Strain Relief; Shielded Wire; Wire Length - Phonetics SENSAPHONE EXPRESS II User Manual

STRAIN RELIEF

Strain relief clamps are provided on the Express II enclosure to prevent wiring from being pulled
from the circuit board or damaged when passing through the enclosure. To use the strain relief,
thread wires through the clamp and the clear rubber bushing. Position the bushing in the clamp
and tighten the screws on either side so that the wiring does not move. See Figure 9 below:

SHIELDED WIRE

Express II is designed to work in most installations without the need for shielded wire. How-
ever, 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 inaccu-
rate 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.
®
14 Sensaphone Express II User's Manual
top plate
clamp screw
bottom plate
clear rubber bushing
wiring
Figure 9: Strain relief clamp