46 Inspection and maintenance
MOBILETT Plus/ -E/ -M SPR8-215.831.04.03.02 Siemens AG
07.05 CS PS 24
Page 46 of 64
Medical Solutions
2.9 Check for reproducibility
Requirement:
NOTE
The following test requires 10 sequential exposures, which must
be taken within one hour.
After each measurement, the exposure parameters should be set
to different values for a short time.
If the MOBILETT is equipped with a DAP measuring system, re-
move the DAP ionization chamber first.
Required measurement devices:
• Dose meter
Procedure:
• Wait until the system has reached thermal stability. A 15 minute warm-up time is re-
quired for the generator to be ready.
X
• Release the specified number of exposures with the following exposure data:
- 85 kV, 1.0 mAs, 10 exposures.
• Measure the dose for each exposure with the dose meter.
• Reset the measurement display prior to each new measurement.
Calculations: Fluctuation coefficient C
• The fluctuation coefficient C for a dose measurement sequence of 10 exposures is:
Fig. 23:
Where:
The fluctuation coefficient C must be ≤ 0.045.
Setting
• The coefficient of fluctuation of the radiation dose may not be greater than 0.045 for
any combination of exposure parameters if the X-ray system is supplied with line volt-
age as specified by Siemens.
s = standard deviation of the measurements
= average measurement value of the sequence
x
i
= i-th measurement value of the sequence
n = number of measurements in the measurement sequence
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