X-RAY CIRCUITY & Inverse Square Law
Rad Tech A - week 7
Spring 2006
DISTANCE
•Distance from the radiation source should be kept as great as possible
•Physical Law:
–Inverse Square Law
INVERSE SQAURE LAW
•Applies basic rules of geometry
•The intensity of radiation at a given distance from the point source is inversely
proportional to the square of the distance.
•Doubling the distance decreases intensity by a factor of four.
QUESTIONS ?
INVERSE SQAURE LAW FORMULA
INVERSE SQAURE LAW
•YOUR TURN 10 QUESTIONS IN CLASSX-RAY CIRCUITY
Introduction to Circuitry
Review Handouts
•Circuit Board
•Electromagnetism
Circuitry:
MAIN CIRCUIT
 Modifies incoming current to produce x-rays
Boosts voltage to range necessary produce
x-rays.
 Modifies incoming line power to produce thermionic emission from the filament wire.
FILAMENT CIRCUIT
•Filament circuit adjusts to mA ratings (50, 100, 200, etc.).
•After mA selection, current sent to step down transformer to modify amps that reach
filament on x-ray tube
3 Divisions of Circuit Board
•PRIMARY (CONTROL PANEL) yellow
•SECONDARY
(HIGH VOLTAGE) blue
•FILAMENT
(LOW CURRENT) purple
Now it is your turnName the parts of the labeled Circuit board
Important Parts
Of The Circuit Board TO ID
•1
Incoming Line Voltage
•2
Autotransformer
•3
KVP Selector
•4
Timer
•No # Ma Selector
•5
Primary Side (Low Voltage)
•6
Secondary Side (High Voltage)
•7
X-ray Tube
•8
Rectifier
•9
STEP – Up Transformer
•10
STEP – Down Transformer
AUTOTRANSFORMER
•RAISES OR LOWERS THE VOLTAGE
•KVP CONTROL TAPS LOCATED
•220 VOLTS INCOMING CONVERTED FROM 100 T0 300 VOLTS
TIMER SWITCH
•Timer switch ends exposure
•Timer – length of exposure set at control panel
How the current gets to the TUBE
Generator+ Tranformers
(where the power comes from)
TRANSFORMERS
(Step Up or Step Down)
•Increases the VOLTAGE going to the ANODE side of the tube OR
•110 volts to 110,000 volts
•Decreases the CURRENT going to the CATHODE side of the tube
•5 Amps to 50 milliamps
Current from the outlet
X-Ray Tube Circuit
Filament Current
•Current comes from Autotransformer
•Controls the Ma selection
•Focal Spot Selector Switch located here
FILAMENT CURRENT
MA METER
•MEASURE THE MA GOING TO THE XRAY TUBE
•MAINBREAKER
•EXPSOURE SWITCH
•AUTOTRANSFORMER
•TIMER CIRCUIT
•HIGH VOLTAGE STEP UP TRANSFORMER
•RECTIFIER
•FILAMENT CIRCUIT VARIABLE SELECTPR
•FILAMENT STEP DOWN TRANSFORMER
•X-RAY TUBE
•ROTOR / STATOR
EQUIPMENT REVIEW
Rotating Anode
CONTROL PANEL CONTROLS
•KVP SELECTION
(MAJOR AND MINOR)
•MA SELECTION
•TIME
Control panel