22May2002
Page
5
Run two wires from the controller
4-20mA Input
and
signal common
to the power/signal
terminals located on the bottom of the main circuit board. The power/signal terminals are
non-polarized.
NOTE:
The two power/signal wires must be isolated from other wires and should therefore
be
shielded
or run in metal conduit to avoid electrical pick-up. If a shield is used it
should run continuously from the controller electronics to the inside of the
transmitter junction box. The shield should be terminated at the controller
signal
common
but left floating (do not attach to anything) inside the transmitter junction
box to avoid ground loop interference. Apply electrical tape to exposed shield
inside junction box.
The
smarter
transmitter can be located up to several thousand feet (max. total loop
resistance = 500 ohms) from the controller electronics using 18 AWG standard copper wire.
V.
Transmitter Operation:
The
smarter
transmitter provides four magnetic switches to access information, test the
loop and calibrate the toxic sensor. The switches are activated using a magnet held directly
over the switch outside the junction box glass window.
