Ludlum Measurements 2242 User manual

LUDLUM MODEL 2242
SURVEY METER
November 2010
Serial Number 219764 and Succeeding
Serial Numbers

LUDLUM MODEL 2242
SURVEY METER
November 2010
Serial Number 219764 and Succeeding
Serial Numbers
LUDLUM MEASUREMENTS, INC.
501 OAK STREET, P.O. BOX 810
SWEETWATER, TEXAS 79556
325-235-5494, FAX: [phone]

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. November 2010
Table of Contents
Introduction 1
Getting Started 2
Unpacking and Repacking 2-1
Battery Installation 2-1
Operating the Instrument 2-2
Principle of Operation 2-2
Specifications 3
Description of Controls and Functions 4
Operator Controls 4-1
Internal Controls 4-2
Display 4-3
Safety & Maintenance Considerations 5
Environmental Conditions for Normal Use 5-1
Cleaning Instructions and Precautions 5-1
Warning Markings and Symbols 5-1
Maintenance 5-2
Recalibration 5-3
Batteries 5-3
Setup and Calibration 6
Entering or Changing Switch Board Parameters 6-1
The Function Switch 6-1
Function Switch Position Descriptions and Variables 6-2
Calibration 6-4
General Detector Setup Information 6-4
Exposure Rate Calibration 6-4
Detector Overload (OVL) Calibration 6-5
Loading Default Parameters 6-6

MODEL 2242 Technical Manual
Ludlum Measurements, Inc. November 2010
Troubleshooting 7
Technical Principle of Operation 8
Recycling 9
Parts List 10
Model 2242 Survey Meter 10-1
Main Board, Drawing 408 × 223 10-1
Calibration Board, Drawing 408 × 229 10-3
Display Board, Drawing 408 × 79 10-4
Switch Board, Drawing 408 × 46 10-4
Wiring Diagram, Drawing 408 × 221 10-5
Drawings and Diagrams 11

MODEL 2242 Technical Manual Section1
Ludlum Measurements, Inc. Page 1-1 November 2010
Introduction
he Model 2242 is a portable microprocessor-based digital Ratemeter
designed for detection and measurement of ionizing radiation. The
data is presented on a 4-digit Liquid Crystal Display (LCD). A 3-
position switch labeled “OFF/LOW (mR/h)/HIGH (R/hr)” selects
the desired operating range for the instrument. The internal detectors are
energy-compensated GM (Geiger-Mueller) tubes capable of measuring fields
from 0.01 mR/hr to 999.9 R/hr.
This instrument incorporates independent adjustable alarms for each range.
The first-level alarm is indicated by ALERT on the LCD. Display of ALARM
on the LCD, a continuous audible tone and an illuminated alarm LED (red)
indicate the second-level alarm. Both audible alarms can be silenced
(acknowledged) by depressing the RESET switch.
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.
All of the features described above may be programmed manually, using the
internal switch board, or by computer through the RS-232 port. The switch
board can be removed after entering or changing parameters to prevent
undesired altering of setup parameters.
A regulated high voltage power supply, dual set points adjustable from 400
to 2500 volts, with detector overload detection add versatility to the
instrument. A single adjustable discrimination setting applies to both internal
detectors. All calibration controls are covered to prevent any inadvertent
altering of the detector operating parameters.
Section
1
T

MODEL 2242 Technical Manual Section1
Ludlum Measurements, Inc. Page 1-2 November 2010
The instrument operates on two ˝D˝cell flashlight batteries. The unit body
is made of cast-and-drawn aluminum and is covered in beige powder-
coating to aid in surface decontamination.

MODEL 2242 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-1 November 2010
Getting Started
Unpacking and Repacking
Remove the calibration certificate and place it in a secure location. Remove
the instrument and accessories (batteries, cables, 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 2242
serial number is located on the front panel below the battery compartment.
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 that the range selector switch is in the ˝OFF˝position. Open the
battery lid by pushing down and turning the quarter-turn thumbscrew
counterclockwise ¼ turn. 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, push down and turn the
quarter-turn thumb screw clockwise ¼ turn.
Note:
Center post of a flashlight battery is positive. The batteries are
placed in the battery compartment in opposite directions.
Section
2

MODEL 2242 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-2 November 2010
Operating the Instrument
Turn the OFF/LOW(mR/hr)/HIGH(R/hr) switch to the
LOW(mR/hr) position. The display goes through an
initialization sequence. The display will show all “8”s
with decimal points. Check to make sure all segments are
on, as illustrated to the left.
The LCD then shows the firmware number in the
format “P-XX YY.” The “XX” is the firmware number,
and the “YY
Select the desired AUD ON/OFF parameter and proceed
to use instrument. Switch up to the R/hr range only if the
OFLOW and/or OVERLOAD symbols are displayed, or if
the display shows 999 mR/hr.
” is the firmware version. (The figure to the
left is for example only, to illustrate location of display.)
Principle of Operation
The Model 2242 utilizes microprocessor-based technology, providing an
extensive range of operating features. Two independent detector parameters
can be stored in memory (with the exception of a single discrimination
parameter).
The Model 2242 incorporates a detachable switch board used to program
detector and operating parameters into non-volatile memory (retains the
data even after the power is removed). The switch board may be removed so
that the operating parameters cannot be altered. If multiple units are to be
used at one location, fewer Switch Boards may be purchased in order to
program all instruments. A 16-position rotary switch (FUNCTION) selects
each of the 16 operating/detector parameters. Three pushbutton switches
on the Switch Board provide the means to change and save the variables for
each of the parameters.
An RS-232 port is also available via the switch board for computer
connection. An optional can with the RS-232 connector mounted externally
is also available. Communication baud rate may be set with the FUNCTION
switch to correspond to the computer baud. The computer can adjust the
detector parameters and retrieve data.

MODEL 2242 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-3 November 2010
An LCD provides the readout for the
ratemeter data with the programmed units
and multipliers, as well as ALERT, ALARM,
OVERLOAD and OVERFLOW annunciators,
"low battery" icon, and scaler counting
mode indication (COUNTING – not used). The four 0.5" digits are used for
the ratemeter data. The LCD also displays the variables during the manual
programming sequence. (See figure above.) A front panel alarm LED (red)
illuminates during an alarm condition.

MODEL 2242 Technical Manual Section3
Ludlum Measurements, Inc. Page 3-1 November 2010
Specifications
0
POWER: Two standard "D" size batteries; current drain approx. 35 mA
(backlight off); minimum battery voltage 2.2 ±0.1 Vdc
BATTERY DEPENDENCE: Instrument calibration change less than 3% to
battery endpoint
BATTERY LIFE: Approximately 200 hours with alkaline batteries
WARM-UP TIME: Unit may be used immediately after the LCD
initialization sequence is completed, approximately 5 seconds after turn-
on
DISPLAY: 4-digit LCD with 1.3cm (0.5 inch) character height; 2
additional 0.5cm (0.2 inch) digits are used for the exponential powers
(parameter setup)
Backlight "ON" Time: 5, 15, 30, 60, 90, 120, or 240 ±1 second
MEASURED RANGES:
mR/hr – 0.01 to 999.9
R/hr – 0.01 to 999.9
DISPLAY LINEARITY: Within ±10% of the true value with connected
detector
RESPONSE TIME: Normally the time constant (TC) varies from 1 – 10
seconds
The TC is defined as a one-time constant, which equals 63% of the final
reading. To convert to the 10-90% of final reading definition, the TC
value will have to be multiplied by 2.25; the readout updates every 2
seconds, therefore response time measurements will be rounded to 2-
second intervals; example: fixed TC = 2 seconds × 2.25 = 4.5 seconds for
90% of final reading - it will take 6 seconds before the display (3 each of
2-second intervals) will reach the 90% of final reading value.
Section
3

MODEL 2242 Technical Manual Section 3
Ludlum Measurements, Inc. Page 3-2 November 2010
ALERT/ALARM: Separate visual and audible adjustable alarm points for
both the mR/hr and R/hr ranges
INPUT SENSITIVITY: Adjustable from 2-100 mV; negative pulse
response. Normally set at approximately 90 mV for the internal detectors
HIGH VOLTAGE: Externally adjustable from 400 to 2500 volts; regulated
within ±0.2% at 1000 Vdc; maximum load: 50 µA at 1000 Vdc
CALIBRATION CONSTANT: 0.001 to 280 × 10 9 counts/unit
DETECTOR DEAD TIME COMPENSATION (DTC): Adjustable from 0 to
9999 microseconds
RS-232 PORT: internal 9-pin ˝D˝ type connector with programmable
baud rate from 150 to 19,200 bps. Optional external connector mounted
on can is available.
SIZE: 16.5 x 8.9 x 21.6 cm (6.5 x 3.5 x 8.5 inch), including handle
WEIGHT: 1.6 kg (3.5 lb), including batteries
FINISH: Drawn-and-cast aluminum, with computer-beige powder-coating
and silk-screened nomenclature
ENVIRONMENTAL CONDITIONS FOR NORMAL USE:
Indoor or outdoor use
No maximum altitude
Temperature range of -30° to 50°C (-22° to 122°F)
Maximum relative humidity less than 95% (non-condensing)
Pollution Degree 2 (as defined by IEC 664)

MODEL 2242 Technical Manual Section4
Ludlum Measurements, Inc. Page 4-1 November 2010
Description of Controls and
Functions
Operator Controls
OFF / LOW (mR/hr) / HIGH (R/hr) Switch: A 3-position rotary switch
which applies power to the instrument and selects mR/hr or R/hr
counting modes.
AUD ON/OFF Switch: Front panel toggle switch which silences or enables
the clicks-per-event audio. The audible alarm is independent of the AUD
ON/OFF switch and will override the audible click-per-event. An audible
alarm can only be silenced by depressing the RESET button.
LIGHT (LCD Backlight): When depressed this pushbutton illuminates the
LCD for a pre-programmed time. The backlight ON time can be selected
between 5 and 240 seconds during parameter setup.
RESET Pushbutton: In the non-alarm condition, depressing RESET resets
the ratemeter display to the minimum display readout. In an alarm
condition (ratemeter or scaler), depressing RESET will silence the audible
alarm. Depressing RESET a second time will reset the ratemeter alarm
and/or alert condition. Depressing the scaler count switch located in the
end of the Model 2242 handle resets the scaler alarm only.
Remove the front panel CAL cover to access the following controls:
DISC (Discriminator): A multi-turn potentiometer (approximately 20
revolutions) used to vary the detector pulse counting threshold from 2 to
100 millivolts. A Ludlum Model 500 Pulser or equivalent should be used
in checking or adjusting the pulse discrimination parameter.
OVL (Detector Overload): A multi-turn potentiometer (approximately 20
revolutions) which adjusts the detector current level that must be
exceeded to initiate an OVERLOAD alarm. This control adjusts the current
level discrimination point from 0.5 and 40 microamperes, corresponding
to the specific detector saturation point.
Section
4

MODEL 2242 Technical Manual Section4
Ludlum Measurements, Inc. Page 4-2 November 2010
Note:
Measure the HV at the detector connector with a Ludlum
Model 500 Pulser or a high impedance voltmeter with a high
voltage probe. The impedance of the voltmeter must be 1000
megohms or greater.
HV1 and HV2: Multi-turn potentiometers (approximately 20 revolutions)
used to vary the detector voltage from 400 to 2500 volts. The maximum
HV output is adjusted by the HV LIMIT potentiometer located on the
internal main board. The normal factory settings are 550 Vdc for the
mR/hr range detector and 460 Vdc for the R/hr range detector.
Internal Controls
MAIN BOARD
To access the internal circuit boards, unlatch the latches at each end of the
Model 2242. Carefully separate the top chassis from the bottom cover
(referred to as a ˝can˝). The can has the audio speaker (unimorph) with a 2-
conductor cable attached to the main board. The audio plug may be
disconnected during the internal control adjustments.
HV LIMIT (R027):A multi-turn potentiometer (approximately 20
revolutions) which sets the maximum high voltage limit with the front
panel HV control adjusted to the maximum clockwise position. High
voltage is adjustable from 1250 to 2500 Vdc.
VOLUME (R002):A multi-turn potentiometer (approximately 20
revolutions) which varies audible click-per-event and alarm audio. Adjust
the control to the maximum clockwise position for maximum volume.
Note:
If the VOLUME control is adjusted to the maximum
counterclockwise position the click-per-event or the audible
alarm(s) will not be audible when active.

MODEL 2242 Technical Manual Section4
Ludlum Measurements, Inc. Page 4-3 November 2010
SWITCH BOARD
The switch board utilizes a 16-position rotary switch (“FUNCTION”) to
select the 16 setup parameters. (Refer to schematics and component layout
drawing near the end of the manual.) All setup parameters are stored in the
non-volatile EEPROM, which will retain data even after the Model 2242
batteries are removed. After parameters are entered the switch board can be
removed and the Model 2242 will operate from the programmed
information for the specific detector setup entered prior to the removal of
the board.
Description of and instructions for switch board setup parameters are
detailed in another section of this manual – ˝Initial Instrument Setup˝.
Display
DISPLAY: A 4-digit LCD readout located in the lower right corner of the
display indicates exponential power when in the parameter setup mode.
The upper right of the LCD exhibits units and multiplier(s) - R/hr,
mR/hr, or µR/hr; Sv/h, mSv/h or µSv/h; C/m, kC/m, C/s or
kC/s. The bottom portion of the readout displays ALARM, ALERT,
OFLOW, and OVERLOAD annunciators as well as the "low battery"
icon.
DISPLAY STATUS DEFINITIONS
ALARM - Ratemeter or scaler count has increased above the preset alarm
threshold. An audible continuous tone will accompany the "latching"
ALARM condition. Depressing RESET acknowledges the audible ratemeter
alarm. Depressing RESET a second time will reset the ratemeter reading
and ratemeter alarm.
ALERT - Ratemeter count has increased above the preset alert threshold.
To reset an ALERT condition, depress RESET once if in a non-alarm
condition and twice if in an alarm condition. (The first depression in the
alarm condition acknowledges the audible alarm.) The ratemeter will reset
to the minimum displayable reading each time the alert is reset.
OFLOW (Overflow) - Indicates that the incoming count exceeds the
capability to display stable or reliable readings corresponding to the
radiation level being measured. The overflow symbol will appear when
the ratemeter exceeds 100k cps or if the dead time correction is greater
than 75%.

MODEL 2242 Technical Manual Section4
Ludlum Measurements, Inc. Page 4-4 November 2010
OVERLOAD - Indicates that the detector is being exposed to radiation
intensities greater than the detector maximum operating limit. The
overload alarm point is set by adjusting the OVL control located
underneath the CAL cover.
"low battery" icon - Indicates that the batteries have decreased to the
minimum operating voltage of 2.2 ±0.1 Vdc.

MODEL 2242 Technical Manual Section5
Ludlum Measurements, Inc. Page 5-1 November 2010
Safety & Maintenance
Considerations
Environmental Conditions for Normal Use
Indoor use only
No maximum altitude
Temperature range of –30°C to +50°C (–22°F to 122°F)
Maximum relative humidity of less then 95% (non-condensing)
Pollution Degree 1 (as defined by IEC 664)
Cleaning Instructions and Precautions
The Model 2242 Scaler/Ratemeter may be cleaned externally with a damp
cloth, using only water as the wetting agent. Do not immerse the instrument
in any liquid. Observe the following precautions when cleaning:
1. Turn the instrument range selector switch to the OFF position
and remove the batteries.
2. Allow the instrument to sit for 1 minute before cleaning.
Warning Markings and Symbols
Caution!
The operator or responsible body is cautioned that the
protection provided by the equipment may be impaired if the
equipment is used in a manner not specified by Ludlum
Measurements, Inc. This includes guarding against severe
impacts to the instrument housing (“can”), which could cause
damage to the internal detectors.
Section
5

MODEL 2242 Technical Manual Section5
Ludlum Measurements, Inc. Page 5-2 November 2010
The Model 2242 Survey Meter is marked with the
following symbols:
CAUTION (per ISO 3864, No. B.3.1) – designates hazardous live voltage
and risk of electric shock. During normal use, internal components are
hazardous live. This instrument must be isolated or disconnected from the
hazardous live voltage before accessing the internal components. This
symbol appears on the front panel. Note the following precautions:
Warning!
The operator is strongly cautioned to take the following
precautions to avoid contact with internal hazardous live parts
that are accessible using a tool:
1. Turn the instrument power OFF and remove the batteries
2. Allow the instrument to sit for 1 minute before accessing
internal components.
The “crossed-out wheelie bin” symbol notifies the consumer that the
product is not to be mixed with unsorted municipal waste when discarding;
each material must be separated. The symbol is placed on the battery lid. See
section 9, “Recycling” for further information.
Maintenance
Instrument maintenance consists of keeping the instrument clean and
periodically checking the batteries and the calibration. An instrument
operational check should be performed prior to each use by exposing the
detector to a known source and confirming the proper reading on each
scale.
The Model 2242 instrument may be cleaned with a damp cloth (using only
water as the wetting agent). Do not immerse instrument in any liquid.
Observe the following precautions when cleaning:
1. Turn the instrument OFF and remove the batteries.
2. Allow the instrument to sit for 1 minute before accessing
internal components.

MODEL 2242 Technical Manual Section5
Ludlum Measurements, Inc. Page 5-3 November 2010
RECALIBRATION
Recalibration should be accomplished after maintenance or adjustments
have been performed on the instrument. Recalibration is not normally
required following instrument cleaning, or battery replacement.
Note:
Ludlum Measurements, Inc. recommends recalibration at
intervals no greater than one year. Check the appropriate
regulations to determine required recalibration intervals.
Ludlum Measurements offers a full service repair and calibration
department. We not only repair and calibrate our own instruments but most
other manufacturer’s instruments. Calibration procedures are available upon
request for customers who choose to calibrate their own instruments.
BATTERIES
The batteries should be removed any time the instrument is placed into
storage. Battery leakage may cause corrosion on the battery contacts, which
must be scraped off and/or washed using a paste solution made from
baking soda and water. Use a spanner wrench to unscrew the battery contact
insulators, exposing the internal contacts and battery springs. Removal of the
handle will facilitate access to these contacts.
Note:
Never store the instrument over 30 days without removing the
batteries. Although this instrument will operate at very high
ambient temperatures, battery seal failure may occur at
temperatures as low as 37.7°C (100°F).

MODEL 2242 Technical Manual Section6
Ludlum Measurements, Inc. Page 6-1 November 2010
Setup and Calibration
Entering or Changing Switch Board
Parameters
THE FUNCTION SWITCH
A 16-position rotary switch labeled ˝0-9˝and ˝A-F˝. This switch selects a
parameter setup mode for the Model 2242. If the board is not installed,
the normal operation mode (counting mode) is selected. If the switch
board is installed, the selector switch must be set to the ˝0˝position for
normal operation. The following may be changed using this board:
•detector parameters
•RS-232 communication baud rate
•RS-232 data dump mode
•RS-232 detector parameters set/read mode
The switch board utilizes this16-position rotary switch (FUNCTION) to select
the 16 setup parameters. (Refer to schematics and component layout
drawing near the end of the manual.) All setup parameters are stored in the
non-volatile EEPROM, which will retain data even after the Model 2242
batteries are removed. After the parameters are entered, the switch board
can be removed, and the Model 2242 will operate from the programmed
information for the specific detector setup prior to the removal of the board.
oSelect the desired parameter to enter or change selecting the
corresponding FUNCTION switch position. Depress ENTER and a
character will start to flash. The flashing character indicates that the
program is in the parameter change mode.
oTo change the character, increment the UP switch to the desired
variable. To shift to another character, increment the LEFT switch,
which enables the operator to sequence through all the characters on
the LCD associated with that particular parameter.
Section
6