LUDLUM MODEL 2241-2 User manual

LUDLUM MODEL 2241-2
SURVEY METER
January 2016
Serial Number 237627 and Succeeding
Serial Numbers

LUDLUM MODEL 2241-2
SURVEY METER
January 2016
Serial Number 237627 and Succeeding
Serial Numbers

STATEMENT OF WARRANTY
Ludlum Measurements, Inc. warrants the products covered in this manual to be free of
defects due to workmanship, material, and design for a period of twelve months from the
date of delivery. The calibration of a product is warranted to be within its specified
accuracy limits at the time of shipment. In the event of instrument failure, notify Ludlum
Measurements to determine if repair, recalibration, or replacement is required.
This warranty excludes the replacement of photomultiplier tubes, G-M and proportional
tubes, and scintillation crystals which are broken due to excessive physical abuse or used
for purposes other than intended.
There are no warranties, express or implied, including without limitation any implied
warranty of merchantability or fitness, which extend beyond the description of the face
there of. If the product does not perform as warranted herein, purchaser’s sole remedy
shall be repair or replacement, at the option of Ludlum Measurements. In no event will
Ludlum Measurements be liable for damages, lost revenue, lost wages, or any other
incidental or consequential damages, arising from the purchase, use, or inability to use
product.
RETURN OF GOODS TO MANUFACTURER
If equipment needs to be returned to Ludlum Measurements, Inc. for repair or calibration, please send to
the address below. All shipments should include documentation containing return shipping address,
customer name, telephone number, description of service requested, and all other necessary information.
Your cooperation will expedite the return of your equipment.
LUDLUM MEASUREMENTS, INC.
ATTN: REPAIR DEPARTMENT
501 OAK STREET
SWEETWATER, TX 79556
800-622-0828 325-235-5494
FAX [phone]

Ludlum Measurements, Inc. January 2016
Table of Contents
Introduction 1
Getting Started 2
Unpacking and Repacking 2-1
Battery Installation 2-1
Operational Check 2-2
Specifications 3
Instrument 3-1
Removable Switchboard Adjustable Parameters 3-2
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 Considerations 5
Environmental Conditions for Normal Use 5-1
Detector Connector 5-1
Warning Markings and Symbols 5-1
Maintenance 6
Recalibration 6-1
Batteries 6-2
Technical Theory of Operation 7
Main Board 7-1
Switch Board 7-3
Display Board 7-3
Instrument Setup 8
Entering or Changing Switch Board Parameters 8-1

Model2241-2 TechnicalManual
Ludlum Measurements, Inc. January 2016
The Function Switch 8-1
Function Switch Position Descriptions and Variables 8-2
Loading Default Parameters 8-6
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
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
Drawings and Diagrams 11
RS-232 Output Formats - Appendix A A
Binary Output Format A-1
ASCII Output Format A-4

Model2241-2 TechnicalManual Section1
Ludlum Measurements, Inc. Page 1-1 January 2016
Introduction
he Model 2241-2 is a portable microprocessor-based digital scaler/
ratemeter designed for use with scintillation, Geiger-Mueller
(GM), and proportional type detectors to measure ionizing
radiation. 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) are represented in
either 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 to1 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.
Other features include Dead Time Correction (DTC) to compensate for
detector dead time; audible click-per-event with programmable 1, 10, 100,
and 1000 divide-by; LCD backlight with programmable ON time;
programmable fixed or variable response time; and count overflow visual
alarm, indicating that the counting circuitry is nearing the maximum
counting capability.
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Model2241-2 Technical Manual Section 1
Ludlum Measurements, Inc. Page 1-2 January 2016
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 400 to 2400 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.

Model2241-2 Technical Manual Section 2
Ludlum Measurements, Inc. Page 2-1 January 2016
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 are therefore, 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.
Every 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
Ensure the OFF/SCALER/RATEMETER switch is in the OFF position. Open
the battery lid by turning the quarter-turn thumb screw counterclockwise
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Model2241-2 Technical Manual Section 2
Ludlum Measurements, Inc. Page 2-2 January 2016
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-turn). The diagram to the left illustrates how
this is done. Next, place the DETECTOR SELECTOR switch in the appropriate
position.
Turn the OFF / SCALER / RATEMETER switch to the RATEMETER position.
Notice that the display goes through an initialization sequence. The display
will show all 8s 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 (00.0 µR/hr, for example) should
be shown. When switched to the SCALER position, a single 0 will
be displayed.
The display will auto-range to the current level (see figure at left). When
auto-ranging down, the Model 2241-2 uses multiples of 5. This technique
keeps the decimal point from jumping between numbers when
viewing values around multiples of 10.
Check for a proper background reading:
If using a Ludlum Model 44-9 detector, a typical
reading would be 25-50 cpm or 8-15 µR/hr.
If using a Ludlum Model 44-2 detector, a typical reading
would be 1.4-2.6 kcpm or 8-15 µR/hr.
A reference reading (or readings) with a check source should be obtained
with the detector(s) in a constant and reproducible manner at the time of