3. Description of the QABrowser
Real-time Display and Waveforms
Piranha & QABrowser Reference Manual
2014-06/5.5C
46
on the Real-Time Display, see Indicators and Symbols .
AMX-4
The difficulties when measuring tube voltage on a GE AMX-4 is a well-known problem.
Due to high kV ripple at a frequency of 2 kHz it is hard for most non-invasive kVp-
meters to follow the kV waveform correctly.
This waveform type has an agreement with measurements made with the Keithley Triad
System 37946C mobile filter pack (50-135 kV), which is the only filter package
recommended by GE. According to GE, the use of the standard Keithley 37617C W-R
filter pack (50-150 kV) is not good enough. The results have further been verified with
measurements with a traceable high voltage divider that has sufficient bandwidth to
accurately follow the kV ripple from the AMX-4.
Therefore it is important to select the AMX-4 waveform
under Settings | Conditions.
More about the AMX-4 correction can be found in the
Application Note 1-AN-52020-1 from RTI Electronics
AB.
Pulsed
This waveform type should be used for pulsed fluoroscopy especially when the pulses
do not have a "good" square waveform shape. The exposure time must be longer than
the selected recording time when using this waveform type. Pulsed waveform type is
selected under Settings | Conditions in the same way as the AMX-4 waveform type.
Conditions - Pulse rate
Conditions - Pulse rate
If a pulsed mode is used, like pulsed fluoroscopy or
pulsed radiography (cine) the pulse rate can be
specified in pulses per second (same as Hz). This
allows you to get a dose/pulse reading even if the
detector used (e.g. ion chamber) is too slow for the
Piranha electrometer to detect the pulses. A solid-state
detector, like the Piranha Dose Probe, is however fast
enough to detect the frequency even for very low-level
signals.
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