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235 Ch 5
Terms in this set (61)
For the circuit breakers are in metal electrical boxes
Main Power Switch
For exposure initiation
Two Stage Switch 1st does what...
First the rotor to speed and heats the filament
Two Stage Switch 2nd does what..
Second is for the exposure
Supplied as 60 Hz, 220-240 V
Prepares the voltage before it is transformed to kV
On/Off & Line Voltage Compensator
Single phase, full wave rectification, 2 pulse per cycle or half wave rectification 1 pulse per cycle
Single phase, Full wave rectified, 2 pulse per cycle or Half wave rectified, 1 pulse per cycle
Three phase, Full wave rectified, 6 pulse per cycle
Three phase, Full wave rectified, 12 pulse per cycle
Supplies mA to the cathode
Operators control panel
A power supply used in mobile units, in which the exposure is less accurate
In this type of mobile the NiCd supplies DC which is converted to AC.
Battery Operated Mobiles
mA falls during exposure maintaining 70-80% of loading capacity
Most efficient generation of power to the X-Ray tube, converts line voltage to 500-25,000 Hz
Contains the step-up and step-down transformers
Carry the voltage and amperage from the generator to the tube
High Tension Cables
Most common timer, accurate
Timer used in falling load and capacitor discharge to monitor mAs
mA Second Timer
Measures remnant radiation in ion chambers and terminates exposure at calibrated level
Automatic Exposure Control (AEC)
Timer in which exposure times correspond to multiples of frequency
Synchronous Motor Timer
Manual setting of maximum time for AEC exposure to run, Should be set to about 150% of anticipated mAs
On AEC, light is measured and used to terminate exposure by what?
On AEC, an ion chamber filled with xenon gas
Why is a line voltage compensator necessary, and what component serves as a line voltage compensator?
Incoming voltage fluctuates, and autotransformer
After the line voltage compensator regulates the incoming voltage, where does the voltage in the high tension circuit go?
To the step-up transformer
After the autotransformer regulates the incoming voltage,
where does the voltage in the filament circuit go
The step down transformer
If the time stations on a control console are 1/60,
1/30, 1/20, 1/15, 1/10, 1/5... what kind of timer controls it.
What would happen if the table bucky tube was
selected for an AEC chest x-ray on the upright bucky?
the exposure would be too long
What exposure factor(s) will be displayed (or are operator
controlled) when using AEC?
The kVp and mA. The time (ms) will be displayed at the end
of the exposure, for time is the device controlled variable.
The exception is that the mA would not be displayed if it were a falling load generator
What do you do when your AEC film is too light
or too dark?
Do something else, which is to override the
calabrated setting by using the AEC plus or minus
What will happen if you use a high mA station
but do not have sufficient kVp , for the size of the
patient when using the AEC?
The exposure will terminate when it hits the limit
"Transformers and-high voltage generators are usually
identified by their power rating in what?
What does a capacitor do?
Stores electrical energy for a DC discharge
What X-ray equipment are capacitor discharge
generators used for?
Mobile (portable) X-ray units
What charges the capacitor in a portable X-ray machine?
Nickel cadmium (NiCd) batteries, which are charged
by 110 V AC. They are plugged in when they are
What are modern rectifiers called?
What the purpose of a diode in the conventional x-ray circuit?
they reroute the path of
electricity to change AC to DC.
What is the purpose of a diode in high frequency generators?
they are used to change DC to AC
What classification of a conducting material are diodes?
They are semiconductors. They are also classified as solid
The earliest X-ray tubes did not have rectification. What
is the name given to the technology that describes this
Single phase, self rectified (or half wave
Give the name for each technology that followed, in
chronological order, with that of mobile X-ray units last
1. Single phase, full wave rectified
2. Three phase, six pulse (six pulse is another way of indicating full wave rectified)
3. Three phase, twelve pulse (twelve pulse is another way of indicating full wave rectification)
4. High frequency
5. Mobile X-ray units (are battery operated or capacitor
At what degree are each of the
dots (which are shown on the single phase wave) at?
0, 90, 180, 270, 360 (or back to 0)
Where do the degrees represented by dots on the single phase wave come from?
e.g., what created them?
The rotation of the armature of
How does the three phase diagram differ from the 3 phase
The three phase diagram has not yet been
rectified. The six pulse is after rectification, and is only
used this way.
What are the phase differences between a 3 phase, 6 pulse
generator, and a three phase, 12 pulse generator?
6 pulses are
120 degrees out of phase, and 12 pulses are 60 degrees out
How many pulses per second are created by each of these
Half wave = 60; Full wave = 120; Three phase, 6
pulse = 360; 3 phase, 12 pulse = 720; High frequency = up to
25,000 Hz or an average of 6000 Hz.
What is the effect of efficiency on heat units (HU)?
efficient generators create more heat units, as is expressed
buy the HU correction factor.
What is the effect on the quality and quantity of the beam?
Quality (kVp) is improved because the energy produced is
of a higher average value (the ripple)
The percentages listed are percentages of what?
The main circuit does what?
supplies the x-ray tube with properly modified power
The filament circuit does what?
supplies the filament of the x-ray tube with properly modified power
What are the two types of incoming line current?
Single and three-phase power
How many pulses per Hz are there for 3-phase power?
What device in the x-ray circuit controls the kVp?
What device in the x-ray circuit controls the mA?
What device in the x-ray circuit controls the time?
What happens to the tube mA during an exposure using a falling load generator?
Most generators will step-down the mA at 70-80 percent of the tube loading capacity.
What is the difference (location wise) between an ionization chamber and a phototimer?
Phototimers are located between the cassette and the fluorescent screen and Ionization chambers are located between the tabletop and the image receptor.
What factor determines the minimum reaction time?
The length of time necessary for the AEC to respond to the radiation and for the generator to terminate the exposure.
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