Ludlum Measurements 3-IS User manual

LUDLUM MODEL 3-IS AND 3-IS-1
INTRINSICALLY SAFE
SURVEY METER
October 2010
Serial Number 239605 and Succeeding
Serial Number

LUDLUM MODEL 3-IS AND 3-IS-1
INTRINSICALLY SAFE
SURVEY METER
October 2010
Serial Number 239605 and Succeeding
Serial Numbers
NOTE:
Changes to this manual require the written approval of
MET Laboratories, Baltimore, Maryland.
Warning – A special cable(Part Number 8303-764 (-xx), where xx represents
a length in feet) is supplied with the Model 3-IS. If replacement is needed, ensure
that the same type is used. This cable is identified by type “C” connectors with
locking screws and a light-blue molded-rubber strain relief. Cable lengths are
available up to 37 feet.
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]

Model 3-IS & 3-IS-1 Technical Manual
Ludlum Measurements, Inc. October, 2010

Model 3-IS & 3-IS-1 Technical Manual
Ludlum Measurements, Inc. October, 2010

Model 3-IS & 3-IS-1 Technical Manual
Ludlum Measurements, Inc. October, 2010

Model 3-IS & 3-IS-1 Technical Manual
Ludlum Measurements, Inc. October, 2010
Table of Content
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 2-3
Reading the Meter Face Dial 2-3
Operational Check 2-6
Specifications 3
Identification of Controls and Functions 4
Safety Considerations 5
Environmental Conditions for Normal Use 5-1
Connecting a Detector to the Instrument 5-1
Warning Markings and Symbols 5-2
Cleaning and Maintenance Precautions 5-3
Calibration and Maintenance 6
Calibration 6-1
Exposure Rate Calibration 6-2
CPM Calibration 6-2
Establishing an Operating Point 6-3
Maintenance 6-5
Recalibration 6-5
Batteries 6-5

Model 3-IS & 3-IS-1 Technical Manual
Ludlum Measurements, Inc. October, 2010
Troubleshooting 7
Troubleshooting Electronics which utilize a
G-M Detector or Scintillator 7-1
Troubleshooting G-M Detectors 7-3
Troubleshooting Scintillators 7-4
Technical Theory of Operation 8
Low Voltage Supply 8-1
High Voltage Supply 8-1
Detector Input 8-1
Amplifier 8-1
Discriminator 8-2
Audio 8-2
Scale Ranging 8-2
Meter Drive 8-2
Meter Reset 8-2
Fast/Slow Time Constant 8-2
Recycling 9
Parts List 10
Model 3-IS Survey Meter 10-1
Main Board, Drawing 464 × 355 10-1
Safety Board, Drawing 464 × 361 10-3
Wiring Diagram, Drawing 464 × 358 10-4
Drawings and Diagrams 11

Model 3-IS & 3-IS-1 Technical Manual Section1
Ludlum Measurements, Inc. Page 1-1 October 2010
Introduction
he Model 3-IS and 3-IS-1 are portable intrinsically safe radiation
survey instruments that are designed to be intrinsically safe in Class
1 Division 1, Group A, B, C, and D hazardous conditions. They
have four linear ranges used in combination with exposure rate,
count rate (cpm- counts per minute) or a combination of both exposure rate
and count rate (referred to as “combo”) meter face dials. The instruments
feature a regulated high-voltage power supply, unimorph speaker with audio
ON-OFF capability, fast-slow meter response, meter reset button and a six-
position switch for selecting battery check or scale multiples of ×0.1, ×1,
×10 and ×100. Each range multiplier has its own calibration potentiometer.
The unit body and meter housing are made of cast aluminum and the can is
0.090” thick aluminum.
The audio provides a brief “click” for every radiation event detected. It also
provides a steady tone to warn the user of a low battery condition. This low
battery warning overrides the position of the AUD ON-OFF switch.
There are three Geiger-Mueller (GM) detectors which are qualified for use
with the Model 3-IS. Additionally, two types of scintillation detector may be
used. The qualified GM detectors operate at 900 volts. Operating voltage
for the scintillation detectors is determined by using the plateau method
outlined on page 6-4, or by using a detector-specific procedure.
The Model 3-IS-1 features an internal energy-compensated GM detector,
and thus has no connector or cable for external detectors. This internal
detector provides for easy, one-handed operation and provides
measurement of gamma radiation up to 1000 mR/hr (1 R/hr).
The unit is operated with two ˝D˝cell batteries (Duracell Procell PC1300
1.5V Alkaline).
Section
1
T