The Hp 3421A Data Acquisition/Control Unit - HP 82479A Owner's Manual

Introduction
This loop structure provides several unique capabilities:
eo Auto address assignment, The HP-71 addresses the devices on the loop automatically.
oe Device capability identification. The HP-71 can match the appropriate device with the
command (for example, the printer with a FFF IHT command), so software can be written and
run without regard to addresses.
e Power ON/OFF control. The HP-71 can power peripherals on or off in order to conserve
battery life in remote, unattended applications.
e Automatic error checking. HP-IL allows data being transmitted on the loop to be checked
automatically for errors.
The HP 82401A HP-IL Interface allows the HP-71 to control devices such as printers, video interfaces,
disc drives, and instruments. The HP-IL module adds over 45 additional keywords to HP-71 BASIC,
which are used to control up to 30 devices, and through secondary addressing, up to 930 devices. Through
individual converters, the HP-71 can link to HP-IB, RS-232C, and GPIO devices.
The HP 82402A Dual HP-IL Adapter allows two HP 82401 A HP-IL Interfaces to be connected to the
HP-71, making sophisticated data acquisition/control systems possible. For instance, several HP-71
computers might share a loop with a host desktop computer, while maintaining individual loops for
dedicated data acquisition at individual production stations.
1.3 THE HP 3421A DATA ACQUISITION/CONTROL UNIT
The HP 3421 A Data Acquisition/Control Unit is a fully programmable instrument that combines
precision measurement capabilities with process control and monitoring functions. It can provide you with
accurate measurements of voltage, resistance, temperature, and frequency, or it can monitor and control
digital inputs and outputs (including actuators), or both. Standard equipment for the HP 3421A includes a
front panel display, a built-in § 1/2-digit voltmeter, a 10 kHz frequency counter, and an HP-IL
interface.
The HP 3421 A mainframe can accommodate up to three measurement/control option assemblies. The
following options are available:
e HP 3421A Option 020 - 8 Channel Multiplexer/2 Channel Actuator Assembly.
e HP 3421A Option 021 - 9 Channel Multiplexer/1 Channel Actuator Assembly.
e HP 3421A Option 022 - 10 Channel Multiplexer Assembly
HP 3421A Option 040 - Breadboard Assembly (with connnector block).
HP 3421A Option 050 - 8 bit in/8 bit out Digital I/O Assembly (with connector block).
Throughout the rest of this manual the term "multiplexer assembly" is used to mean either an option 020,
021, or 022 multiplexer. The term "digital I/O assembly" refers to the option 050 8-bit digital I/O
assembly.
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