Operation Manual
VacuDAP 2002
2002BA01e.DOC / 22.07.2004
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The correct installation of a printer can be verified by a test . For this purpose, the system must be set
for the MEASURE function, i.e. the POWER-ON TEST was successfully executed.
Press key
for starting the test (see 3.3.6,
PRINT function
).
2.6 Stabilization time
The ionization chamber is a highly sensitive detector. After application of the chamber voltage, it
needs some time to form and stabilize before the performance characteristics specified in the data
sheet are met. This time is called stabilization time.
Unless otherwise specified in the data sheet for the ionization chamber, a
stabilization time of 3 minutes is required.
The measuring system is ready for measurements before this time has elapsed.
2.7 Factory calibration
By means of a calibrated reference system (IEC 61674), the VacuDAP 2002 measuring system is
calibrated by the manufacturer in line with IEC 60580:2000, and meets all specifications as detailed in
the annexes.
The calibration is carried out at 70 kV, 100 mAs,
with the specified absorber
(see
Table 1: Circular
ionization chambers
) in the beam path between the measuring chamber and the patient.
Ionization chamber and detector electronics with the
same serial
number
are calibrated together by the manufacturer. A re-calibration is
necessary if ionization chamber and detector electronics with different
serial numbers are used together (see 4.4,
Checking the overall
calibration)
.
For a correct measurement of the dose area product, no additional
accessories such as absorbers or beam limiting devices may be inserted
in the beam path between the ionization chamber and the patient
In case an absorber is permanently arranged between the ionization
chamber and the patient, it needs to be taken into account in the dose
area product measurement.
The display unit has two different calibration factors (
CF_ABOVE
,
CF_UNDER
), which can be
selected by switching parameter
POSITION
to either
ABOVE
(above table, without absorber) or
UNDER
(below table, with absorber). This selection is described in Chapter 3.3.9.
Changing of
parameters.
The factory-set values for the calibration factors are shown in Table 7:
List of parameters
.
The second calibration factor,
CF_UNDER
was determined with an additional 0.5 mm aluminium
absorber for type tests (see annex:
Data sheet of ionization chamber
)
.
For regular switching between radiological examinations with and without absorber, the required
calibration factor must be selected by switching parameter
POSITION
accordingly.
By a
re-calibration
procedure authorized personnel can adjust the two calibration factors to the
prevailing installation conditions; see the instructions in Chapter 4.4,
Checking the overall calibration
.
