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

Model 3-IS & 3-IS-1 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-1 October 2010
Getting Started
Important:
This instrument is designed to be INTRINSICALLY SAFE in Class I
Division I Group A, B, C, and D Hazardous locations.
Warning:
Use only Duracell Procell PC1300 1.5V type “D” batteries. To reduce the
risk of ignition of a flammable or explosive atmosphere, batteries must be
changed only in a location known to be a non-hazardous area.
Warning:
When repairing this unit substitution of components may impair
INTRINSIC SAFETY.
Avertissement:
La substitution de composants peut compromettre la SECURITE
INTRINSEQUE. Afin de prevenir I’Inflammation D’Atmospheres
dangereuses, ne changer les batteries que dans des emplacements designes
non dangereux.
Section
2

Model 3-IS & 3-IS-1 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-2 October 2010
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 3-IS 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 detector(s), 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 3-IS 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 (Duracell Procell
PC1300 1.5V alkaline) in the compartment.

Model 3-IS & 3-IS-1 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-3 October 2010
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:
The center post of a “D” size battery is positive.
Connecting a Detector to the Instrument
(Model 3-IS only)
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 3-IS range selector switch to the OFF position
before connecting or disconnecting the cable or detector.
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 part number is 8303-
764(-xx), where “xx” represents a length in feet. Cable lengths are
available up to 37 feet.
Connect one end of the supplied detector cable to the detector by firmly
pushing the connectors together while twisting clockwise ¼ turn. Secure the
lock screws with an Allen wrench. Repeat the process in the same manner
with the other end of the cable and the instrument.
Battery Test
Check the batteries daily or prior to use, whichever is less frequent, to assure
proper operation of the instrument. Move the range switch to the BAT
position. Ensure that the meter needle deflects to the battery check

Model 3-IS & 3-IS-1 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-4 October 2010
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 X100
position. Place the AUD ON-OFF switch in the ON position. Expose the detector
to a check source. 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 5 times slower than the ˝F˝position.
The detector cable (on the Model 3-IS only) can be a source of problems. Test
the detector cable by bending or flexing either end of the cable and checking
for an increase in the rate of counts detected. Replace the cable if increases in
the rate of counts are detected.
Check the meter reset function by depressing the ˝RES˝ pushbutton switch and
ensuring the meter needle drops to ˝0˝.
Once this procedure has been completed, the instrument is ready for use.
Reading the Meter Face Dial
Reading the meter face is very important for consistent measurements. There
are, in general, three types of meter faces: 1) count rate (typically cpm – counts
per minute) 2) exposure rate (typically mR/hr) and 3) “combo” (typically cpm
and mR/hr.) The following examples are intended to help the user interpret
the correct reading.
The normal procedure is to turn the range selector switch to the highest range
and if no readings are seen on the meter, turn the selector switch down to the
lower scales until a reading is seen. The ranges on the instrument selector
switch are multipliers for the meter reading. A typical single scale (one arc)
meter face with a cpm (counts per minute) dial is shown on the next page.

Model 3-IS & 3-IS-1 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-5 October 2010
The count rate scale reads 0-5K COUNTS/MINUTE (kcpm or 1000’s of counts
per minute) and has BAT TEST on the dial.
If the needle is pointing as indicated below and the instrument range selection
switch is on the ×0.1 scale multiple, then the reading is 3.5 kcpm (multiplied
by) ×0.1 = 350 cpm.
The same needle indications on successive ranges would be:
×1 = 3.5 kcpm (or 3,500 cpm)
×10 = 35 kcpm (or 35,000 cpm)
×100 = 350 kcpm (or 350,000 cpm)
A typical dual scale (two arcs) meter face is shown below. The top scale reads
0-2 mR/hr. The bottom scale also reads 0-2 mR/hr and is for ×100 only scale.
The ×100 ONLY scale will work correctly when the multiplier switch is in the
×100 range. The meter face also has a BAT TEST position on the dial.

Model 3-IS & 3-IS-1 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-6 October 2010
If the needle is pointing as indicated below and the range selection switch is on
the ×0.1 scale, then the reading is 0.1mR/hr.
The same needle indications on successive ranges would be:
×1 = 1.0 mR/hr (or 1,000 µR/hr)
×10 = 10 mR/hr (or 10,000 µR/hr)
×100 = 70 mR/hr (or 70,000 µR/hr)
The dial shown below has three arcs: a counts per minute scale (cpm), a
linear mR/hr scale, and a non-linear mR/hr scale for the ×100 range only.
The meter face also has a BAT TEST position.
The top cpm scale is valid for the ×0.1, ×1, ×10 and the ×100 ranges. The
linear (middle) mR/hr scale is valid for the ×0.1, ×1, and the ×10 ranges.
The non-linear mR/hr scale is commonly referred to as a “combo” meter
face, since it has both, count rate (cpm) and exposure rate (mR/hr) arcs.
Simpler meter faces may only have a count rate or an exposure rate arc(s)
like the previous meter faces shown.
A “combo” meter face is specifically designed for a particular detector. In
the example above, the 1.0 mR/hr mark on the middle arc lines up with
3.3kcpm on the upper arc. The meter face in this example works with a
detector that receives 3.3kcpm per mR/hr (the Ludlum Model 44-9
pancake detector.) Additional detectors may be used with this meter face,
but only the cpm dial is valid for these detectors. The mR/hr scale is not
valid for these additional detectors.
In the following picture, the needle is on the first tick mark past the 4kcpm
mark. Therefore, if the instrument selector switch is on the ×0.1 range, the
reading is 4.2kcpm (multiplied by) ×0.1 = 420cpm.

Model 3-IS & 3-IS-1 Technical Manual Section2
Ludlum Measurements, Inc. Page 2-7 October 2010
The same needle indication on successive ranges would be:
×1 = 4.2kcpm (or 4,200 cpm)
×10 = 42kcpm (or 42,000 cpm)
×100 = 420kcpm (or 420,000 cpm)
If you use the mR/hr scales, then the readings would be:
×0.1 = 0.13 mR/hr
×1 = 1.3 mR/hr
×10 = 13 mR/hr
×100 = 180 mR/hr*
Note:
*This reading is using the bottom (non-linear) scale.
Many different dials are available, but each can be used as described above.
Operational Check
To assure operation of the instrument and detector(s) between calibrations, an
instrument operational check including battery test and instrument test (as
described above) should be performed at least daily or prior to use, whichever
is less frequent. A reference reading (or readings) with a check source should
be obtained with the detector(s) in a constant and reproducible manner at the
time of calibration or at the time the instrument is received in the field.
If at any time the instrument fails to read within 20% of the reference reading
when using the same check source, it should be sent to a calibration facility for
recalibration and/or repair. If desired, multiple readings may be taken at
different distances and/or with different sources so that other ranges or scales
are checked.

Model 3-IS & 3-IS-1 Technical Manual Section3
Ludlum Measurements, Inc. Page 3-1 October 2010
Specifications
Power: two ˝D˝cell batteries (Duracell Procell PC1300 1.5V alkaline)
housed in a sealed externally accessible compartment.
Battery Life: typically greater than 2000 hours with the AUD ON-OFF switch
in the OFF position.
End-of-Battery Life Warning: At 2.1 Vdc the meter needle will drop to the
edge of the BAT TEST or BAT OK area when the meter selector switch is
moved to the BAT position. At 2.0 Vdc a steady audible tone will be emitted
to warn the user of the low battery condition.
High Voltage: adjustable from 400 to 1100 volts.
Threshold: fixed at 40 mV ±10 mV.
Meter: 6.4 cm (2.5 inch) arc, 1 mA analog type.
Meter Face: Typically 0-2 mR/hr, or 0-5k cpm + BAT TEST (others
available). (Model 3IS-1 is 0-10 mR/hr. BAT TEST)
Range: typically 0-200 mR/hr, or 0-500,000 counts/minute (cpm).(M3IS-1
is 0.1 mR/hr to 1.0 R/hr)
Linearity: reading within 10% of true value with detector connected.
Battery Dependence: less than 3% change in readings to battery failure
indication.
Audio: built-in unimorph speaker with ON-OFF switch (greater than 60 dB
at 2 feet).
Response Time: toggle switch for fast (4 seconds) or slow (22 seconds)
from 10% to 90% of the final reading.
Connector (Model 3-IS only): series ˝C˝
Size: 16.5 x 8.9 x 21.6 cm (6.5 x 3.5 x 8.5 inch) (H x W x L)
Section
3

Model 3-IS & 3-IS-1 Technical Manual Section3
Ludlum Measurements, Inc. Page 3-2 October 2010
Weight: 1.6 kg (3.5 lb) including batteries.
Construction: cast and drawn aluminum with beige powder-coat
Environmental Rating: NEMA 3R –constructed for either indoor or
outdoor use to provide a degree of protection against falling dirt, rain, sleet,
and snow.
Cable (Model 3-IS only): a special 39 inch coaxial cable with set-screw-
locking ˝C˝connector and light blue molded rubber strain relief is provided
with each instrument.
Warning (Model 3-IS only): A special cable is supplied (Part Number
8303-764(-xx), where “ xx” represents a length in feet)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.

Model 3-IS & 3-IS-1 Technical Manual Section4
Ludlum Measurements, Inc. Page 4-1 October 2010
Identification of Controls and
Functions
See the Model 3-IS FRONT PANEL drawing at the
beginning of this manual to reference the following
controls:
Meter: 2.5" (6.4cm) arc, 1 mA analog type with pivot-and-jewel suspension.
Typical meter dials are 0-2 mR/hr, 0-20 µSv/h, 0-5k cpm or combination of
exposure rates (0-2 mR/hr or 0-20 µSv/h) and cpm and BAT TEST.
Connector: (Model 3-IS only) Series “C”, used to connect the detector to the
instrument.
Range Selector Switch: A six-position switch marked OFF, BAT, ×100, ×10,
×1, and × 0.1. Turning the range selector switch from OFF to BAT provides
the operator with a battery check of the instrument. A BAT check scale on the
meter provides a visual means of checking the battery-charge status. Moving
the range selector switch to one of the range multiplier positions (×100, ×10,
×1, and × 0.1) provides the operator with an overall range of 0 to 500,000
cpm. Multiply the scale reading by the multiplier to determine the actual scale
reading.
Calibration Controls: Recessed potentiometers which are used to calibrate
the individual range selections and allow for high voltage adjustment from
400 to 1100 volts. A protective cover is provided to prevent tampering.
Battery Compartment: Sealed compartment to house two ˝D˝cell batteries.
RESET Button: When depressed, this switch provides a rapid means to drive
the meter to zero.
AUD ON-OFF Switch: In the ON position, operates the unimorph speaker,
located on the left side of the instrument. The frequency of the clicks is
relative to the rate of the incoming pulses. The higher the rate,
Section
4