SIB2316 Sensor Interface Board SensL SPMArray2
- 14 -
Vertilon Corporation, 66 Tadmuck Road, Westford, MA 01886
/
Tel: (978) 692-7070
/
Fax: (978) 692-7010
/
www.vertilon.com
Zero Slope Discriminator
Timing extraction from the charge pulse is accomplished by means of a zero slope discriminator whose timing is shown in
Figure 6. Using the preamplifier output as its input, the discriminator works by generating a positive-going digital timing
signal (ZSD) at the inflection point of the charge pulse input. It is at this point where the pulse is at its peak and its slope
transitions from positive to negative. The internal signal DIFF is effectively the derivative of the input pulse and therefore
crosses zero when the slope of its input is zero. This point is the trigger point in the figure. The actual digital timing output
from the discriminator goes high after a small delay (t
d
) relative to the trigger point. To minimize the effects of noise and
other particle events not of interest, a comparator in the discriminator compares DIFF to a user-adjustable energy
threshold (V
th
) so that only events exceeding the threshold result in a signal on ZSD — all other events are ignored. The
energy threshold adjustment to the SIB2316 is provided through the SIB cable so that the user can vary the threshold
using the SIB2316 dialog box in the PhotoniQ graphical user interface. The zero slope discriminators have four bandwidth
settings which along with the discriminator gain can similarly be adjusted through the GUI. For certain applications the
discriminator type can be switched to leading edge discrimination instead of zero slope discrimination.
Figure 6: Zero Slope Discriminator Timing
V
th
TRIGGER
POINT
ENERGY
THRESHOLD
POINT
ZSD
DIFF
COMMON
ANODE
CURRENT
PREAMP
OUTPUT
t
d
Summary of Contents for SIB2316
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