digiBASE
®
PMT Base with Integrated Bias Supply, Preamplifier and Digital Multichannel Analyzer 931003E / 0620
3.1.1. Inputs
ENABLE INPUT The SMA connector accepts a TTL signal, the function of which depends on
the Gate setting on the ADC tab under Acquire/MCB Properties... in MAESTRO.
! When set to Enable, if the ENABLE INPUT is low (<0.8V), real time, live time, and data
acquisition are stopped. When the ENABLE INPUT is left open or forced high (>2.0V),
real time, live time, and data acquisition is enabled.
! If set to Coincidence, when the ENABLE INPUT is low, real time and live time operate
normally, but no counts are stored in memory. If the ENABLE INPUT is high, normal
acquisition occurs.
! If set to Event, rising edges are counted by a 32-bit event counter. The contents of the
counter can be monitored on the Status tab under Acquire/MCB Properties... in
MAESTRO. Input impedance is 5 kÙ to +3.3V, protected to ±10 V.
USB Full-speed (12M bps), bus-powered USB 1.1 interface.
3.1.2. Special Performance Features
List Mode Acquisition If you need the ultimate in fine time resolution — especially important
for Homeland Security applications — the digiBASE features List Mode operation, in which
each valid input signal is converted to a digital value, which is transmitted to the computer along
with the time the event occurred. Time is measured to the nearest microsecond. Each event
causes a 32-bit word to be transmitted to the computer. The bits of the word are decoded as
follows:
Bit Description
31 (msb) TimeStampFlag (0 = Normal Data, 1 = Time Stamp)
30–21 Amplitude of the event
20–0 Time event arrived in units of microseconds
In addition, every second a “time stamp” word is transmitted. This time-stamp word is used to
track rollovers in the 21-bit time stamp in the normal data word.
Bit Description
31 (msb) TimeStampFlag (0 = Normal Data, 1 = Time Stamp)
30–0 Current time in microseconds
20
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