44
X-ray tube checks
MAMMOMAT Novation DR
SPB7-250.815.06.02.02
Siemens AG
12.05
CS SD 24
Page 44 of 116
Medical Solutions
7-
6X-ray tube checks
Tube high voltage, current and mAs values
0
This section describes how to check the X-ray tube in regard to the:
•
High voltage, tube current, mAs value with and without AEC and with a small or large fo-
cus.
Preparation
0
•
Switch the system
OFF
.
•
Connect the oscilloscope as follows:
Channel 1 to measuring point
HV_ACT
(actual value)
(1 V= 5 kV) on the D750.
Channel 2 to measuring point
MA_ACT
(actual value)
(1 V= 40 mA) on the D750.
•
Connect the service PC to the stand.
•
Switch the system
ON
.
•
Start the Service Program and check in the
anode menu
whether the tungsten anode
is
enabled
.
Measurement method
0
•
The mAs value must be calculated as the product of the tube current and exposure
time. The tube current and the exposure time can be obtained from the oscillograms.
The diagram may have glitches, in which case you have to measure the exposure time
t1 and t2.
Example:
Fig. 27: Check x_ray tube high voltage _ current and mAs values
From the figure, the tube current is 150mA and the exposure time is t
1
+t
2
in seconds. The
mAs is 150mA*(t
1
+t
2
)
NOTE
Be aware that with the AEC mode on, a pre-exposure of 50 ms is
done.
Select the correct trigger on the scope so you get the pre-exposure
and all the exposure times.