (all LCD
segments will activate, and firmware version will be shown).
OFF: Press for approximately five seconds (audio will beep and
LCD will clear).
ACK (acknowledge): Will silence audio during an ALERT or
ALARM condition, but in an ALARM condition the audio will
continue to be activated once every 60 seconds to remind the user.
MODE button: When pressed under non-alarm conditions, the display
rotates between the total accumulated dose, the time remaining, and back to
the normal exposure rate display. If the light is very dim, pressing the
MODE button will also turn on the backlight while the display cycles
among the three display modes.
The Exposure Rate (main active screen) at typical background radiation
levels shows a number similar to 0.04 mR/hr. Figure 1 (on the following
page) also shows the low-battery icon.

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Figure 1: The Exposure Rate Screen shows typical background radiation rate and the low-
battery icon.
Zeroing Accumulated Dose: In order to “zero” the accumulated dose, the
user must enter the setup mode, and then not press any other buttons. The
parameters will change every four seconds, and the unit will return
automatically to the normal mode after the last parameter is presented. The
accumulated dose has now been reset to zero.
The Accumulated Dose screen is shown in Figure 2. 80.5 R is a significant
dose, and thus Figure 2 also shows the ALARM indication.
Figure 2: Accumulated Dose Screen with ALARM indicator