KaVo In eXam 3510, Инструкции техника

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Technician's instructions KaVo In eXam 3510
1 Product description
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1.2 Functioning of In eXam electronics
▪ Switching to 4 mA causes the relay to be energised, and the resistor is again
series-connected >> R > I . LD 5 shines.
1.2.3 Exposure
▪ The trigger in the control unit is activated
▪ In the 1st stage,
– The "Heating Control" signal is emitted by the control unit, and the corre‐
sponding relay is energised. Subsequently, the charging capacitors for cur‐
rent limiter are connected to the mains voltage via a series resistor and the
rectifier, and charged. The voltage supply is therefore available for the power
output stage.
– At the same time, the unisolated vo5VDC and +15VDC are applied
at the preamplifier, and LD 1 shines.
– Cathode heating is activated, LD 4 (Vheat) and LD 6 (Fil heat) shine
▪ In the delayed second stage,
– the signal "X ray control" is output by the control unit. Subsequently, the
corresponding relay is operated, whereby the charging resister of the capa‐
citor bank is bridged, and the capacitors are directly supplied from the mains.
– The kV control (described below) is activated, and high voltage is subse‐
quently applied to the tube.
– LD 8 "Cmd KV" shines during the display
1.2.4 Vheat control
The tube current is indirectly regulated by means of the heat voltage.
▪ The reference voltage V
heatref
is applied to the comparator. This depends on the
different components such as tube voltage (60/70 kV) and tube current (4/7 mA).
▪ Depending on this reference voltage, the heating voltage V
heat
is applied to the
filament of the tube.
▪ The heating voltage is simultaneously applied as a feedback signal to the com‐
parator, and compared to the reference voltage V
heatref
. If V
heat
deviates, the
voltage is adjusted and thereby kept constant.
▪ If the heating voltage cannot be adjusted corresponding to the instructions, ex‐
posure is terminated, and in the error message "power error" is output by the
control unit.
1.2.5 kV selection and kV control
▪ The kV is selected with the control unit. By means of the signal CMD kV, a re‐
ference voltage at the comparator is applied to this setting.
▪ The kV controller generates a square wave signal with an f0 that depends on
the preselected kV.
▪ The square wave signal is amplified by the preamplifier and power output stage.
▪ By means of the arm cable, this voltage is transferred to the transformer in the
x-ray head and transformed upward. The higher or lower f0 that is output cor‐
responding to the preselected kV has an effect here. The higher the frequency
of the voltage at the primary winding, the lower the induced voltage at the se‐
condary winding, i.e., the frequency f0 has higher with the selected 60kV than
with the preselected 70kV.
▪ Subsequently, this voltage is quadrupled via an 8-level cascade, and then it is
applied to the anode. Given the relatively higher frequency (~ 300kHz), the low
capacitance of the high-voltage cascade is sufficient to smooth the alternating
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