User manual

Table 1-1. Control Relay Functions
Connects Cable Test or one-wire LO REF terminal to the
one-wire LO COM terminal.
Connects upper 32 channels (banks 4 - 7) to analog bus.
Connects lower and upper analog buses together.
14 Getting Started Chapter 1
Basic Operating
Modes
The E1460A uses the channel and control relays on the switch card to
perform four basic operating modes: one-wire, two-wire, three-wire, or
four-wire as shown. Connections to the analog bus (for multimeter
connection) are provided on both the relay switch card and terminal module.
One-wire Mode Switches either the HI or LO terminal of a channel in banks 0 through 7 to
the one-wire HI COM terminal. One-wire LO COM is switched to the
one-wire LO REF terminal. Only one channel can be switched (closed) at 
a time. A maximum of 128 one-wire channels can be switched. SCAN go
es
through all channel relay lows. Then, control relay 0990 switches and SCAN
goes through all channel relay highs.
Two-wire Mode Switches both the HI and LO terminals of a channel in banks 0 through 7 
to the HI COM and LO COM terminals. A maximum of 64 two-wire channels
ca
n be switched.
Three-wire Mode Switches both the HI and LO terminals of a channel in banks 0 through 3
to the HI COM and LO COM terminals. Th
is mode also switches the LO
terminal of the pair channel in banks 4 through 7 to the LO COM terminal. 
In addition, the low terminal of the pair channel in banks 4 through 7 can be
con
nected to the analog bus Guard terminal. Banks are paired 0/4, 1/5, 2/6,
and 3/7. A maximum of 32 three-wire channels can be switched.
Four-wire Mode Switches both the HI and LO terminals of a channel in banks 0 through 3
to the HI COM and LO COM terminals.
Also switches the HI and LO
terminals of the pair channel in banks 4 through 7 to the HI COM and LO
COM terminals. Banks are paired 0/4, 1/5, 2/6, and 3/7. A maximum of 
32 four-wire channels can be switched.
Control
Relay
Function
0990 Selects HI or LO terminal for one-wire switching.
0991
0992 Connects lower 32 channels (banks 0 - 3) to analog bus.
0993
0994
0995 Connects lower and upper common buses together
(
64-channel, two-wire operation).
0996 Connects analog bus Guard to the LO line, on the upper 
32 channels (banks 4 to 7).