Ludlum Measurements 2241-2RK User manual

LUDLUM MODEL 2241-2RK
RESPONSE KIT
July 2012
Serial Number 237627 and Succeeding
Serial Numbers

LUDLUM MODEL 2241-2RK
RESPONSE KIT
July 2012
Serial Number 237627 and Succeeding
Serial Numbers

Ludlum Measurements, Inc. July 2012
Table of Contents
Introduction 1
Getting Started 2
Unpacking and Repacking 2-1
Battery Installation 2-1
Operational Check 2-2
Survey Techniques 2-4
Specifications 3
Identification of Controls and Functions 4
Display 4-1
Display Status Definitions 4-1
Front Panel Controls 4-2
Front Panel Calibration Controls 4-3
Main Board Controls 4-4
Switch Board Controls 4-5
Safety & Maintenance Considerations 5
Environmental Conditions for Normal Use 5-1
Detector Connector 5-1
Warning Markings and Symbols 5-1
Maintenance 5-2
Operational Check 5-3
Recalibration 5-3
Batteries 5-3
Detector Model 44-9 Tube Replacement Procedure 5-4
Radiation Basics 6
Radiation and Life 6-1
The Unstable Atom 6-2
Radioactive Decay 6-3
Ionizing Radiation 6-4
Measuring Ionizing Radiation 6-5
What are the Health Risks from Ionizing Radiation? 6-6
How Much Ionizing Radiation is Dangerous? 6-7

Model 2241-2RK Technical Manual
Ludlum Measurements, Inc. July 2012
Background Radiation 6-10
Manmade Radiation 6-11
Protection from Radiation 6-11
Standards and Regulation 6-12
Who is in Charge? 6-12
Technical Principle of Operation 7
Main Board 7-1
Switch Board 7-3
Display Board 7-3
Instrument Setup & Calibration 8
Factory Settings 8-1
Entering or Changing Switch Board Parameters 8-1
The Function Switch 8-2
Function Switch Position Descriptions and Variables 8-2
Calibration 8-7
General Detector Setup Information 8-8
Counts per minute (C/m) Calibration 8-9
R/hr Calibration 8-11
Determining CC and DTC 8-12
Detector Overload (OVL) Calibration 8-19
Loading Default Parameters 8-20
Software License Agreement 8-21
Recycling 9
Parts List 10
Model 2241-2 Survey Meter 10-1
Main Circuit Board, Drawing 408 × 223 10-1
Calibration Board, Drawing 408 × 127 10-3
Display Board, Drawing 408 × 259 10-4
Switch Board, Drawing 408 × 45 10-5
Chassis Wiring Diagram, Drawing 408 × 131 10-5
Model 44-9 Alpha-Beta-Gamma Detector (Pancake) 10-7
Model 44-2 Gamma Scintillator 10-7
Drawings 11

Model 2241-2RK Technical Manual Section1
Ludlum Measurements, Inc. Page 1-1 July 2012
Introduction
he Model 2241-2RK is a first-responder kit that includes a portable
microprocessor-based digital Scaler/ Ratemeter, as well as
scintillation and Geiger-Mueller (GM) type detectors. It is designed
for the rugged use of first responders in the measuring of ionizing
radiation. A rugged waterproof airtight carrying case with foam insert, check
source with holder, and detector cable are provided.
The Instrument
Data is presented on a four-digit (six digits in the Scaler mode) Liquid
Crystal Display (LCD) with moving decimal point. A three-position switch
labeled ˝OFF/RATEMETER/SCALER˝ selects the desired operating mode for
the instrument. A locking toggle switch labeled ˝DET 1 and DET 2˝allows for
quick change of operating parameters when changing out detectors.
Programmable display units (˝RATEMETER˝mode only) can be represented
in 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.
Section
1
T

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Ludlum Measurements, Inc. Page 1-2 July 2012
Other features include: 1) Dead Time Correction (DTC) to compensate for
detector dead time, 2) audible click-per-event with programmable 1, 10, 100,
and 1000 divide-by; 3) LCD backlight with programmable ON time, 4)
programmable fixed or variable response time, and 5) count overflow visual
alarm, indicating that the counting circuitry is nearing the maximum
counting capability.
All of the features described above may be programmed manually using the
internal switch board or by computer through the RS-232 port. Two
different detector operating parameters may be stored in non-volatile
memory. The switch board can be removed after entering or changing
parameters to prevent tampering with setup parameters.
A regulated high-voltage power supply and two independent set-point
controls adjustable from 200 to 2500 volts with detector overload detection
and adjustable discrimination levels add versatility to the instrument. This
supports operation for a broad range of detectors and connecting cable
lengths. All of the calibration controls are covered to prevent any inadvertent
adjustment to the detector operating parameters.
The instrument is powered by two standard ˝D˝cell batteries. The unit body
is made of cast-and-drawn aluminum with beige powder coating, which aids
in the decontamination of surfaces.
The Detectors
The Response Kit’s GM (Geiger-Mueller) Pancake Detector, Model 44-9,
will detect alpha, beta, and gamma radiation. Its size and shape provide easy
handling for surveying or personnel monitoring. The detector is energy
dependant, over-responding by a factor of 6 (to gamma radiation) in the 60
keV–100 keV range when normalized to 137
The Model 44-9 operates at 900 volts. The recommended
instrument input sensitivity (set at calibration) is
approximately 30 ±10 mV to prevent the detector from double pulsing.
Cs. The
response of this detector is nominally linear (within 10%)
from 1 mR/hr to 300 mR/hr.
The thin mica window in this detector is protected by a 79% open stainless
steel screen. The GM tube can be easily removed for replacement if
necessary. The GM tube face may rupture above 8000 feet altitude pressure.
Consequently, tube failure is likely if transported above this altitude in an
aircraft not pressurized.

Model 2241-2RK Technical Manual Section1
Ludlum Measurements, Inc. Page 1-3 July 2012
The Response Kit’s sodium iodide (Nal) gamma scintillator, Model 44-2, is
used for the detection of low-level gamma radiation, in the range of 50 keV-
1.5 MeV. The detector is energy dependant, over-responding
by a factor of 10 or greater in the 100 keV range, and under-
responding by a factor of 0.5 above 1 MeV when normalized to
137Cs. The response of this detector is nominally linear (within
10%), from 5 µR/hr to 50 mR/hr.
This detector consists of a one-inch (2.54 cm) diameter by one-inch thick,
Nal crystal, coupled to a photomultiplier tube, and is housed in 0.16 cm
(0.062 in.) thick aluminum housing. Recommended instrument sensitivity is
approximately 10mV or higher. Operating voltage varies from one detector
to another.
Common applications for this detector include background radiation
monitoring and low-level radiation detection.

Model 2241-2RK Technical Manual Section2
Ludlum Measurements, Inc. Page 2-1 July 2012
Getting Started
Unpacking and Repacking
Remove the calibration certificates and place them in a secure location.
Remove the instrument, detectors, and accessories (batteries, cable, 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 2241-2 serial number is located on the front panel below the battery
compartment. Most Ludlum Measurements, Inc. detectors have a label on
the base or body of the detector for model and serial number identification.
Important!
If multiple shipments are received, ensure that the detectors
and instruments are not interchanged. Each instrument is
calibrated to specific detectors and is not interchangeable.
To return an instrument for repair or calibration, provide sufficient packing
material to prevent damage during shipment. Also provide appropriate
warning labels to ensure careful handling. Include detector(s) and related
cable(s) for calibration. Include brief information as to the reason for return,
as well as return shipping instructions:
- Return shipping address
- Customer name or contact
- Telephone number
- Description of service requested and all other necessary
information
Battery Installation
Ensure the OFF/SCALER/RATEMETER switch is in the OFF position. Open
the battery lid by turning the quarter-turn thumb screw counterclockwise
Section
2

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Ludlum Measurements, Inc. Page 2-2 July 2012
Install two ˝D˝size batteries in the compartment. Note the (+) and (–)
marks inside the battery door. Match the battery polarity to these marks.
Close the battery box lid.
Note:
The center post of a “D” size battery is positive.
Operational Check
Connect a detector to the Model 2241-2 by using the cable provided; firmly
pushing the connectors together while twisting clockwise until the connector
latches (one quarter of a turn). The diagram to the left illustrates how this is
done. Next, place the DETECTOR SELECTOR switch in the appropriate
position.
Note:
The Model 2241-2 front panel (when part of a response kit)
includes a color code at the detector selector switch, which
corresponds to color coded detectors included in the kit. This
serves as a reminder (quick reference) of the set detector
parameters for each position. See Section 8, Subsection
“Factory Settings,” (Page 8-1) for the color code.
Turn the OFF/SCALER/RATEMETER switch to the RATEMETER
position. Notice that the display goes through an initialization
sequence. The display will show all “8”s with decimal points. Check
to make sure all segments display, as illustrated in the diagram to the
left.
The LCD then displays the firmware number in the format “P-XX
YY.” The “XX” is the firmware number, and the “YY” is the
firmware version. (The figure to the left is for example only; to
illustrate location of display.)
The minimum displayable value (for example 00.0 µR/hr) should be
shown. When switched to the SCALER position, a single “0” will be
displayed.