©Copyright MAC Instruments 2005. All Rights Reserved. MAC155 Rev. 12
Pg 15
PROBE JUNCTION BOX
A small user supplied junction box with terminal strips is typically used to
connect the weather proof MAC155 probe cables to user supplied wires that run
back to the MAC155 controller.
The probe requires either 120V or 230V AC power (3Amps max.) and +/-15V
DC power (4 Amps max.). The AC and DC power to the probe usually comes
from the MAC155 controller. In order to keep the voltage drop in the DC wires to
less than 1.0 Volt, large size wire must be used. Refer to the wire size schedule
on the MAC155 wiring diagram.
When the probe is located at a considerable distance from the controller, the
installed cost of the wiring can be high enough to make it cost effective to mount
DC power supplies near the MAC155 probe. In some cases it is also desirable to
obtain AC power from a source close to the MAC155 probe rather than running it
from the MAC155 Controller.
In some installations it is desirable to replace the shielded twisted pair RS485
signal cable that usually runs between the probe and controller with a fiber optic
cable. This provides a high level of electrical isolation in cases where it is
needed. The fiber optic cable will increase the maximum range from 1000ft
(300m) to 3000ft (1000m).
MAC155 PROBE JUNCTION BOX OPTION
The MAC155 probe junction box option is a pre engineered probe connection
system that allows any of the above described situations to be conveniently
handled.
The MAC155 probe junction box is a NEMA 4X stainless steel enclosure
measuring approximately 8”X10”X4”. Refer to the MAC155 probe junction box
outline drawing, and wiring diagrams at the end of this manual for details.
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