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AM16/32B Relay Analog Multiplexer

"4 X 16" Mode

COM H (ODD)

COM L

COM H (EVEN)

COM L

ODD H

ODD L

EVEN H

EVEN L

SHIELD

SENSOR SHIELDS

COM

CR23X/

CR800/

CR850/

CR1000

21X/

CR7

CR10(X)

CR3000/

CR5000

EX E E VX

H H H H

L L L L

FIGURE 16. Full Bridge Measurement

6.4 Full Bridge Measurements

Sensor to Multiplexer wiring – With panel switch set to “4x16” mode,

excitation, ground, and the two signal leads may be connected to one

input SET (Figure 16).

Multiplexer to Datalogger wiring - COM terminals are connected to a

datalogger excitation channel, a differential analog input channel, and

an analog ground. Up to sixteen full bridges may be multiplexed

through the AM16/32B.

A problem with making full bridge measurements with this

configuration is that the resistance of the lead wire and multiplexer

relays can cause a voltage drop, reducing the excitation at the bridge.

The following section describes a configuration that compensates for

this by measuring the excitation at the bridge.

6.5 Full Bridges with Excitation Compensation

Sensor to Multiplexer wiring – With panel switch set to ”4x16” mode

you are 2 lines short for a six wire measurement. One solution is to

multiplex the four signal wires through the AM16/32B, but bypass the

AM16/32B with excitation and ground wires. This means that the

sensors will be excited in parallel which causes a higher current drain,

possibly enough to exceed the current available from the datalogger's

excitation channel. Alternatively, the excitation and ground leads can

be multiplexed through an additional AM16/32B allowing the sensors

to be excited one at a time (Figure 17). In this case the 12V, GND,

CLK, and RES lines of the second multiplexer are wired in parallel

with those of the first, effectively widening the multiplexer to “8x16”.

Multiplexer to Datalogger wiring - Four leads from the COM ODD,

EVEN terminals connect to two sequential differential analog

channels in the datalogger. Excitation and ground are multiplexed by

the second AM16/32B. Both multiplexers can be reset and clocked

by the same control ports and/or excitation channels to simplify

programming.

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