Test Of Mas Accuracy - Siemens MOBILETT Plus HP Maintenance Instruction

Inspection and Maintenance
2.8

Test of mAs accuracy

Requirement
The actual product of the exposure time and tube current (mAs) must match the displayed
value within the limits established by Siemens.
Required measurement devices:
Storage oscilloscope with a measurement accuracy of ± 2.5 %.
Procedure:
•
Close the collimator.
•
Connect the oscilloscope to test points "MAPOS" and "GND" on board D1.
•
Switch on the X-ray system and the oscilloscope and wait approximately 5 minutes un-
til the units have stabilized.
Example: Calculating the mAs
Fig. 22:
The mA signal is built up of a series of pulses. To get the real tube current, it is necessary
to use an oscilloscope with the possibility of showing a part of the time sweep expanded
so that each current pulse is clearly visible. Then the current can be measured according
to the figures above.
The mAs value can be calculated using the information displayed on the oscilloscope.
Surface "A" corresponds to the mAs value.
mAs
mAs
Siemens AG
Medical Solutions
= Tube current x exposure time
= 340 mA x 0.006 s
SPR8-220.101.04.03.02
07.05
= 2.0 mAs
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MOBILETT Plus HP