Ludlum Measurements 18 User manual

LUDLUM MODEL 18
ANALYZER
March 2012
Serial Number 217996 and Succeeding
Serial Numbers

LUDLUM MODEL 18
ANALYZER
March 2012
Serial Number 217996 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. March 2012
Table of Contents
Introduction 1
Getting Started 2
Unpacking and Repacking 2-1
Battery Installation 2-1
Connecting a Detector to the Instrument 2-2
Battery Test 2-2
Instrument Test 2-2
Operational Check 2-3
Specifications 3
Identification of Controls and Functions 4
Safety Considerations 5
Environmental Conditions for Normal Use 5-1
Warning Markings and Symbols 5-1
Cleaning and Maintenance Precautions 5-2
Calibration and Maintenance 6
Establishing an Operating Point 6-1
Calibration 6-1
GM Detectors 6-2
Proportional Detectors 6-2
Scintillation Detectors 6-3
Window Calibration 6-3
HV Calibration 6-4
Ratemeter Calibration 6-5
Detector Overload (Option) Calibration 6-5
With Scintillation Detectors 6-5
With GM Detectors 6-5
Maintenance 6-6
Recalibration 6-7

Model 18 Analyzer Technical Manual
Ludlum Measurements, Inc. March 2012
Batteries 6-7
Troubleshooting 7
Troubleshooting Electronics which utilize a
GM, Scintillator, or Proportional Detector 7-1
Troubleshooting GM Detectors 7-3
Troubleshooting Scintillators 7-4
Troubleshooting Proportional Detectors 7-4
Recycling 8
Parts List 9
Model 18 Analyzer 9-1
Main Board, Drawing 363 × 509 9-1
Calibration Board, Drawing 363 × 513 9-3
Wiring Diagram, Drawing 363 × 515 9-4
Drawings and Diagrams 10

Model 18 Analyzer Technical Manual Section1
Ludlum Measurements, Inc. Page 1-1 March 2012
Introduction
he Ludlum Model 18 Analyzer supplies the complete electronic
requirements for scintillation, proportional or GM monitoring with
the added feature of a window amplifier for selective gamma
monitoring.
The analyzer has three high-voltage potentiometers with a three-position
selector switch to choose the high-voltage operating point. Each high-
voltage potentiometer may be preset for a specific energy or detector. Other
features include AUD ON/OFF and fast/slow (F/S) meter response switches,
meter RESET, and high-voltage (HV) test buttons. The instrument includes a
unimorph speaker and is complete with connector cable and batteries.
Three gamma thresholds may be detected by utilizing the three preset high-
voltage settings. For example, the gamma threshold can be set for above 10
keV, above 30 keV, and above 100 keV. In the presence of mixed radiation,
including plutonium, americium and uranium 235, a quantitative estimate of
the source contribution of each isotope can be made by measuring each
energy level.
The Model 18 also incorporates a window circuit allowing a narrow peak to
be monitored. For example, by setting the window at 1.5 times threshold,
settings of 12 keV through 18 keV for plutonium, 45 keV through 67 keV
for americium, and 130 keV through 195 keV for 235 U may be used for a
better estimate.
Section
1
T

Model 18 Analyzer Technical Manual Section 2
Ludlum Measurements, Inc. Page 2-1 March 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 18 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 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
Battery Installation
Ensure the Model 18 range selector switch is in the OFF position. Open the
battery lid by pushing down and turning the quarter-turn thumbscrew
Section
2

Model 18 Analyzer Technical Manual Section 2
Ludlum Measurements, Inc. Page 2-2 March 2012
counter-clockwise a quarter 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, push down, and turn the
quarter-turn thumb screw clockwise a quarter 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 18 range selector switch 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 a quarter of a turn. Repeat the
process in the same manner with the other end of the cable and the
instrument.
BatteryTest
The batteries should be checked each time the instrument is turned on.
Move the range switch to the BAT position. Ensure that the meter needle
deflects to the battery check portion on the meter scale. If the meter does
not respond, check to see if the batteries have been correctly installed.
Replace the batteries if necessary.
Instrument Test
After checking the batteries, turn the instrument range switch to the ×1000
position. Place the AUD ON-OFF switch in the ON position and the WIN
IN/OUT switch to the OUT position. Expose the detector to a check source.

Model 18 Analyzer Technical Manual Section 2
Ludlum Measurements, Inc. Page 2-3 March 2012
The instrument speaker should emit ˝clicks˝ relative to the rate of counts
detected. The AUD ON/OFF switch will silence the audible clicks if in the OFF
position. It is recommended that the AUD ON/OFF switch be kept in the OFF
position when not needed in order to preserve battery life.
Rotate the range switch through the lower scales until a meter reading is
indicated. While observing the meter fluctuations, select between the fast
and slow response time (˝F/S˝) positions to observe variations in the display.
The ˝S˝position should respond approximately five times slower than the
˝F˝position.
Note:
The slow response position is normally used when the
instrument is displaying low numbers, which require a more
stable meter movement. The fast response position is used at
high rate levels.
Check the meter reset function by depressing the RES pushbutton and
ensuring the meter needle drops to ˝0.˝When the RES pushbutton is released
the meter needle recovers to the original reading.
Depress the HV pushbutton and note that the meter indicates the high-
voltage set point.
Note:
HV power supply has an output impedance of 10 megohms.
HV load should not exceed 25 microamperes. Calculate the
scintillation detector loading if an exact high voltage setting is
required.
See calibration procedures for details on the WIN IN/OUT operation.
Once this procedure has been completed, the instrument is ready for use.
Operational Check
To assure proper operation of the instrument between calibrations and
periods of nonuse, an instrument operational check including battery test
and instrument test (as described above) should be performed prior to use.