NOMEX
Operating Manual - Error Messages and Erroneous Measurements
D909.131.00/02 en
75
11.2 Erroneous Measurements
Problem
Cause
Remedy
The measured tube voltage
was higher than expected.
When performing measurements
on systems, excessive tube volt-
ages may occur at the begin-
ning of the exposure. Since the
NOMEX multimeter measures the
peak voltage, this peak value will
be indicated.
Using the start delay adjustment of the
Measurement
menu, these start-up over-
shoots can be excluded. The NOMEX
multimeter will start saving the tube volt-
age values only after the start delay has
elapsed.
The actual total filtration is dif-
ferent from the setting on the
NOMEX multimeter.
Compare the NOMEX multimeter filter
setting with the filtration on the X-ray unit
and correct it if necessary.
An X-ray tube's roughness may increase
with age and utilization. This leads to
additional filtration that must be taken
into account when setting the total filtra-
tion at the NOMEX multimeter.
The NOMEX multimeter is capable of
automatically determining the total filtra-
tion. This eliminates the need for manual
adjustments.
NOTE
:
The parameter set on the NOMEX multi-
meter is total filtration, not the half value
layer.
The wrong calculation is being
analyzed. For example, a peak
voltage is compared with a PPV
calculation.
Using three different computation meth-
ods, the NOMEX multimeter determines
three kV results: kVp
max
, kVp
mean
and
PPV.
(After a measurement, you can read
them on the measuring window by
repeatedly clicking the measured quan-
tity.)
The measured tube voltage
was higher or smaller than
expected.
Compared with the start delay,
the exposure time is too short. A
falling edge is being analyzed.
Reduce the start delay or set it to zero
to allow the entire exposure time to be
analyzed.
