Campbell Scientific AM16/32A Multiplexer - Manual (Page 15)

AM16/32A Relay Analog Multiplexer
4.2.1 COM Terminals
The four terminals dedicated to multiplexer-datalogger connection are located
under the blue “COM” next to the mode switch. The terminals are labeled:
ODD H, ODD L, EVEN H, and EVEN L. In “4x16” mode the AM16/32A
maintains the four “COM” terminals electrically isolated from one another. In
“2x32” mode the AM16/32A maintains an internal connection between ODD
H and EVEN H and between ODD L and EVEN L.
Common “ ” terminals are provided next to the COM ODD and COM
EVEN terminals. They bus internally to the other thirty-two “ ” terminals
on the AM16/32A and are connected at all times (i.e., not switched). Their
function is to provide a path to ground for sensor cable shields. A “COM
”
terminal should be wired to datalogger ground via the MUXSIGNAL cable (or
equivalent) shield according to the following table.
COM
ODD
4X16 H L
EVEN
H L
O N
MUXSIGNAL
SHIELD
CR10X CR23X CR1000
CR3000,
CR5000 21X CR7
CR800,
CR850
G
E1-E3 EX1-EX4 EX1-EX3 VX1-VX4 EXCITATION SWITCHED
ANALOG OUT
EX1-EX2
SE3 SE3 SE3 SE3 2H 2H SE3
SE2 SE2 SE2 SE2 1L 1L SE2
SE1 SE1 SE1 SE1 1H 1H SE1
FIGURE 5. Typical AM16/32A to Datalogger Signal Hookup (4x16 Mode)
4.2.2 Sensor Input Terminals
The terminals for sensor attachment are divided into 16 groups (panel switch
set to “4x16”) or into 32 groups (panel switch set to “2x32”). The groups
consist of four or two Simultaneously Enabled Terminals (SETs). With panel
switch set to “4x16” mode the blue channel numbers apply. The SETs are
numbered starting at 1 (1H, 1L, 2H, 2L) and continuing until SET 16 (31H,
31L, 32H, 32L).
In “4x16” mode the odd numbered terminals (example: 5H, 5L) are relay
switched to the COM ODD terminals while the even terminals (6H, 6L) are
switched to the COM EVEN terminals. When activated by the RES line being
high, as the AM16/32A receives clock pulses from the datalogger, each SET of
four in turn is switched into contact with the four COM terminals. For
example, when the first clock pulse is received from the datalogger, SET 1
(1H, 1L, 2H, 2L) are connected with COM (ODD H, ODD L, EVEN H, EVEN
L) terminals respectively. When the second clock pulse is received, the first
SET is switched out (channel 1 sensor inputs become open circuits) and SET 2
(3H, 3L, 4H, 4L) are connected to the four COM terminals. A given SET will
typically be connected to the common terminals for 20 ms.
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