Fluke 90100 manual Theory of Operation

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Theory of Operation

Introduction 3

Section 3

Theory of Operation

3.1 Introduction

The Model 90100 TRACKER System is a radiation measurement system intended for use in quality assurance programs for high-energy accelerators and Co60. The two main components of the system are the Model 35300A Detector and the Model 35360A TRACKER Display. This section describes the basic theory of operation of these devices. For more information regarding radiation dosimetry and ion chamber measurement theory, the reader should refer to one of the standard radiology physics texts.

The section begins with a simplified hardware block diagram of the Model 35360A Display accompanied by a short description of the most important blocks. Next follows a short description of the Model 35300A Detector and a discussion of air density corrections. The section concludes with a description of the system's basic operating parameters and equations.

3.2Overall Functional Description of the Model 35360A TRACKER Display

The 35360A TRACKER Display contains a five-channel electrometer capable of producing measurements of dose and dose rate. Its 4 line by 20 character vacuum fluorescent display (VFD) can display the measurement results directly in the user's choice of radiological units. These readings may include air density corrections if desired. An integrated rechargeable battery and a 300 V electronic bias supply greatly simplify maintenance of the system. The 35360A TRACKER Display includes an RS-232 serial communication port that allows complete computer control of the measurement system. This communications port, in conjunction with internal non-volatile memory, also provides a means of customization and calibration of the 35360A TRACKER Display.

Figure 3-1 is a simplified hardware function block diagram for the 35360A TRACKER Display. While the most important interblock connections have been shown, many interconnections have been omitted in order to maintain clarity. Three external connections are illustrated. These are the AC Line, the RS-232 Computer Interface, and the Detector Input.

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Contents Tracker System ModelFluke Biomedical Table of Contents Appendix a Using Build-Up Maintenance and ServiceTheory of Operation CustomizationIntroduction General InformationModel FeaturesSafety Terms Before You Start Safety PrecautionsSpecifications Manual AddendaMechanical Specifications Nominal Ion Chamber CharacteristicsRecommended Operation Conditions Ion Chamber Factory CalibrationDisplay Mode Measurements ModeModel 35360A Tracker Display Electrometer / A-D ConverterUnpacking and Inspection High Performance Battery ChargerInterface Cable Detector to Display EnvironmentOptional Equipment Standard System ContentsBlank Rear Panel Familiarization OperationDetector Input Powering the SystemDisplay. Be sure to use the correct end of the cable 3 RS-232 Computer Interface RJ-45 Style Positioning the Model 35300A Detector in the BeamOperation Positioning the Model 353300A Detector in the Beam Front Panel Controls Operation InstructionsReset PowerTest/Detector Units SelectUsing the TEST/DETECTOR Button Powering Up the Model 35360A Tracker DisplayPowering Down the Model 35360A Tracker Display Test/Detector Screen 2 Ion Chamber Calibration Factors Using the Units Select ButtonUsing the Gain Select Button Normal Mode Using the AIR Density ButtonAbsolute Measurements Using the Measure Select Button Normal ModePercent-of-Center Measurements Underranging and Overranging Conditions Battery and Bias Annunciators24. Positions of the Battery and Bias Annunciators Gain Setting ModeAborting the Fpgf Changes Saving the Fpgf ChangesBlank Theory of Operation Hardware Block Diagram of the Model 35360A Tracker Display Power Supply2 300-VOLT Electronic Bias Supply Front Panel SwitchesProcessor VFD DisplayMultiplexer and A/D Converter Serial Communications PortElectrometer Air Density Corrections Model 35300A Ion Chamber DetectorsBasic Operating Equations Basic Operating Quantities Blank Maintenance & Service Problem TroubleshootingNo Display Flowchart Low battery Yes Annuciator displayed? Low Battery Indication at the Display35360A Tracker Bias Error LoBias or HiBias Indication at the DisplayLeakage Flowchart Dose Rate Measurement Zero Problem Flowchart Line Fuse ReplacementIf fuses continue to blow return instrument for repair Replaceable Parts Information Interface Connector CleaningCleaning the Instrument Recalibration & Repair Information / Technical Assistance Replaceable Parts ListCustomization Connection to the Computer Make a Working DiskStarting the Customization Software Screen FormatsDisplay Customization Items Screen Appearance F2 Edit Item Editing F1 Help On-Line Help for using the Customization softwareF6 Print Report Printing F10 ExitDefinitions Charge Gain QG Setting the Electrometer Gains and OffsetsCurrent Gain, Current Zero IG and ADZ Ion Chamber Calibration Factor IccfElectrometer Charge Gains QG Electrometer Current Gain IGUsage Examples Changing the Power Down IntervalChanging the ION Chamber Calibration Factor Units Input Errors ErrorsBuild-Up, Peg, and Retainer Kit Options Using Build-UpNominal Number of build-up Solid Water Appendix Fluke Biomedical