User manual

Introduction 1
User Manual 9
Independent Analog-to-Digital Converters
The analog-to-digital channels provide 24-bit analog-to-digital conversion of
up to two independent analog signals. The analog inputs can either be totally
asynchronous (have no relationship at all to each other) or synchronous
(separate signals, but logically related to the same START reference). To allow
asynchronous operation, each channel has separate Start/Stop switches,
status indicators, and controllable digital I/O. The analog input signal is
digitized by a continuously integrating A/D converter. This means that the
input signal is continuously applied to the converter's input, and because of
that, no portion of the signal is ever lost due to input multiplexing or the
sampling process.
Real-Time Control
The 35900 provides a set of real-time control functions for a host computer
system. These can be separated into two groups:
• Remote Control Bus
• Digital (TTL I/O) Ports
Remote control bus
The Remote Control Bus is a hardware interface that provides a set of defined
signals most frequently encountered in the laboratory environment. These
signals include START, STOP, READY and START REQUEST. The 35900 has
one Remote Bus per channel to allow for asynchronous operation. These
connectors are 9-pin "D-Type" female connectors each having eight
bidirectional (input/output) signals.
Digital (TTL I/O) ports
Each channel has a dedicated TTL I/O connector with 16 signal lines. Of the
16, eight are bidirectional configurable as inputs or outputs (for such
functions as valve control) and the remaining eight lines are input-only signals
(for such functions as bottle numbers).