5.
Pole/Zero Value
The four-digit value, located under the pole/zero slider bar, is a reference
number which varies from 0 to 4095 representing the pole/zero adjustment
range. The values 1 to 4095 represents a time constant range of 1.7 ms to 40
µ
s. The value “0” can only be set manually; this setting is for no
compensation which represents infinity required for Reset type preamps.
The Pole/Zero value for successive Auto Pole/Zero initiations may vary
slightly. This is normal and results from statistical variation associated with
the algorithm and system baseline noise.
If Reset Mode was selected, the four digit value will be set to “0”, which is
required for proper operation with reset-type preamps.
6.
Manual Fine Tuning Using the Pole/Zero Slider Bar
With the RC Pole/Zero Mode selected, the Pole/Zero may be adjusted
manually or the Pole/Zero compensation value, resulting from the automatic
operation, may be trimmed by adjusting the associated slider bar on the Filter
Device Adjust screen. This operation permanently overwrites the Auto value
and may be used to fine tune the Pole/Zero setting to optimize performance
at high rates. For additional discussion on manual Pole/Zero adjustment,
refer to “Manual Pole/Zero Matching” on page 41.
7.
Verifying Pole/Zero Accuracy
The precision of the Auto P/Z operation can be verified by observing the
reconstructed Trapezoid signal on the Monitor Output. Observe the trailing
edge of the Trapezoid signal as it returns to the baseline, it should return with
no over or undershoot. Set the oscilloscope vertical range to an appropriate
sensitivity. Use a Canberra Schottky Clamp Box, Model 1502 or equivalent
to prevent oscilloscope overload.
For additional discussion on Pole/Zero verification and manual adjustment,
refer to “Manual Pole/Zero Matching” on page 41.
Manual Pole/Zero Matching
At high count rates, the Pole/Zero (P/Z) matching adjustment is extremely critical for
maintaining good resolution and low peak shift. For a precise and optimum setting of
the P/Z matching, a scope vertical sensitivity of 50 mV/div should be used.
With correct P/Z, spectral peaks will appear symmetrical;.while under compensated
P/Z will produce low energy tailing. Over compensated P/Z will produce high energy
tailing. An example of each condition is shown in Figure 20.
User’s Manual - ICN 9231014G
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Detector Matching
