Sensaphone Express II - Manual (Page 24)

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Sensaphone ® Express II User’s Manual
Figure 9: Strain relief clamp
SHIELDED WIRE
Express II is designed to work in most installations without the need for shielded wire.
However, this does not apply to wire run outdoors or in conduit that has other noise-generating
conductors such as 60 Hz AC. It is strongly recommended that input wiring be run in a conduit
separated from AC power or output wiring. When wire runs are long or are in close proximity to
large power consuming, power generating or power switching equipment, it is recommended that
shielded wire be used.
WIRE LENGTH
Temperature—It is recommended that long wire runs be avoided when using a thermistor as
a sensor. A long run of wire could alter the resistance of the circuit therefore providing an
inaccurate temperature reading of the input. Below is a chart of recommended gauges and wire
lengths:
MIN WIRE GAUGE MAX WIRE LENGTH
#26 250 ft.
#24 700 ft.
#22 1500 ft.
#20 2500 ft.
Dry contact—The total resistance of the loop cannot exceed 50 Ohms. Use the appropriate
gauge wire for your application.
Analog current—Long wire runs will not affect the accuracy of the input because there is
constant current being driven through the sensor wire.
Analog voltage—Wire runs should be kept as short as possible to avoid voltage drops and noise
susceptibility. Use the gauge chart above as a guideline.
NOTE: All wiring should comply with section 17 of the UL requirements.
INSTALLING INPUT EXPANSION CARDS
To install an input expansion card:
1. Turn the unit off. Damage may occur to the motherboard or to the input card if installed while
power is still on.
2. Working from left to right, loosen the thumbscrews and remove the blank plate of the first
unused slot. See Figure 10.
NOTE: Always install cards side by side—do not skip a slot.