Instruction Manual
DIAMENTOR E
- 10 -
Adjusting the DIAMENTOR E
[D151.131.0/3]
6
Adjusting the DIAMENTOR E
6.1
Adjustment during the Installation
The DIAMENTOR E is calibrated in the factory. During this calibration the ionization chamber
gets a chamber factor KG. The DIAMENTOR E itself gets a characteristic factor QT. The
product of these two factors gives the check reading nc:
nc = QT
⋅
KG.
(1)
This check reading nc must be adjusted by using the calibration potentiometer (see picture 3,
5).
The procedure should be performed as follows:
Connect the chamber to the DIAMENTOR E. Press the test button for approximately 1 s, then
release it and read the value on the display. If this displayed value differs from the calculated
nc, the calibration potentiometer must be adjusted. Repeat this procedure until the correct value
of nc is displayed. The RESET button must be pressed before each test.
6.2
Checking the Calibration after Installation
During the factory calibration the chamber factor kG is measured with an absorber of 0.35 mm
Al equivalent between the ionization chamber and the X-ray focus. This absorber simulates a
mean value between undercouch and overcouch X-ray tube installations.
If the DIAMENTOR E is used on an overcouch tube (with no additional absorption between
chamber and patient), the factory calibration causes a reading that is approximately 9 % too
low. When the ionization chamber is used on an undercouch X-ray tube (where there is
approxi-mately 0.5 mm - 0.7 mm Al equivalent between chamber and patient), the reading of
the DIAMENTOR E is approximately 3 % too high.
A precise check of the calibration after installation is only possible by comparison with a
reference dosemeter. This check should be done annually.