Fluke 481 User Manual

481

Ion Chamber Survey Meter

Operators Manual

April 2011
© 2011 Fluke Corporation. All rights reserved. Specifications are subject to change without notice.
All product names are trademarks of their respective companies.

LIMITED WARRANTY AND LIMITATION OF LIABILITY

Each Fluke product is warranted to be free from defects in material and workmanship under normal use and
service. The warranty period is one year and begins on the date of shipment. Parts, product repairs, and
services are warranted for 90 days. This warranty extends only to the original buyer or end-user customer of
a Fluke authorized reseller, and does not apply to fuses, disposable batteries, or to any product which, in
Fluke's opinion, has been misused, altered, neglected, contaminated, or damaged by accident or abnormal
conditions of operation or handling. Fluke warrants that software will operate substantially in accordance
with its functional specifications for 90 days and that it has been properly recorded on non-defective media.
Fluke does not warrant that software will be error free or operate without interruption.

Fluke authorized resellers shall extend this warranty on new and unused products to end-user customers
only but have no authority to extend a greater or different warranty on behalf of Fluke. Warranty support is
available only if product is purchased through a Fluke authorized sales outlet or Buyer has paid the
applicable international price. Fluke reserves the right to invoice Buyer for importation costs of
repair/replacement parts when product purchased in one country is submitted for repair in another country.

Fluke's warranty obligation is limited, at Fluke's option, to refund of the purchase price, free of charge repair,
or replacement of a defective product which is returned to a Fluke authorized service center within the
warranty period.

To obtain warranty service, contact your nearest Fluke authorized service center to obtain return
authorization information, then send the product to that service center, with a description of the difficulty,
postage and insurance prepaid (FOB Destination). Fluke assumes no risk for damage in transit. Following
warranty repair, the product will be returned to Buyer, transportation prepaid (FOB Destination). If Fluke
determines that failure was caused by neglect, misuse, contamination, alteration, accident, or abnormal
condition of operation or handling, including overvoltage failures caused by use outside the product’s
specified rating, or normal wear and tear of mechanical components, Fluke will provide an estimate of repair
costs and obtain authorization before commencing the work. Following repair, the product will be returned to
the Buyer transportation prepaid and the Buyer will be billed for the repair and return transportation charges
(FOB Shipping Point).

THIS WARRANTY IS BUYER'S SOLE AND EXCLUSIVE REMEDY AND IS IN LIEU OF ALL OTHER
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. FLUKE SHALL NOT BE LIABLE
FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR LOSSES,
INCLUDING LOSS OF DATA, ARISING FROM ANY CAUSE OR THEORY.

Since some countries or states do not allow limitation of the term of an implied warranty, or exclusion or
limitation of incidental or consequential damages, the limitations and exclusions of this warranty may not
apply to every buyer. If any provision of this Warranty is held invalid or unenforceable by a court or other
decision-maker of competent jurisdiction, such holding will not affect the validity or enforceability of any other
provision.

Fluke Corporation
P.O. Box 9090
Everett, WA 98206-9090
U.S.A.

Fluke Europe B.V.
P.O. Box 1186
5602 BD Eindhoven
The Netherlands

11/99

To register your product online, visit

http://register.fluke.com.

Table of Contents

Title Page

Introduction........................................................................................................ 1

How to Contact Fluke ........................................................................................ 1

Features.............................................................................................................. 2

Overrange Rate.............................................................................................. 2

Low Battery Indicator.................................................................................... 2

Audio Alarm.................................................................................................. 2

Integrate Mode............................................................................................... 3

Freeze Mode .................................................................................................. 3

Auto-On Backlight ........................................................................................ 3

Specifications..................................................................................................... 3

Receiving Inspection.......................................................................................... 5

Operation ........................................................................................................... 5

External Controls........................................................................................... 5

ON/OFF Button......................................................................................... 5

Mode Button ............................................................................................. 6

Integrate Mode .......................................................................................... 6

Freeze Mode.............................................................................................. 6

Self-Test ........................................................................................................ 6

Installation ..................................................................................................... 7

Optional Check Source Use (450 UCS) ........................................................ 7

Theory of Operation........................................................................................... 7

Maintenance....................................................................................................... 9

Preventative Maintenance ............................................................................. 9

Routine Cleaning ........................................................................................... 9

Storage........................................................................................................... 10

Battery Replacement ..................................................................................... 10

Ion Chamber Window Replacement.............................................................. 10

Outer Mylar Window Replacement............................................................... 11

Desiccant Regeneration ................................................................................. 11

Lithium Cell Replacement............................................................................. 12

Replaceable Parts Information....................................................................... 13

Recalibration and Service Information.......................................................... 13

Troubleshooting Precautions ......................................................................... 13

Troubleshooting............................................................................................. 14

Self-Test Failure........................................................................................ 14

High Background Readings ...................................................................... 14

Erratic Readings........................................................................................ 14

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481

Operators Manual

ii

Introduction

The Model 481 Ion Chamber Survey Meters are hand-held, battery operated units
designed to measure beta above 100 keV and gamma and x-ray radiation above 7 keV,
using the latest CMOS and LCD technology. The 481 case is constructed of high strength
ABS plastic. A gasket and desiccant pack seal moisture out of the unit and provides a
cushion for the internal components. The readout consists of a 2 1/2-digit liquid crystal
display and a 100 segment analog bar graph. The bar graph contains a zero segment and
twenty groups of five segments each. A permanent scale is located on the display screen.
The major divisions of the scale indicate the units corresponding to the range that the
meter is measuring. Units of measurement are displayed next to the 2 ½-digit display.
LOW BAT and FREEZE will appear on the display when the instrument is operating in
these modes. External controls consist of an ON/OFF button and a MODE button. The
unit is auto-ranging and auto-zeroing. The auto-on circuit for the backlight is enabled
when twilight conditions occur. The 481 has an audio alarm that can be set by the user.
Two nine-volt batteries, located in the back of the instrument, provide over 200 hours of
continuous operation. A 440 mg/cm2 phenolic shield is provided as a beta shield. The
shield also serves as an equilibrium thickness for photon measurements & protects the
Mylar window.

How to Contact Fluke

To contact Fluke, call one of the following telephone numbers:

• Technical Support USA: 1-800-44-FLUKE (1-800-443-5853)

• Calibration/Repair USA: 1-888-99-FLUKE (1-888-993-5853)

• Canada: 1-800-36-FLUKE (1-800-363-5853)

• Europe: [phone]

• Japan: [phone]

• Singapore: [phone]

• Anywhere in the world: [phone]

Or, visit Fluke's website at www.fluke.com

To register your product, visit http://register.fluke.com

To view, print, or download the latest manual supplement, visit

http://us.fluke.com/usen/support/manuals

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481

Operators Manual

Features

The following sections describe the features of the Survey Meter.

Overrange Rate

If the instantaneous radiation rate measured by the Model 481 exceeds 50 R/h (0.5 Sv/h),
the 'R' in R/h or the 'Sv' in Sv/h displayed will blink to notify the user that the radiation
field exceeds the measuring capability of the instrument. Also, a potential error in the
integrated radiation value may exist due to this condition. The blinking will stop when
the integrated value is cleared.

Low Battery Indicator

There are about 6 hours of operation remaining when the LOW BATTERY indicator first
becomes visible. When the LOW BATTERY indicator blinks, there is less than one hour
of operation remaining. These times are for 2 batteries installed and from the first
occurrences of these indications. If the instrument is turned off during a low battery
condition, the batteries will recover somewhat, but time of operation remaining will be
less.

Audio Alarm

The audio alarm set points are set using the RS-232 COMM port connected to a computer
along with the associated software. The audio alarm set point is set in increments of 1 %
full scale. That is from 1 % to 100 % of full scale. The “A” command in the menu allows
access to the scale and percent set point. The alarm will sound when readings reach or
exceed the set point.

Figure 1. Fluke 481 Ion Chamber Survey Meter

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