44 Inspection and maintenance
MOBILETT Plus/ -E/ -M SPR8-215.831.04.03.02 Siemens AG
07.05 CS PS 24
Page 44 of 64
Medical Solutions
2.8 Test of mAs accuracy
Requirement
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 comprised of a series of pulses. To get the real tube current, it is neces-
sary to use an oscilloscope with the possibility of showing part of the time sweep
expanded so that each current pulse is clearly visible. The current can then 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.
The actual product of the exposure time and tube current (mAs) must match the dis-
played value within the limits established by Siemens.
mAs = Tube current x exposure time
mAs = 340 mA x 0.006 s = 2.0 mAs
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