Ludlum Measurements 2224-1 User manual

LUDLUM MODEL 2224-1
SCALER / RATEMETER
January 2012
Serial Number 125559 and Succeeding
Serial Numbers

LUDLUM MODEL 2224-1
SCALER / RATEMETER
January 2012
Serial Number 125559 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 2012
Table of Contents
Introduction 1
Getting Started 2
Unpacking and Repacking 2-1
Internal Switches 2-1
Battery Installation 2-2
Connecting a Detector to the Instrument 2-2
Battery Test 2-2
Operating the Instrument 2-3
Principle of Operation 2-3
Specifications 3
Description of Controls and Functions 4
Operator Controls 4-1
Internal Controls 4-2
Safety Considerations 5
Environmental Conditions for Normal Use 5-1
Cleaning Instructions and Precautions 5-1
Warning Markings and Symbols 5-2
Calibration and Maintenance 6
Calibration 6-1
Establishing an Operating Point 6-1
Meter Calibration 6-2
Detector Overload Calibration 6-4
Maintenance 6-5
Recalibration 6-5
Batteries 6-5
Technical Principle of Operation 7

MODEL 2224-1 Technical Manual
Ludlum Measurements, Inc. January 2012
Troubleshooting 8
Recycling 9
Parts List 10
Model 2224-1 Scaler / Ratemeter 10-1
Amplifier / Power Supply Board, Drawing 390 × 104 10-1
Processor Board, Drawing 390 × 107 10-4
Calibration Board, Drawing 390 × 112 10-4
Display Board, Drawing 390 × 127 10-5
Interconnect Board, Drawing 390 × 124 10-5
Wiring Diagram, Drawing 390 × 110 10-5
Drawings and Diagrams 11

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Ludlum Measurements, Inc. Page 1-1 January 2012
Introduction
he Model 2224-1 is a portable microprocessor based radiation
survey instrument used to measure and discriminate low-level
alpha/beta radiation when used with an alpha/beta scintillation or
proportional detector.
The data is displayed by an analog ratemeter and a six-digit liquid crystal
display (LCD) counter. The ratemeter dial indicates 0-500 CPM with four
linear range multipliers of ×1, ×10, ×100, and ×1000, producing an overall
range of 0-500 kCPM. The LCD is used to display the counts accumulated
during the preset count time. Four count times are available for selection
through a front-panel switch. These count times are: 0.5, 1, 2 and, 5 minutes.
The counter is reset and started by pressing the count button located in the
end of the carrying handle.
The ratemeter and LCD can display alpha only, beta only, or alpha and beta
by selecting the corresponding toggle switch selection. Audible click-per-
event tones can also be selected to discriminate beta (low pitch tone) from
alpha (high pitch tone) via the side-mounted speaker. Beta threshold,
window, and alpha threshold are adjustable to optimize alpha/beta efficiency
and count separation.
A regulated high-voltage power supply adjustable from 400 to 2000 volts
with detector overload detection is utilized to operate a wide range of
scintillation detectors. Other operating features of the instrument include
programmable audio divide-by (beta channel only), a two-position switch
(internal) for selecting the audio discrimination mode, audio headphone jack,
adjustable volume, battery test pushbutton, high-voltage display pushbutton,
and a ratemeter reset pushbutton.
The unit body is made of cast aluminum with a drawn aluminum can. The
unit is operated with two ˝D˝cell flashlight batteries for operation from -10
oC to approximately 50 oC (14 to 122 °F). For operation to -10 oC (14 °F),
either very fresh alkaline or rechargeable NiCd batteries may be used.
Section
1
T

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Ludlum Measurements, Inc. Page 2-1 January 2012
Getting Started
Unpacking and Repacking
Remove the calibration certificate and place it in a secure location. Remove
the instrument 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 2224-1
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 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. 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
Internal Switches
Release the can latches and remove the cover from the instrument, taking
care not to damage the speaker wires. Using a ball-point pen, set the
Section
2

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Ludlum Measurements, Inc. Page 2-2 January 2012
switches for the desired AUDIO division and TONE as described on Page 4-3.
Replace the cover and fasten the latches.
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 one-fourth of a 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, then push down and turn
the quarter-turn thumb screw clockwise one-fourth of a turn.
Note:
The center post of a flashlight battery is positive. The batteries
are placed in the battery compartment in opposite directions.
Connecting a Detector to the Instrument
Caution!
The detector operating voltage (HV) is supplied to the detector
via the detector input connector. A mild electric shock may
occur if you make contact with the center pin of the input
connector. Switch the Model 2224-1 to the ˝OFF˝position
before connecting or disconnecting the cable or detector.
Connect one end of a detector cable to the detector by firmly pushing the
connectors together while twisting clockwise one-fourth of a turn. Repeat
the process in the same manner with the other end of the cable and the
instrument.
Battery Test
The batteries should be checked each time the instrument is turned on.
Move the range selector switch to the BAT position. Verify that the overload
(OL) LED on the front panel turns on briefly. The LCD should go through
an initialization sequence displaying ˝88:8.8:8.8,˝then the current sample
number, and finally ˝0.˝Ensure that the meter needle deflects to the battery
check portion on the meter scale. If the meter does not respond, check to

MODEL 2224-1 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-3 January 2012
see if the batteries have been correctly installed. Replace the batteries if
necessary.
Operating the Instrument
Connect a detector to the instrument if you have not already done so.
Obtain a meter reading from a check source or calibrated source, if available.
Verify that the reading falls within the expected range. Remove the source.
If a radiation source is available, increase the meter count to exceed the
counting capability of the instrument, signified by the illumination of OL
LED and full-scale needle deflection.
Depress the RESET pushbutton. The meter needle should drive to zero, and
the alarm circuit should de-energize, shutting off the visual alarm.
Select the desire count channel display (α/α+β/β) and count cycle duration
(MIN) and proceed with use.
Principle of Operation
The Model 2224-1 is to be used in combination with alpha/beta scintillation
or proportional detectors. The instrument uses pulse heights discrimination
to distinguish between alpha and beta pulses from the radiation detector.
The detected alpha count is displayed by selecting the αposition on the
three-position α, α+ β, and βtoggle switch. The sum of the alpha and beta
counts are displayed in the α+ βposition, and beta counts are displayed in
the βposition. Multiply the CPM reading on the analog ratemeter by the
range multiplier position. When using the LCD and count cycle selector
switch (MIN), the counts are accumulated in each of the three channels
during the count cycle. The alpha, alpha + beta, and beta counts can be
displayed by selecting the appropriate α, α + β, β channel. The count cycle is
started by depressing the pushbutton switch located in the end of the
carrying handle.
The RESET pushbutton switch resets the meter pointer to zero. The detector
operating voltage is displayed on the meter dial, 0-2 kV (kilovolts), by
depressing the HV switch. The OL (overload) lamp, located in the lower
right-hand corner of the meter dial, is to indicate that the detector is
saturated either by a puncture in the detector face on a scintillation detector
or an exposure to a radiation field above the counting capability of the
instrument. The analog meter will deflect full-scale when the OL lamp is
illuminated.

MODEL 2224-1 Technical Manual Section3
Ludlum Measurements, Inc. Page 3-1 January 2012
Specifications
0
Ranges: four linear range multiples of ×1, ×10, ×100 and ×1000; used in
combination with the 0-500 CPM meter dial, providing an overall range of
0-500 kcpm
Thresholds: beta threshold (BT) is adjustable from -2 to -10 millivolts
(mV); alpha threshold (AT) is adjustable from -50 to -150 mV
Window (beta only): Beta window (BW) is adjustable from 20-40 mV
Audio: dual or single-tone click-per-event (beta only) through a built-in
speaker with an adjustable volume control located on front panel; headset
jack located on the instrument ˝can˝
High Voltage: externally adjustable from 400 to 2000 Vdc
Linearity: within 10% of true value for the analog rate meter; within 2%
for the LCD
Crosstalk: no more than 10% of gross alpha counts in beta channel; no
more than 1% of gross beta counts in alpha channel
Response Time: ×1 range multiplier = 10 seconds, ×10 = 7 seconds,
×100 = 2 seconds, ×1000 = 1.5 seconds; all response times measured
from 10-90% of full scale
Meter: rugged 1 milliamp (mA), with pivot-and-jewel suspension, 8.3 cm
scale, 250 degree
LCD: six-digit direct-driven with 6.4 mm characters, a counter overflow
arrow and colons for indicating a count in process
Connector: Standard series ˝C,˝others available
Section
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Ludlum Measurements, Inc. Page 3-2 January 2012
Power: two standard ˝D˝cell batteries
Battery Dependence: instrument calibration change less than 3% to
battery endpoint
Battery Life: exceeds 350 hours with a fresh set of alkaline ˝D˝cell
batteries
Temperature Range: -20 to 50 °C (-4 to 122 °F)
Finish: drawn-and-cast aluminum, with beige powder coating
Size: 16.5 x 8.9 x 21.6 cm (6.5 x 3.5 x 8.5 in.) (H x W x L)
Weight: 1.6 kg (3.5 lb), including batteries

MODEL 2224-1 Technical Manual Section4
Ludlum Measurements, Inc. Page 4-1 January 2012
Description of Controls and
Functions
Operator Controls
OFF/BAT/X1000/X100/X10/X1 Switch (or Range Selector Switch): a six-
position rotary switch to select the analog meter range multipliers and
check the battery status. When switched to the BAT position, the meter
pointer should deflect above the left vertical mark on the BAT OK or BAT
TEST line. Moving the range selector switch to one of the range multiplier
positions (×1, ×10, ×100, ×1000) provides the operator with an overall
range of 0-500 kcpm. Multiply the scale reading by the multiplier to
determining the actual reading.
During the initial turn-on, the meter is driven full-scale for about two
seconds and then returns to zero. The LCD will then show “888888,”
display the processor program version, and then “0.”
Liquid Crystal Display (LCD): six-digit display that shows the scaler count
for the selected channel. The display also indicates when a count is in
progress by displaying two colons. The colons are turned off when the
count is completed. If the counter exceeds 999999, an arrow in the upper
left corner of the display turns on to indicate the overflow, and the
counter rolls over to zero and continues counting.
VOL: Turning this control clockwise will increase the speaker volume, and
counterclockwise will decrease the volume.
Note:
The volume should be turned down, when not required, to
reduce battery drain.
α / α+β / β Switch: a three-position toggle switch used to select the sum
of both alpha and beta count channels (α+β), alpha count only (α), or
beta count only (β) for display. This switch affects both the ratemeter
and the counter. The separate ratemeter and counter channels are active
Section
4

MODEL 2224-1 Technical Manual Section4
Ludlum Measurements, Inc. Page 4-2 January 2012
regardless of the switch position and will continue to function when the
channel is not selected for display. This allows the operator to view each
channel separately or together by simply selecting the appropriate switch
position.
Headphone Jack: 1/8 inch headphone jack for connection of external
headphones. Connecting the headphones results in the disconnection of
the external unimorph speaker from the audio circuitry. Use 1/8 inch
mating plug (LMI part # 21-9653).
RESET/HV: a dual-position momentary toggle switch, which provides
readout of the detector high voltage when the HV position is selected and
provides a rapid means of driving the analog meter to zero when the RES
position is selected. Use the 0-2 kV meter scale for high-voltage readings.
Count Pushbutton (located in the carrying handle): When depressed, the
counter is reset to zero, and the timer is started. Colons on the display
indicate a count cycle is in progress.
Remove the CAL cover to access the following:
HV Adjustment: provides a means to vary the high voltage from 400 to
2000 volts.
Internal Controls
Remove the instrument cover (can) to access
the following dipswitches on S301:
Dipswitch1 & 2 (Audio-divide select): a two-pole DIP switch used to
select the audio divide ratios of 1, 10, 100, and 1000.
Note:
The AUDIO divide function only affects the lower frequency
beta tones. The higher frequency alpha clicks per events will be
unaffected by the divide-by selection.

MODEL 2224-1 Technical Manual Section4
Ludlum Measurements, Inc. Page 4-3 January 2012
The ratio is selected from the following table. (O is open and C is closed)
SWITCH DIVIDE BY
1 2 RATIO
C C 1
O C 10
C O 100
O O 1000
Dipswitch 3 & 4 (SPARE):Not used
Dipswitch 5 (TONE): a one-pole DIP switch used to select tone
discrimination between alpha and beta count channels. When in DUAL
mode (Cposition), alpha and beta pulse tones will be audible in all
selector switch positions (i.e. if in the αonly position and βis detected,
the βtones will be heard in addition to the αtones and visa versa).
When the SNGL tone position (Oposition) is selected, both alpha and beta
pulse tones can be heard in the α+βselection, but alpha pulses cannot be
heard in the beta only channel selection and beta pulse tones will not be
heard in the alpha only channel selection.
Dipswitch 6 (SPARE): Not used
The following controls are utilized during
calibration only and should only be adjusted by a
qualified calibrator.
MTR: a multi-turn potentiometer used to calibrate the meter to the CPM
reading.
AT: a multi-turn potentiometer used to vary the alpha pulse threshold
from approximately -40 to -700 mV.
BW: a multi-turn potentiometer used to vary the beta pulse upper
window limit from the beta threshold to the alpha threshold setting and
anywhere in between those two parameters. The beta window can be
disabled by adjusting the BW control to the maximum clockwise position,
allowing the upper beta threshold limit to equal the alpha threshold.
BT: a multi-turn potentiometer used to vary the beta pulse threshold
from approximately -2 to -15 millivolts.

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OL: a multi-turn potentiometer that provides a means to vary the detector
current overload set point.
LIM: a multi-turn potentiometer used to set the maximum HV limit to
2000 Vdc.
HV: a multi-turn potentiometer used to adjust the high-voltage test
reading to correspond with the actual high-voltage output. HV must be
selected on the RES/HV toggle switch during adjustment.
LB:a multi-turn potentiometer used to adjust the minimum battery
voltage level, corresponding to the low-battery indication on the meter
dial. The range selector switch must be in the BAT position during
adjustment.

MODEL 2224-1 Technical Manual Section 5
Ludlum Measurements, Inc. Page 5-1 January 2012
Safety Considerations
Environmental Conditions for Normal Use
Indoor use only
No maximum altitude
Temperature range of -20 to 50 °C (-4 to 122 °F)
Maximum relative humidity of less then 95% (non-condensing)
Pollution Degree 3 (as defined by IEC 664) (Occurs when conductive
pollution or dry nonconductive pollution becomes conductive due to
condensation. This is typical of industrial or construction sites.)
Cleaning Instructions and Precautions
The Model 2224-1 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 one minute before cleaning.
Section
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Ludlum Measurements, Inc. Page 5-2 January 2012
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.
The Model 2224-1 Scaler / Ratemeter 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 one minute before accessing
internal components.
CAUTION, RISK OF ELECTRIC SHOCK (per ISO 3864, No. B.3.6)
– designates a terminal (connector) that allows connection to a voltage
exceeding 1 kV. Contact with the subject connector while the instrument is
on or shortly after turning off may result in electric shock. This symbol
appears on the front panel.
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. This symbol is placed on the battery lid. See
section 9, “Recycling,” for further information.
The “CE” mark is used to identify this instrument as being acceptable for
use within the European Union. This symbol is located on the battery lid.

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Calibration and Maintenance
Calibration
Note:
Local procedures may supersede the following.
ESTABLISHING AN OPERATING POINT
The detector operating parameters are established by adjusting the detector
operating voltage (HV), alpha threshold, and beta window to find an
optimum efficiency for the alpha/beta scintillator or proportional detector.
The threshold and window parameters can be adjusted to optimize
alpha/beta count discrimination, count efficiency, and minimize "cross talk"
between channels. Refer to the specific detector Operation Manual or
calibration certificate for the suggested threshold and window settings.
Once the thresholds and window settings are established, an operating
voltage versus count rate plot should be performed for both alpha and beta
count channels with alpha and beta particle emission sources.
The following procedure is an example of determining the operating voltage
for an alpha/beta scintillation or proportional detector:
1. Connect a Ludlum Model 500 Pulser or equivalent to the
Model 2224-1.
2. Switch the Model 2224-1 channel selector to the β position.
Adjust the beta threshold (BT) for 3.5 mV and the window
(BW) for 30 mV. The pulser counts should be detected on
the Model 2224-1 ratemeter above 3.5 ±1 mV and should
shut off above 30 mV.
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3. Switch the channel selector switch to the α position. Adjust
the pulser for a 120 mV pulse output and vary the AT
control until counts are detected on the ratemeter.
4. Depress the HV switch and adjust the HV potentiometer for
0.4 to 0.5 kV on the 0-2.0 kV scale. Connect the scintillator
and switch to the β only position. Place an alpha source on
the detector face.
5. Slowly increase the HV potentiometer to observe an
increase, then decrease, and increase again in count as the
HV is increased. Decrease the HV until the ratemeter is in the
"dip" of the observed count rate versus HV plot just
performed. Depress the HV switch and note the HV setting.
6. Plot a HV versus count rate plateau in 25-volt increments, 50
volts each side of the HV reading found in the above step
(ie, HV setting for count "dip" in the above step = 675 volts,
start the plot at 625 volts and increase in 25-volt steps until
725 volts is reached). Plot alpha source, beta source, and
background counts for both the α and β channel positions.
7. Find the optimum operating voltage from the plot, which
gives the greatest alpha and beta source efficiency while
maintaining no greater than the maximum acceptable level
of "cross talk" between channels.
8. Select the desired count channel display, and proceed with
use.
METER CALIBRATION
A Ludlum Model 500 Pulser or equivalent is required. If the pulser does not
have a high-voltage readout, use a high-impedance voltmeter with at least
1000 Megohm input resistance to measure the detector voltage.
1. Ensure that the meter movement has proper mechanical
zero. The adjustment is on the front of the meter bezel. It
must be adjusted to zero with the range selector switch in
the OFF position.
2. Connect the Model 500 Pulser to the Model 2224-1 with the
appropriate cable. Rotate the Model 2224-1 range selector
switch to the ×100 position. Select the α+β channel
position.