RaySafe Xi - Manual (Page 37)

If the radiation has a pulsed characteristic, the time is measured until the last pulse ends. the dead time
interval between pulses must, however, be less than the Calc. delay time (0.5, 2, 4, 6 or 7 s). the r/f low
sensor has an electrical bandwidth of 0.1 khz (slower rising and falling slopes), causing the displayed exposure
time to be a few milliseconds longer than for the r/f high sensor, which has a bandwidth of 2.5 khz.
Figure 5. 75 % trig level activated (figure also applies to 25 and 50 % trig level settings). Please note that
the trig level setting affects the dose measurement.
single phase generators (normally dental applications) may have slowly increasing amplitude characteristics for
approximately 100 ms. It is then recommended to activate a higher trig level in the SETUP MENU after the first
exposure.
puLse
the raysafe Xi counts pulses from 1 to 9999. the trigger to increment the pulse counter occurs when the dose
rate has a negative slope and the amplitude falls below 25 % of the peak amplitude for the exposure. at peak
dose rates of approximately < 3 µGy/s (for r/f low) the signal to noise ratio is too low to count pulses and “---”
will be displayed. If possible, increase the ma and/or kVp to increase the radiation output or decrease the fdd.
pulse is available for the r/f and ma/mas detectors.
fraMe rate
the raysafe Xi calculates frame rate as: (number of pulses -1)/(exposure time in seconds). If pulses can not be
counted, the frame rate can not be calculated (see pulse section above).
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raysafe Xi user Manual – Measurement definitions