Measurement Specialties PCI-QUAD-AC5 - Manual (Page 19)

PCI-QUAD-AC5 User's Guide Functional Details
Unconnected inputs float
Unconnected inputs typically float high, but not reliably. If you are using a PCI-QUAD-AC5 board for
input and have unconnected inputs, ignore the data from those lines. You do not have to terminate input
lines, and unconnected lines will not affect the performance of connected lines. Ensure that you mask out
any unconnected bits in software.
TTL to solid state relays
Many applications require digital outputs to switch AC and DC voltage motors on and off or to monitor
AC and high DC voltages. These AC and high DC voltages cannot be controlled or read directly by the
TTL digital lines of a PCI-QUAD-AC5.
Solid State Relays (SSRs) allow control and monitoring of AC and high DC voltages and provide 750 V
isolation. SSRs are the recommended method of interfacing to AC and high DC signals.
The most convenient way to use solid state relays and a PCI-QUAD-AC5 board is to purchase a Solid
State Relay Rack. The rack recommended for use with the PCI-QUAD-AC5 board is the SSR-PB24 from
Measurement Computing Corporation.
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