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Section D
3.3.
kV ACCURACY
The peak tube potential is defined as the average peak value of the
high voltage (except single spurious peaks).
The kV setting on the operator panel determines the absolute
maximum kV value during the exposure.
In some projections, the kV are automatically adjusted during the
exposure to compensate the variation in the object thickness (see
table below): in these cases only the part of the exposure where
the kVp is at the maximum value must be considered for the
measurement.
P
R
O
J
E
C
T
O I
N
S
T
A
N
D
A
R
D
P
A
N
O
R
A
M
C I
C
H
L I
D
D
E
N
T
T I
O I
N
O
N
L
Y
R
G I
H
T
J
A
W
L
E
F
T
J
A
W
The kV range is 60-84 kV, with steps of 2 kV.
The high voltage accuracy is ± 3 kV.
The measuring method is by the feedback circuit of the converter
board.
The measurement procedure is the following:
(1)
Inhibit the movements during the exposure.
(2)
For the measurement connect a multimeter to test points TP
13 (kV feedback signal) and TP 20 (GND) of Converter board
PQ1.
(3)
Select V - DC on the multimeter.
(4)
Start the exposure selecting standard projection. After the
stabilization time (about 2 sec.), record the voltage readout
on the multimeter and stop the exposure.
(5)
Check that the high voltage conforms to the specification.
The relation between kV and feedback signal on TP 13 is indicated
in the table below:
N
O
M
N I
A
L
V
A
L
U
E
k (
k
V
F
E
E
D
B
A
C
K
T
P
3 1
0 6
6
0 .
2 6
6
2 .
4 6
6
4 .
6 6
6
6 .
8 6
6
8 .
0 7
7
0 .
2 7
7
2 .
4 7
7
4 .
6 7
7
6 .
8 7
7
8 .
0 8
8
0 .
2 8
8
2 .
4 8
8
4 .
D-2
M
A
X
k
V
M
O
D
U
L
A
T
O I
R
E
S
P
E
C
T
T
O
T
H
S
E
L
E
C
T
E
D
V
A
L
U
-
6
%
-
7
%
-
8
%
-
0 1
%
-
0 1
%
) V
A
C
C
E
P
T
A
N
C
E
R
A
N
G
. 5
0 7
. 6
0 3
. 5
0 9
. 6
0 5
. 6
0 1
. 6
0 7
. 6
0 3
. 6
0 9
. 6
0 5
. 7
0 1
. 6
0 7
. 7
0 3
. 6
0 9
. 7
0 5
. 7
0 1
. 7
0 7
. 7
0 3
. 7
0 9
. 7
0 5
. 8
0 1
. 7
0 7
. 8
0 3
. 7
0 9
. 8
0 5
. 8
0 1
. 8
0 7
3.4.
TIMER ACCURACY
The exposure time is defined as the time during which the envelope
of the X-ray producing mA is over 25% of its maximum and steady
value.
The exposure time accuracy is ± 0.020 second or ± 1%, whichever
is the greater.
To measure exposure time, a timer counter can be used connected
at the mA feedback TP 16 on the converter board PQ1.
Alternatively, a radiation monitor can be used; in this case the basic
N
accuracy for exposure time measurement of the radiation monitor
E
must be considered.
E
Measure the following exposure times:
M
P
A
N
(
T
P
A
N
(
S
C
C
C
C
E
P
H
(
C
E
P
H
(
Inhibit the movements during the exposures.
Check that the results conform to the specification.
3.5.
RADIATION DOSE RATE
Measure the radiation dose at a distance of 20 cm from the focus.
Inhibit movements during the exposures.
Dismount the collimator and place the dosimeter at 20 cm. from the
focus.
E
(
) V
Using the parameters listed in the table below, make three exposures
and multiply the value read on the dosimeter by 60 to have the dose
rate in R/min.
k
V
6
0
7
0
8
0
Check that the results conform to the specification, with a tolerance
of ± 30%.
(03.0)E
ORTHORALIX 9200
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DENTSPLY Gendex
Service Manual
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