Fluke Biomedical 8000 Victoreen - Manual (Page 27)

2
Operation
Modes of Operation
2-15
When a negative measurement delay is specified, the NERO mAx does not include the delay time in the
measured exposure time. A negative measurement delay should be used in cases when x-ray generator
filament preheat pulses or other waveform anomalies should be excluded from kV and exposure time
measurements. In the example shown below, a 10-pulse exposure is preceded by 14 filament preheat
pulses. Using a -230 millisecond delay to skip over the filament preheat pulses results in a measured
exposure time of 10 pulses.
Negative Measurement Delay
0%
20%
40%
60%
80%
100%
120%
0 50 100 150 200 250 300 350 400
msec
Rel
a
ti
ve Radi
ati
o
n
A negative delay is used to skip over
filament preheat pulses
Exposure time measured
with a negative delay
An example showing this use of a measurement delay can also be found in troubleshooting Section 4.8--
Waveforms - Dental With Filament Preheat.
When the measurement delay is positive, the NERO mAx includes the delay time in its measured
exposure time. A positive measurement delay should be used in cases when the kV waveform contains
leading edge overshoot or other waveform anomalies that should be excluded from kV measurements but
included in the exposure time measurement. In the example shown below, an overshoot occurs in the
first few milliseconds of a 50-millisecond exposure. Using a +10 millisecond delay to skip the overshoot
results in a measured kVp of 72 versus 82 and an exposure time of approximately 50 milliseconds.