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X ray circuit
chapter 5 bushong
| Question | Answer |
|---|---|
| What are the 3 main components of the imaging system? | operating console, high voltage generator,tube |
| what is the operating console used to control? | The quality and quantity of x-ray beam |
| What type of transformers are in the high voltage generator? | a step up and a step down transformer |
| what 4 functions does the operating console allow you to control? | current (mA), voltage (kvp), exposure time, line compensation |
| why do electric circuits and meters connected to the console operate at low voltages? | to minimize possible shock hazzards |
| most x-ray imaging systems work on 220v but some can operate at _______ or ________ | 110v/440v |
| what does the line voltage compensator measure? | The voltage provided to x-ray imaging system |
| what does the line compensator adjust the voltage to? | 220v |
| what is known as the "orchestrator" in the console? | autotransformer |
| what is the auto transformer responsible for? | accepting, controlling and delivering low voltage power to the high voltage power to the high voltage/ step up transformer |
| what is usually the in put to the auto transformer? | 220v |
| what is the output of the autotransformer? | usually controllable between 100-400v |
| on an autotransformer what is the primary connections responsible for? | conducting the input power |
| what is the secondary connection of the autotransformer responsible for? | serve to either increase or decrease the voltage depending on where they are located along the winding |
| what type type of induction is the autotransformer? | self induction |
| what are taps on the autotransformer? | places where voltage exits the transformer |
| In autotransformer law what is the relation between voltage and turns ratio? | directly proportional |
| In autotransformer law what is the relation between current and voltage? | inversely proportional |
| what are the 2 kvp options on some older models? | major and minor |
| what does voltage leaving the autotransformer become? | input to the high voltage transformer |
| which side of the autotransformer is the kvp meter on? | secondary side |
| which side of the high voltage generator is the kvp meter on? | primary side |
| What is the kvp meter responsible for reading? | total voltage leaving the autotransformer before it reaches the high voltage transformer |
| What controls tube current from cathode to anode? | mA |
| The number of electrons produced through thermionic emission is determined by? | The temperature of the filament |
| what does filament current operate at? | 3-6A |
| if tube current works on 3-6 amperes what is the range in milliamperes? | 3,000-6,000 milliamperes |
| where is the filament circuit located? | along the autotransformer |
| what does the filament circuit control? | tube current |
| What is placed along the filament circuit in order to control current and create mA station? | precision resistors (or rheostats) |
| Once a mA station had been selected ,voltage travels from the mA selector switch to the_______ | filament transformer |
| Is the filament transformer a step up or step down transformer? | step down |
| what is the official name for the filament transformer? | filament heating isolation step down transformer |
| Why are the secondary windings heavily insulated on the filament transformer? | because it is connected to the high voltage supply for the x-ray tube |
| whats the difference between the primary and secondary windings on the filament transformer? | primary are thin copper and secondary thick copper |
| what is the range that the primary windings on the filament transformer carry? | .5-1A and 150 v |
| what is the range that the secondary windings on the filament transformer carry? | 5-8A and 12v |
| what does the mA meter monitor? | tube current |
| where is the mA meter? | at the center of the secondary winding of the high voltage transformer in the x-ray tube circuit |
| where are most exposure timers? | on the secondary side of voltmeter and primary side of high voltage transformer |
| what does an exposure timer control? | how long current runs through the filament |
| what is the name of a safety feature that will terminate exposure at a designated time. (~6 sec) | guard timer |
| what type of timer cannot make serial exposures because it has to be manually reset after each exposure? | synchronous timers |
| what type of timer allows for serial exposures? | electronic timers |
| what is designed to provide the highest safe tube current for the shortest time possible? | mAs timers |
| what side of the high voltage transformer is the mAs timer on? | secondary side |
| A device that measures the quantity of radiation that reaches the IR and cuts off exposure when appropriate | AEC |
| where are AEC's located? | between the patient and the IR |
| what type of timer is the AEC used in conjunction with? | electronic timer |
| back up timer should be set to _____x's the expected time | ~1.5 |
| what type of image will you get in the timer for the AEC is too short? | a light image |
| what will happen if the timer for the AED is too long? | it will add unnecessary dose to the patient and a dark image |
| what are the 2 types of AEC devices? | Ionization chambers and photomultiplier tube |
| what is in the AEC chamber of a photomultiplier tube? | a small photocathode tube |
| what are the 3 primary parts of a high voltage generator? | high voltage transformer, filament transformer and rectifiers |
| what does a high voltage generator do to output voltage from the autotransformer? | increases it to the appropriate KVp needed for x-ray production |
| what are 2 reasons the high voltage generator contains oil? | for insulation and to conduct heat from the high voltage section |
| The turns ratio is usually between ____ or ______ for a high voltage transofrmer | 500:1 /1000:1 |
| what is voltage and current measured in on the primary side of the high voltage transformer? | voltage-V current-A |
| what is voltage and current measured in on the secondary side of the high voltage transformer? | voltage-KVp current-mA |
| what type of current is required for the x-ray tube function appropriately? | direct current |
| What is the purpose of a voltage rectification? | to convert current from AC to DC |
| What are rectifiers? | electronic devices that contain diodes |
| What are diodes? | solid state electronic devices that are made of silicon or selenium and contain 2 electrons |
| what do rectifiers in a circuit determine? | how little or how much voltage is produced |
| how many diodes does half wave rectification contain? | 1 or 2 diodes |
| how many pules per second are produced by a half wave rectification? | 60 x-ray pulses per second |
| how many diodes does a full wave rectification have? | at least 4 diodes in the high voltage circuit |
| how many pulses per second are produced by a full wave rectification? | 120 x-ray pulses per second |
| what do the arrows in the diode indicate? | the direction of the current |
| what type of x-ray beam does a single phase generator produce? | pulsating x-ray beam |
| what type of generator results in 6 pulses per 1/60 sec or 360 per second? | three phase generators |
| what type of generator produces nearly constant potential voltage waveform. | high frequency generator |
| what is the voltage ripple % for 1 phase? | 100% ripple |
| what is the voltage ripple % for 3 phase and 6 pulse? | 14% ripple |
| what is the voltage ripple % for 3 phase and 12 pulse? | 4% ripple |
| what is the voltage ripple % for high frequency? | <1% ripple |
| what is the disadvantage of low ripple? | cost |
| A benefits of low ripple is ___ dose to the patient because less technique is need for the same image | less |
| What are two equations for power rating? | P=IV or W=AV |
| What is power rating expressed in? | kW |
Created by:
lchadderton
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