ORTEC Easy-MCS, Руководство пользователя по оборудованию

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931054C / 1213 1. INTRODUCTION
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times is recorded in the MCS memory. By design, the MCS can accept multiple stop pulses in
each scan. The channel numbers in memory can be calibrated to read in terms of round-trip flight
time, or in distance to the reflecting object. Summing the spectra from multiple laser flashes
improves the signal-to-noise ratio.
1.4. A Closer Look at the Easy-MCS
An Abundant Choice of Time Ranges
The Easy-MCS employs a crystal-controlled clock with 100 ppm accuracy and high-speed
digital electronics to achieve a wide range of accurate operating parameters. With the dwell
time per channel selectable from 100 ns to 1300 seconds, and a scan length variable from
4 to 65,536 channels, time scans can be selected ranging from 400 ns to 2.7 years.
No Dead Time Between Channels, and Zero End-of-Pass Dead Time
Easy-MCS employs sophisticated digital circuits to eliminate the dead time between chan-
nels that is typically encountered in lower-performance MCSs. The result is absolutely no
loss of counts and no double counting as the MCS advances from one time channel to the
next. Fast digital processing also ensures that there is no end-of-pass dead time before
starting a new scan.
Versatile Counting Inputs
Two different types of counting inputs make the Easy-MCS adaptable to virtually any source
of signals. The fast analog signal input (IN) accommodates both analog and digital signals
with pulse widths >3.5 ns and counting rates up to 150 MHz. The input discriminator thresh-
old is computer adjustable from
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1.6 V to +3 V in steps of 1.5 mV. This facilitates the pre-
ferential selection of larger pulses for counting and the rejection of noise. Triggering can be
selected for either positive or negative slope to match pulses of either polarity.
For counting rates up to 1 MHz with positive analog signals, Easy-MCS offers the pulse-
amplitude selectivity of the SCA (single-channel-analyzer) input. This input features two
computer-controlled discriminators whose thresholds can be set anywhere between 0 V and
+10 V with 12-bit resolution. Easy-MCS counts only the analog pulses that rise above the
lower-level threshold without exceeding the upper-level threshold. This input is ideal for
analog signals with amplitudes proportional to a measurement parameter, such as the number
of photons in a pulse. Pulse widths from 0.5
μ
s to 100
μ
s can be readily accommodated.
SCA Sweep Mode
The SCA Sweep mode makes the setting of the SCA thresholds quick, easy, and accurate. In
this mode the window width between the lower and upper SCA thresholds is held constant
(at 1/512 of 10 V) while the computer repeatedly sweeps the position of the window from
0 V to +10 V in 512 equal steps. In synchronism, the MCS repeatedly scans from channel