Chapter F - PREVENTIVE MAINTENANCE
Planmeca Proline EC X-ray unit F-5
PREVENTIVE MAINTENANCE CHECKS
Technical Manual
Exposure time measurement
The exposure time is controlled by the microprocessor, so the exposure time accuracy is
exactly the same, no matter if the set exposure time is 200 ms (in film-based cephalostatic
mode) or 16 s (in panoramic / tomographic mode). The exposure time is defined automatically
based on the selected program and is displayed in the upper right corner of the graphical user
interface. In panoramic mode, attach the non-invasive sensor to the front panel of the cas
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sette holder (or Dimax3 sensor) and make sure its whole area is in the radiation field. Select
70 kV / 8mA and press ready. Take an exposure and record the measured exposure time.
The measured exposure time must be within ±10% of the exposure time displayed in the user
interface.
In film-based cephalostatic mode, the exposure time is selected by the user. Select the short-
est possible exposure time, attach the non-invasive sensor to the cephalostatic cassette
holder in the middle of the radiation field, take an exposure and record the measured expo
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sure time. When placing the sensor, note that if the unit is equipped with auto-ceph, the cas-
sette size is automatically detected when the cassette is on its place and the area of radiation
field is adjusted accordingly.
2.2.2 INVASIVE TESTING (directly from the units own feedback signals)
NOTE The manufacturer does not require the invasive testing. The invasive test must only be
performed if the local authorities require it.
An invasive method should be used for checking the tube current (mA), and can be used for
checking the kVp and exposure time. This method requires that the covers around the tube
head assembly are removed. The analog feedback voltage signals can be measured with a
calibrated multimeter. An oscilloscope is required if kV and mA waveforms need to be
observed, for an example when determining the exposure time.
Peak tube potential (kVp) measurement
Select the voltage mode of the multimeter. Connect the positive plug of the multimeter to the
Generator CPU board’s connector P18:10 KVM-signal. Connect the negative plug of the mul
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timeter to the Generator CPU board’s connector P4:2 (GND). Select the appropriate DC volt-
age measurement range for 1 to 5 V signal level. Take an exposure with desired kV setting
(selected mA value has no effect, however low mA should be used to minimise the amount of
unnecessary radiation) and when the voltage reading has stabilized, record it. The actual tube
voltage relates to the measured feedback signal as follows:
Actual tube voltage = 17 467 * measured feedback voltage (in volts)
The resulting tube voltage should be within ±5% of the voltage indicated in the user interface.
Tube current (mA) measurement
Select the voltage mode of the multimeter. Connect the positive plug of the multimeter to the
Generator CPU board’s connector P18:11 MAM-signal. Connect the negative plug of the mul
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timeter to the Generator CPU board’s connector P4:2 (GND). Select the appropriate DC volt-
age measurement range for 100mV to 5 V signal levels. Take an exposure with desired mA
setting (selected kV value has no effect, but lowest possible kV is recommended to minimise
the amount of unnecessary radiation) and when the voltage reading has stabilized, record it.
The actual tube current relates to the measured feedback signal as follows:
Actual tube current (in mA) = 2.61 * measured feedback voltage (in volts)
The resulting tube current should be within ±10% of the current indicated in the user interface.
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