Campbell Scientific AM16/32B Relay Multiplexer - Manual (Page 47)

AM16/32B Relay Analog Multiplexer
7. er ement Considerations
Lengths — Longer sensor-to-AM16/32B leads result in greater
d and capacitively coupled voltages (cross-talk) between cable wires.
nimize capacitive effects, Campbell Scientific recommends the use of
g having Teflon, polyethylene, or polypropylene insulation around
dual conductors. You should not use cables with PVC insulation around
idual conductors (PVC cable jacket is acceptable). It may also be
sary to program a delay within the measurement instruction allowing time
for lead wire capacitances to discharge after advancing a channel, before the
measurement is made. Please consult the Theory of Operation section of your
datalogger manual for more information.
Earth Ground — The AM16/32B’s ground lug should be connected to earth
round via an 8 AWG wire. This connection should be as short as possible.
e AM16/32B also connects to earth ground via the datalogger. The lead
re that connects the datalogger power ground to the AM16/32B power
hes this connection. The installation/maintenance
section of rmation on grounding
procedures.
pletion Resistors — In some applications, it is advantageous to place
sistors at the datalogger terminal strips. Certain sensors specific
ltiplexers are available from Campbell Scientific. Examples
oisture probes and thermistor probes. Please consult Campbell
r ordering and pricing information.
Contact Degradation — Once excitation in excess of 30 mA has been
multiplexed, that channel’s relay contacts have been rendered unsuitable for
rther low voltage measurement. To prevent undue degradation, it is
advisable to reserve certain channels for sensor excitation and employ other
s for sensor signals.
8.
The stand operated in an indoor, non-condensing
environment. If condensing humidity is present or if the possibility exists that
ltiplexer might be exposed to liquids, a water-resistant enclosure is
d.
e through Campbell Scientific
(models ENC10/12, ENC12/14, ENC14/16, and ENC16/18). They offer a
gree of protection against dust, spraying water, oil, falling dirt, or dripping,
noncorrosive liquids. These enclosures contain a mounting plate with 1-inch
hole grid suitable for mounting the AM16/32B. The enclosures have a cable
bushing to accommodate the sensor lines. These standard enclosures are rain-
tight, but not waterproof.
The enclosure lids are gasketed. The screws on the outside of the enclosure
should be tightened to form a restrictive seal. In high humidity environments,
user supplied foam, putty, or similar material helps to reduce the passage of
moisture into the enclosure via cable conduits.
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