Chapter A - GENERAL & TECHNICAL DATA
Planmeca Proline CC panoramic x-ray A-7
Technical Manual
Starting exposure
If the pre-heat phase was passed without error the high voltage generator is enabled. In normal
conditions the kilovolts will rise within about 8 ms and the mA-value rises simultaneously.
Depending on the component tolerances the voltage rise will start from 5 to 15 ms after the ena-
ble first was active. After 40 ms from the enabling both the tube voltage and current are moni-
tored. If the voltage has not reached the desired value within 6 kV the generator will be stopped
with an error indication ‘kilovolts do not rise’. Correspondingly, if the current is not within 1 mA the
generator is stopped with indication ‘mA does not rise’.
Generator current limit
The high voltage generator has a current limit circuit built in the hybrid IC10. It will limit the cur-
rent of the end stage to about 13 A cycle by cycle basis. The normal operating current at maxi-
mum exposure parameters is about 7.5 A but when the generator is started the charging of the
cascade capacitors need some extra current. In the case that the tube head is short circuiting
momentarily or continuously this circuit will limit the current through the end stage FET’s Q6 -
Q10 to about 13 A. The microprocessor monitors the tube head parameters after 40 ms from the
beginning of an exposure and during the exposure with a time interval of 2.5 ms. If the end stage
was operating at full 13 A current the FET’s would be overheated within few seconds but the
microprocessor detects the problem and stops the generator well before anything will break
down.
Exposure parameter check
During the exposure the microprocessor monitors all the parameters and adjusts them. If for
some reason the kV-value drops more than 6 kV from the nominal, the exposure is stopped with
error indication ‘kV does not rise’. Also, if the mA-value differs more than 1 mA from the nominal
the exposure is stopped with an error indication ‘mA does not rise’ or ‘filament control inopera-
tive’ when overcurrent is detected.
Tube arching
If during the exposure a sudden drop of kV is detected the generator is stopped with an error indi-
cation ‘Sudden drop of kV detected’. If the x-ray tube is arching this is normally the procedure.
However, it might happen that the kV drops down and rises back up between the 2.5 ms micro-
processor measurement interval. In this case the generator is stopped by overvoltage and error
indication “overvoltage in tube head” will be displayed.
Overvoltage detection
The generator has a separate overvoltage detection circuitry that will stop the generator if the
tube head voltage exceeds about 92 kV. The microprocessor is monitoring and adjusting the volt-
age, but this circuit is a separate hardware comparator, working independently from the micro-
processor.
Generator time out
The longest panoramic exposure takes a little above 18 seconds. The microprocessor has an
independent timer routine to check the exposure time. If it exceeds 22 seconds the generator is
stopped with time out error indication. In service mode this timer will stop exposure without error
indication if the exposure switch is continuously pressed. To be able to operate the equipment’s
two microprocessors must have their clock frequencies synchronized to each other better than
1%. This guarantees that the timer function will be accurate enough.
Summary of Contents for Proline CC
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Page 186: ...Chapter H PARTS REPLACEMENT REPAIR H 8 Planmeca Proline CC panoramic x ray Technical Manual...
Page 202: ...Chapter I FUNCTIONAL DESCRIPTION I 16 Planmeca Proline CC panoramic x ray Technical Manual...
Page 203: ...Planmeca Proline CC panoramic x ray J 1 Chapter Technical Manual J SCHEMATICS DIAGRAMS...
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