Fluke 35040 Operators User manual

35040
Therapy Dosimeter
Operators Manual
February 2005
Manual No. 37870 Rev. 10
©2004, 2005 Fluke Corporation, All rights reserved. Printed in U.S.A.
All product names are trademarks of their respective companies

Fluke Biomedical
Radiation Management Services
6045 Cochran Road
Cleveland, Ohio 44139
440.498.2564
120 Andrews Road
Hicksville, New York 11801
516.870.0100
www.flukebiomedical.com/rms

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Table of Contents
Section 1: General Information................................................................................... 1-1
1.1 Introduction ............................................................................................................................ 1-1
1.2 Features ................................................................................................................................. 1-1
1.3 Before you Start - Safety Precautions.................................................................................... 1-2
1.4 Safety Symbols and Terms....................................................................................................1-2
1.5 Manual Addenda.................................................................................................................... 1-3
1.6 Specifications ......................................................................................................................... 1-3
1.7 Unpacking and Inspection...................................................................................................... 1-7
Section 2: Theory Of Operation.................................................................................. 2-1
2.1 Introduction ............................................................................................................................ 2-1
2.2 Functional Description............................................................................................................ 2-1
2.2.1 Power Supply .................................................................................................................. 2-2
2.2.2 Front Panel ...................................................................................................................... 2-2
2.2.3 MicroController ................................................................................................................ 2-2
2.2.4 Serial Communications Port............................................................................................ 2-2
2.2.5 Electrometer .................................................................................................................... 2-2
2.2.6 Bias Supply...................................................................................................................... 2-3
2.2.7 Multiplexer and A/D Converter ........................................................................................ 2-3
2.3 Basic Operating Equations .................................................................................................... 2-3
2.3.1 Setting Thresholds........................................................................................................... 2-7
2.3.2 Exposure Time ................................................................................................................ 2-8
2.3.3 Air Density Correction Factor .......................................................................................... 2-9
Section 3: Operation.................................................................................................... 3-1
3.1 Setup...................................................................................................................................... 3-1
3.2 Front Panel Familiarization .................................................................................................... 3-1
3.3 Rear Panel Familiarization..................................................................................................... 3-2
3.4 Powering the System ............................................................................................................. 3-2
3.5 Power-Up Self-Test and Display Messages .......................................................................... 3-3
3.6 Ion Chamber Connector......................................................................................................... 3-3
3.7 Basic Measurement Techniques............................................................................................ 3-4
3.7.1 General Considerations................................................................................................... 3-4
3.7.2 Making Non-Timed Exposure Measurements................................................................. 3-4
3.7.3 Making Timed Exposure Measurements ............................................................3-5
3.7.4 Using Other Ion Chambers.............................................................................................. 3-6
3.8 Battery Care ........................................................................................................................... 3-6
3.9 Operation Instructions............................................................................................................ 3-7
3.9.1 Front Panel Controls........................................................................................................ 3-7
3.9.2 Powering Up the Model 35040 Therapy Dosimeter ........................................................ 3-8
3.9.3 Powering Down the Model 35040 Therapy Dosimeter.................................................... 3-9
3.9.4 Using the Test Function Button ....................................................................................... 3-9
3.9.5 Automatic Leakage Compensation ............................................................................... 3-11
3.9.6 Timer Setup ................................................................................................................... 3-13
3.9.7 Setting Thresholds......................................................................................................... 3-13
3.9.8 Using the Detector Select Button .................................................................................. 3-14
3.9.9 Using the Air Density Button.......................................................................................... 3-14
Section 3: Operation .............................................................................................. 3-1
3.9.10 Using the Units Select Button........................................................................................ 3-15
3.9.11 Using the Bias Select Button ......................................................................................... 3-15

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3.9.12 Using the Reset/Measure Button .................................................................................. 3-17
3.9.13 Overrange Conditions.................................................................................................... 3-17
3.9.14 Reset Error .................................................................................................................... 3-18
3.9.15 Reset Error (With Automatic Leakage Compensation Enabled)................................... 3-19
3.9.16 Annunciators.................................................................................................................. 3-19
3.10 Customization ...................................................................................................................... 3-21
3.10.1 Introduction.................................................................................................................... 3-21
3.10.2 Installing/Uninstalling Customization Software.............................................................. 3-21
3.10.3 Connection to the Computer.......................................................................................... 3-21
3.10.4 Starting the Customization Software ............................................................................. 3-21
3.10.5 Downloading.................................................................................................................. 3-22
3.10.6 Menu Items and Controls .............................................................................................. 3-22
3.10.7 Ion Chambers ................................................................................................................ 3-23
3.10.8 Special Items ................................................................................................................. 3-25
3.10.9 Measurement Displays .................................................................................................. 3-26
3.10.10 Timer Intervals............................................................................................................... 3-30
3.10.11 Bias Settings.................................................................................................................. 3-31
3.10.12 Examples....................................................................................................................... 3-32
3.10.13 Errors............................................................................................................................. 3-34
Section 4: Troubleshooting and Service ................................................................... 4-1
4.1 Introduction ............................................................................................................................ 4-1
4.2 Troubleshooting ..................................................................................................................... 4-1
4.3 Display Will Not Light ............................................................................................................. 4-6
4.4 Low Battery ............................................................................................................................ 4-7
4.5 Bias Error ............................................................................................................................... 4-8
4.6 Line Fuse Replacement ......................................................................................................... 4-9
4.7 Interface Connector Cleaning .............................................................................................. 4-10
4.8 Cleaning the Instrument....................................................................................................... 4-10
4.9 Replacement Parts Information ........................................................................................... 4-10
4.10 Recalibration, Repair Information & Technical Assistance.................................................. 4-11
4.11 Warranty Information............................................................................................................ 4-11
Appendix A: Sample Customization Reports................................................................A-1
A.1 Sample Documents................................................................................................................ A-1
Appendix B: Addendum Features of Firmware Version “27JAN00” or Later.............B-1
B.1 Introduction ............................................................................................................................ B-1
B.2 New Features......................................................................................................................... B-1
B.2.1 Overview.......................................................................................................................... B-1
B.2.2 Timed Measurements...................................................................................................... B-1
B.2.3 Specifications Update...................................................................................................... B-2
B.3 Setup...................................................................................................................................... B-3
B.3.1 Making Non-Timed Exposure Measurements................................................................. B-3
B.3.2 Making Timed Exposure Measurements......................................................................... B-4
B.4 Operation Instructions............................................................................................................ B-5
B.4.1 Front Panel Controls........................................................................................................ B-5
B.4.2 Using the Test Function Button ....................................................................................... B-6
B.4.3 Automatic Leakage Compensation ................................................................................. B-6
B.4.4 Timer Setup ..................................................................................................................... B-8

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Appendix B: Addendum Features of Firmware Version “27JAN00” or Later.............B-1
B.4.5 Reset Error (with Automatic Leakage Compensation Enabled)...................................... B-8
B.4.6 Annuciators, Indicators, and Overrange Conditions........................................................ B-9
B.5 Theory of Operation ............................................................................................................. B-11
B.6 Troubleshooting ................................................................................................................... B-12
B.7 Customization ...................................................................................................................... B-13
B.7.1 The Main Menu.............................................................................................................. B-13
B.7.2 The Measurement Menu ............................................................................................... B-13

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General Information
Introduction 1
1-1
Section 1
General Information
1.1 Introduction
The Model 35040 Therapy Dosimeter is designed for calibration dosimetry of therapeutic radiation
treatment machines including high-energy accelerators, 60Co, and brachytherapy equipment. The
instrument can be used for calibration, government compliance testing, installation and set-up of new
equipment, and troubleshooting.
The Model 35040 Therapy Dosimeter is a reference grade instrument that exceeds calibration
laboratories’ 1993 recommendations for linearity, long-term stability, and zero drift. The instrument uses
calibrated ion chambers to simultaneously measure and display dose and dose rate in the user specified
radiological units. At the user’s discretion, the reading may be corrected for air density by user entered
ambient temperature and barometric pressure readings.
•The highly regulated, precision electronic bias is continuously monitored. The bias voltage may be
selected from the front panel.
•The Model 35040 Therapy Dosimeter provides a timer for performing timed charge and dose
measurements. A typical application of the timer is for measuring brachytherapy sources. The
instrument supplies four timed measurement quantities, which may be added to any of the
measurement displays with the Customization software
•Triaxial ion chamber input connectors are furnished on both the front and rear of the instrument to
make it easier to set up and use.
•For the first time in a therapy dosimeter, the effective exposure time for 60Co source is determined
from a single exposure.
1.2 Features
•Low leakage current in the instrument.
•All front panel settings are stored at power down and recalled at power up.
•A wide variety of measurements are available simultaneously; including charge, dose, current, dose
rate, accumulated charge, accumulated dose, and effective exposure time.
•Timer for performing timed charge, predicted time charge and corresponding dose measurements.
•The user may select one of 32 ion chamber calibration factors for direct readout of dose or dose
rate units.
•Dose measurement values may be displayed in units of Roentgens, rads, Sieverts, or Grays. Dose
rate measurement values may be displayed in dose units per second, minute or hour. For
brachytherapy applications, the instrument may be configured to read in Curies, becquerles, or
kerma.
•The user may enter ambient temperature and pressure for air density correction of dose and dose
rate measurements. Air density correction may be turned on or off from the front panel.
•The user may select the dose rate time divisor from the front panel.

35040
Operators Manual
1-2
WARNING
•The ion chamber bias voltage may be set to one of 11 user-customized settings. The display
indicates the polarity of the central electrode and the actual measured output voltage generated by
the ion chamber bias supply.
•Highly regulated, stable, electronic ion chamber bias supply.
•The level of the internal electronic bias supply is continuously monitored. Annunciators appear on
the display if an abnormal bias voltage level is detected.
•Bright, clear, multi-line alphanumeric display.
•Simplified, uncluttered control panel.
•A wide AC line input range of 100 to 240 VAC and the use of an IEC 320/C13 style receptacle
provide worldwide operation by use of the proper line cord.
•The system may be operated from either AC line power source or from its internal battery. The
battery will be charged from AC line power during use.
•A high performance rechargeable battery system provides 8 hours of continuous operation from a
3-hour charge. A low battery annunciator indicates when 30 minutes or less of operation remains.
•Automatic power-down after a user-specified time period, when operating from battery power.
1.3 Before You Start - Safety Precautions
The Model 35040 Therapy Dosimeter should be used only by people who are:
•Aware of and understand the limitations of the device as they relate to the measurement of
radiation output
•Knowledgeable about safety procedures observed when working with radiation sources, such as
therapy radiation machines
•Aware of safety precautions required to avoid possible injury when using electrical/electronic
equipment
The Model 35040 Therapy Dosimeter is NOT
approved for applications where the sensor or the
dosimeter is in contact with the patient.
Please take the time to read this manual carefully before operating this instrument.
1.4 Safety Symbols And Terms
The following symbols and terms are found on the instrument and used in this manual.
The symbol on the instrument indicates that the user should refer to the operating instructions
located in the manual.
The symbol on the instrument shows that high voltage may be present on the terminal(s). Use
standard safety precautions to avoid personal contact with these voltages.
The heading used in this manual explains dangers that might result in personal injury or
death. Always read the associated information very carefully before performing the indicated procedure.
NOTE

General Information
Safety Symbols and Terms 1
1-3
CAUTION
The heading used in this manual explains hazards that could damage the instrument.
Such damage may invalidate the warranty.
1.5 Manual Addenda
Any improvements or changes concerning the instrument or manual will be explained in an addendum
included with the manual. Be sure to note these changes and incorporate them into the manual.
1.6 Specifications
Charge Measurements
Range, Resolution and Repeatability:
Full Scale Range Display Resolution Repeatability (±
counts)
200.00 pC 0.01 pC 5
2.0000 nC 0.0001 nC 1.5
20.000 nC 0.001 nC 2.5
200.00 nC 0.01 nC 1
2.0000 μC 0.0001 μC 1
20.000 μC 0.001 μC 1
200.00 μC 0.01 μC 1
2.0000 mC 0.0001 mC 1
20.000 mC 0.001 mC 1
Measurement Method: Charge flowing into the input is integrated using a capacitive feedback
electrometer whose output is measured by means of a 20 bit bipolar A-D converter. A high-speed reset
circuit removes the integrated charge on the feedback capacitor each time it reaches a level of 2 nC in
either polarity. By monitoring both the number of 2 nC resets and the charge on the feedback capacitor,
the total charge flowing into the input is determined.
Factory Calibration: Basic factory charge calibration is performed by injecting -1.90 nC and ±19.0 nC via
a precision standard air capacitor. This method is believed to provide a calibration accuracy of ±
0.05%rdg (± 0.05% of reading) as detailed in the table below:
Factory Calibration Error Source ± (%rdg)
Charge Source Accuracy (Capacitor) 0.01
Charge Source Accuracy (Voltage Change) 0.01
Temperature Effects (21°C – 25°C) 0.02
Other 0.01
Maximum Error 0.05
The field adjustable current and charge scale factors are set to their nominal value of 1.000 during factory
recalibration.

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Operators Manual
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Measurement Accuracy: Charge measurement accuracy is warranted to be better than ±(0.20%rdg + 2
counts) over the operating temperature range of 18°C to 28°C for 1 year.
Field Calibration: Field calibrations may be performed via a restricted distribution MS-DOS Calibration
program. This program is available to the AAPM accredited calibration laboratories (or equivalent) and
may be used to adjust the current and charge scale factors from their nominal factory setting of 1.000.
Timed Charge Measurements
Range and Resolution: Same as charge measurements.
Measurement Method: The timed charge measurement is derived by monitoring the charge integrated
over a time interval that begins with the activation of the timer. The timer automatically stops when the
elapsed time is equal to the timer interval setting or the exposure is over. Interpolation is used to
determine the charge at an integral number of seconds.
Measurement Accuracy: Same as charge measurements assuming that the rate of charge delivery does
not dramatically change within the interpolation window interval.
Current Measurements
Range, Resolution, and Noise:
Full Scale Range Display Resolution Noise
(± counts)
200.0 pA 0.1 pA 2
2.000 nA 0.001 nA 2
20.00 nA 0.01 nA 1
200.0 nA 0.1 nA 1
1.000 μA 0.001 μA 1
Measurement Method: The basic current measurement is derived by monitoring the change in the
integrated charge level over successive 1-second intervals. Dividing the change in integrated charge by
the 1-second integration period interval yields the current value.
Measurement Accuracy: Current measurement accuracy is ±(0.20%rdg + 2 counts) over the operating
temperature range of 18°C to 28°C for 1 year. Since the current measurements are based directly upon
charge measurements, an independent current calibration is not required.
Measurement Noise: Current measurement noise is typically 1 to 4 counts peak to peak (depending
upon the range) when the input is supplied by a quiet DC current source. When using a 0.6 cc Farmer
Probe to measure the output of a typical 60Co source, noise in the current measurement may be on the
order of 0.4 R/min peak to peak at 100 R/min. Normal variations in the output exposure rate produced by
a linear accelerator may result in excessive noise on the current measurement.
Response Speed: The display of current measurement values will begin within 1 second of the start of
the exposure and reach 99% of the final level within 2 seconds.
Average Current Measurements
Range and Resolution:
Full Scale Range Display Resolution
200.00 pA 0.01 pA
2.0000 nA 0.0001 nA
20.000 nA 0.001 nA
200.00 nA 0.01 nA