Basic Circuitry and X-ray Production Lynn C. Sadler, MSRS, - - PDF document

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Basic Circuitry and X-ray Production Lynn C. Sadler, MSRS, - - PDF document

Mar 19, 2023 27 likes •152 views

Basic Circuitry and X-ray Production Lynn C. Sadler, MSRS, R.T.(R)(QM) President, WCEC, Inc. X-Ray Production What are X-Rays? Where do they come from? What are some characteristics of x-radiation? How are x-rays produced?

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Basic Circuitry and X-ray Production

Lynn C. Sadler, MSRS, R.T.(R)(QM) President, WCEC, Inc.

X-Ray Production

  • What are X-Rays?
  • Where do they come from?
  • What are some characteristics of x-radiation?
  • How are x-rays produced?

From the Beginning…….

  • Why learn this “stuff”?
  • Understanding circuits and electricity makes

x-ray production more understandable.

  • Understanding x-ray production and the

characteristics of x-radiation will make you a better technologist.

– How?

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Circuit

  • The path over which an electric current

flows.

  • Consists of a source of energy, a conductor,

and a load or resistor(s) - (something that utilizes the electricity).

Circuit

  • Source of energy?

– Battery – Generator – Outlet in wall????

  • Conductor?

– Gold – Silver – Copper

Types of Circuits

  • Series

– Type of circuit where electron flow has only

  • ne path from beginning to end.
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Types of Circuits

  • Parallel

– Circuit has branches…. Electron flow has more than one path to take.

Factors in an Electric Circuit

  • Potential Difference or Electromotive Force

– Volt

  • Current

– Ampere

  • Resistance

– Ohm

Potential Difference

  • Potential Difference is the force that “drives”

electron movement in an electric circuit

– Sometimes shortened to PD – Also referred to as “emf” or electromotive force

  • The unit of potential difference is the “volt”

– Voltage is used to measure potential difference – The higher the voltage, the greater the potential difference or emf, the greater “speed” at which electrons “move” through the circuit.

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Current

  • Current is the number of electrons passing a

given point per second in an electric circuit.

– Is referred to as the “strength” or intensity of the

  • circuit. (it’s a numbers thing)
  • The unit of current is the ampere.

– The higher the amperage the more electrons that pass a given point in the circuit every second. – One ampere is equal to 6.25 x 1018 electrons flowing per second. – That’s 6,250,000,000,000,000,000 electrons

Resistance

  • Resistance is the property of an electric circuit

that hinders or opposes the flow of electrons

  • The unit of resistance is the ohm
  • The four things that determine the resistance of

a conductor are:

  • Material
  • Length
  • Cross-sectional area
  • Temperature

Factors in a cirucit

  • Potential difference, current, and resistance

are inter-related in a circuit.

  • Changing one factor will have an effect on

another factor.

  • Ohm’s Law shows that relationship between

voltage, amperage, and ohms.

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Ohm’s Law

  • Voltage = Amperage x Resistance (V = I x R)

– Remember this is a Very Important Rule

V I R

Ohm’s Law

  • If voltage is increased, and resistance is

constant, what would happen to amperage?

  • If voltage is constant, and the resistance is

increased, what would happen to amperage?

  • If voltage is constant, and the amperage is

increased, what would happen to resistance?

Ohm’s Law

  • If the total voltage is 60 volts, and the total

resistance is 20 ohms, what is the value of the current flowing through the conductor?

  • If the total resistance is 10 ohms and the

value of the current is 6 amps, what is the total voltage?

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But Wait…… There’s More!

  • One can also talk about current or a circuit in

terms of power.

  • Electrical energy, just as any other form of

energy can perform work.

– Electrical energy is convertible to a definite amount

  • f work and/or heat.

– The power of a circuit is a measure of the amount of work or heat produced. – The unit of power is the watt.

Power of a Circuit

  • P = IV or IV = P

– Power (in watts) is equal to amps x volts – Remember IVP

  • P = I2R

– Since V = I x R, one can replace the V in P = IV with I x R. That’s how we get this other formula. – Power (in watts) is equal to amps squared x resistance – Amperage produces a lot of heat. This formula is usually referred to as “power loss”

Power of a Circuit

  • Power delivered to the x-ray generator is

essentially constant.

  • One can not vary the wattage of the x-ray

circuits, but can manipulate the values of amperage and voltage and/or resistance.

  • Just remember that amps x volts has to

equal the wattage of the circuit.

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The Basic X-Ray Circuit

  • Two Circuits

– Tube Circuit

  • Provides all the wiring for the production of x-rays

– Filament Circuit

  • Provides a source of electrons so x-rays can be produced

Tube Circuit

  • Source:

– Alternating current outlet (AC) – 220 Volts – Line voltage compensator adjusts incoming voltage so that 220 volts is always delivered to tube circuit.

Tube Circuit Source

Main switch AC Source

Image from: Stewart Bushong’s Radiologic Science for Technologists

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Tube Circuit

  • Autotransformer

– Also known as the kV selector – Allows you to vary the voltage sent to the rest

  • f the tube circuit.

– Works on the principle of electromagnetic self- induction

Autotransformer

Transformer Law

Ns Vs

=

Np Vp

Image from: Stewart Bushong’s Radiologic Science for Technologists

Tube Circuit

  • Exposure timers

– Determines the amount of time the tube circuit is energized. – Five main types:

  • Mechanical - obsolete
  • Synchronous - obsolete
  • Electronic
  • mAs timers
  • Automatic exposure controls (AEC)
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Tube Circuit - Exposure Timers

Image from: Stewart Bushong’s Radiologic Science for Technologists

Tube Circuit

  • High Voltage Generator

– Is a step-up transformer – Increases voltage values to kilovoltage values – Works on the principle of electromagnetic mutual induction

Tube Circuit High Voltage Generator

Primary Side Secondary Side

Image from: Stewart Bushong’s Radiologic Science for Technologists

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Tube Circuit

  • Rectification System

– Changes alternating current (AC) to pulsating direct current (DC) – Why? ? ? ?

Image from: Stewart Bushong’s Radiologic Science for Technologists

Tube Circuit

  • X-Ray Tube

– Where x-ray production takes place.

Filament Circuit

  • Source

– Same AC outlet as for tube circuit

Image from: Stewart Bushong’s Radiologic Science for Technologists

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Filament Circuit

  • “Rheostat”

– Is a variable resistor used to regulate the filament current – Known as the mA selector – Modern tubes don’t use this anymore but utilize a high-frequency circuit to control filament current.

mA Selector in Filament Circuit

Image from: Stewart Bushong’s Radiologic Science for Technologists

Filament Circuit

  • Filament Transformer

– Is a step-down transformer – Reduces the voltage and raises the amperage in the filament circuit

Primary Secondary

Image from: Stewart Bushong’s Radiologic Science for Technologists

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Filament Circuit

  • Filament

– Current of the filament circuit passes through the filament in the x-ray tube. – High amperage of filament circuit causes the filament to become very hot. – Electrons are “boiled off” of the filament in a process called thermionic emission.

Filament of X-Ray Tube Putting It All Together!!

Image from: Stewart Bushong’s Radiologic Science for Technologists