LUDLUM 9-3 User manual

LUDLUM MODEL 9-3
ION CHAMBER
June 2018
Serial Number 261657 and Succeeding
Serial Numbers

LUDLUM MODEL 9-3
ION CHAMBER
June 2018
Serial Number 261657 and Succeeding
Serial Numbers

MODEL9-3 TechnicalManual
i

MODEL9-3 TechnicalManual
ii
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]

MODEL9-3 TechnicalManual
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Table of Contents
Introduction 1
Getting Started 2
Battery Installation 2-1
Battery Test 2-1
Instrument Test 2-2
Operational Check 2-3
Specifications 3
Identification of Controls and Functions 4
Safety Considerations and Maintenance 5
Environmental Conditions for Normal Use 5-1
Warning Markings and Symbols 5-1
Metallized Polyester (Mylar) Window Precaution 5-2
Cleaning and Maintenance Precautions 5-2
Maintenance 5-3
Recalibration 5-3
Batteries 5-3
Desiccant 5-3
Return for Repair and Calibration 5-4
Technical Theory of Operation 6
Chamber 6-1
Chamber Window 6-1
Electrometer 6-1
Range Change 6-2
Reset 6-2
Offset Adjustment 6-2
Zero Adjust 6-2

MODEL9-3 TechnicalManual
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Range Calibration 6-3
Range Changing 6-3
Power Supplies 6-3
Audio Circuit 6-4
Meter Circuit 6-4
Recycling 7
Parts List 8
Model 9-3 Ion Chamber 8-1
Main Circuit Board, Drawing 293 × 680 8-1
Electrometer Board, Drawing 293 × 670 8-4
Wiring Diagram, Drawing 293 x 525 8-5
Drawings and Diagrams 9

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Ludlum Measurements, Inc. Page 1-1 June 2018
Introduction
he Ludlum Model 9-3 is a five-range ion chamber instrument for
measuring beta-gamma radiation up to 50 R/hr. The chamber wall,
including the instrument case, is 1000 mg/cm². A 1000 mg/cm²
retractable beta shield allows beta measurement with a 7 mg/cm²
window.
The six-position selector switch selects OFF, ×10K, ×1K, ×100, ×10, and
×1. Each range has a front-panel mounted calibration control. Other
features include an audio pulsing in proportion to the meter reading,
RESET, and ZERO ADJUST. An additional calibration control “L” is
utilized to zero electrometer offset voltage.
The unit is powered by two “AA” cell batteries for operation from -20 to 50
°C (-4 to 122 °F).
Section
1
T

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Ludlum Measurements, Inc. Page 2-1 June 2018
Getting Started
Battery Installation
Ensure the Model 9-3 range selector switch is in the OFF position. Open the
battery lid by pushing down and turning the quarter-turn thumbscrew
counterclockwise one quarter of a turn. Install two “AA” size batteries in the
compartment.
Note the (+) and (-) marks inside the battery holder. Match the battery polarity
to these marks. Insert the negative end of the battery firmly against the spring
in the battery holder, then push the positive end of the battery forward to
ensure contact is made at both ends of the battery. Close the battery box lid,
then push down and turn the quarter-turn thumb screw clockwise one quarter
of a turn.
Note:
The center post of a battery is positive. The batteries are placed in
the battery compartment in opposite directions.
Battery Test
The batteries should be checked each time the instrument is turned on. This is
accomplished simply by pressing the BAT TEST button. Ensure that the meter
needle deflects to the battery test portion of the meter scale. If the meter does
not respond, check to see if the batteries have been correctly installed. Replace
the batteries if necessary.
Section
2

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Ludlum Measurements, Inc. Page 2-2 June 2018
Instrument Test
Note:
The Model 9-3 has two options for chamber wall voltage. An
internal jumper may be selected to allow continuous voltage on
the chamber wall with the instrument turned off. This option
allows a faster, three-minute settling time when the instrument is
frequently used. If the instrument is infrequently used, it is
recommended that this option not be used, because of battery
drain. Battery life with the continuous wall voltage on and
instrument off is approximately six months.
Without this option, the battery drain is zero with the instrument
OFF. When the instrument is turned on, a settling time of 5
minutes is required for a reading of less than 0.2 mR/hr, 10
minutes for less than 0.1 mR/hr, and several hours for readings
near zero.
The instrument will be shipped with the chamber wall voltage
turned on when the instrument is turned off.
After checking the batteries with the range switch on the ×10K position, turn
the instrument range switch to the ×1 position. Note that as the selector switch
moves from ×100 to ×10, a meter transient will occur. This transient is caused
by an internal range relay and is normal. Allow time for the ×1 scale to stabilize.
Open the beta shield slide. Switch the AUD ON OFF switch to ON. Expose
the chamber window to a check source. Observe that the audio click frequency
increases as the meter reading increases.
Note:
The RESET circuit discharges the chamber and opens the
chamber connection to the electrometer. This causes a transient
on the ×1 and ×10 scales. The meter will indicate full scale and
count-down for five seconds when the RESET switch is pressed
and released. For near zero reading on ×1 scale, allow several
more seconds for setting time after RESET is released.

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Ludlum Measurements, Inc. Page 2-3 June 2018
Open the beta shield and expose the check source to the center of the chamber
window. The instrument reading should be within 20% of the check source
reference after settling time.
Note:
The depressions on the side of the instrument housing indicate the center
of the chamber.
Once this procedure has been completed, the instrument is ready for use. When
using the instrument, open the beta shield for greater beta response, and close
for less.
Caution!
Damage to the metalized polyester window on the back side of the
instrument may result when the slide is open if careful instrument
handling is not practiced. The window is very fragile and may be
punctured quite easily.
Operational Check
To assure proper operation of the instrument between calibrations and periods
of non-use, an instrument operational check, including battery test and
instrument test (as described above), should be performed prior to use. A
reference reading with a check source should be obtained at the time of initial
calibration, or as soon as possible, for use in confirming proper instrument
operation. In each case, ensure a proper reading on each scale. If the instrument
fails to read within 20% of a proper reading, it should be sent to a calibration
facility for recalibration.