Theory Of Operation; Channel Switching - Geokon 8032 Instruction Manual

1. THEORY OF OPERATION

The Model 8032 Terminal Board and Multiplexer expands the number of channels that can be
read by the 8600 Datalogger. Channel switching is accomplished by mechanical relays mounted
on the underside of the circuit board and the transducer connections are accomplished by friction
locking spring-loaded terminals mounted on the top side of the circuit board.
There are two varieties of 8032 board:
8032-E: Terminal Board only – typically used in conjunction with a 4999 Manual Switch Box
8032-C: Terminal Board with Multiplexer – typically used with the 8600 Datalogger.
Two switching configurations are supported, 16-channels of four conductors or 32-channels of
two conductors. For the 8032-C, these configurations are set by a DIP Switch on the top side of
the circuit board. A second DIP Switch selects whether the 8032-C is being used with a
datalogger or GK-403 Readout Box (obsolete model). For the 8032-E, these configurations are
determined by the 4999 Manual Switch Box.
To protect against lightning or EMI/RFI induced transients, each channel is protected by an
integrated lightning protection system, incorporating 230V tripolar plasma surge arrestors, 150V
bipolar plasma surge arrestors, 10uH inductors and 16V transient voltage protection diodes. See
Appendix A for complete specifications on these components.

1.1 Channel Switching

Figure 1 illustrates the DIP switch marked "SW1" on the top side of the multiplexer circuit
board. Switch position 1 is used for switching between 16 and 32-channel operation. If position 1
is set to OFF, the multiplexer is in 16-channel mode. If position 1 is set to ON, the multiplexer
is in 32-channel mode. In Figure 1, 32-channel mode is chosen:
The 16-channel four-wire switching configuration (Figure 2) is typically used to multiplex four-
wire sensors such as resistance strain gauge load cells. It is also used to switch connections for
instruments which have more than one sensor integral to them, such as vibrating wire pressure
transducers with an integral thermistor for measuring temperature.
ON
OFF
Figure 1 - Channel Selection Switch (Position 1 on SW1)
SW1
1 2 3 4
1