2 The Interface Solution Experts
4-wire/2-wire HART®Isolators
HIT/HIX
1HART is a registered trademark of the HART Communication Foundation.
Introduction
The Moore Industries’ 2‑wire, loop powered HIX
HART®Isolator, and its 4‑wire, mains powered
variant, the HIT, are compact, DIN‑rail mounted “loop
add‑ons”. They both are used to break the common
electrical (galvanic) path between a HART transmitter
and one or more receiving devices in a process
instrumentation loop.
About this Manual
Wherever you see a “WARNING”, “Caution” or “Note”
pay particular attention.
WARNING ‑ Hazardous procedure or condition that
could injure the operator.
Caution ‑ Hazardous procedure or condition that could
damage or destroy the unit.
Note ‑ Information that is helpful for a procedure,
condition, or operation of the unit.
HIT/HIX Description
The HIT and the HIX:
· Safeguard I/O cards from surges, spikes
and transients. Add the 500Vrms isolating
capability of a HART Isolator to a loop to
break the common (galvanic) path that can
pass dangerous overloads from DCS to HART
transmitter to PLC and vice‑versa. This
hazard is common—even when a transmitter
and DCS are supposedly “isolated” already.
· “Isolate” areas of an application. Ease
maintenance complications by using the
4‑wire HIT to maintain secondary loop
integrity while the primary HART master is
down for maintenance.
· Facilitate the “Sharing” of one HART
output—safely—with a secondary control or
recording device.
· Eliminate “Bucking” power supply
problems. Whenever more than one
4‑wire device provides power to the loop,
each power source (typically grounded with
differing potentials) vies for control. This
can cause both HART and analog signals to
uctuate, adversely affecting loop reliability
and accuracy.
Inputs and Outputs
Input to both the HIX and HIT is HART standard
4‑20mA with digital data superimposed. Both isolators
“pass” the conditioned HART signal through from
transmitter to receiver, and from receiver back to
transmitter. This “signal passing” is operationally
transparent to devices on either end of the loop.
Note:
The HIX and HIT are not HART-addressable
devices. They are “invisible” to the other HART
devices on the loop.
Transmitter Excitation
The 4‑wire HIT is also capable of providing power to
the transmitter it is isolating by virtue of its standard,
24V excitation output.
Power
The HIX is a 2‑wire isolator, drawing power from the
output leg of the loop (typically, the secondary DCS,
PLC, or ESS).
The HIT is a 4‑wire unit. It can be ordered in
congurations that draw power from either external
DC or external AC sources.
Moore Industries offers a complete line of instrument
power supplies ideal for use with the HIT. Ask your
local Interface Solutions Expert for information.
Housing
Both the HIX and HIT are housed in aluminum
DIN‑style housings. Older versions of the product
are housed in high‑impact, thermoplastic cases. The
compact housing styles can be mounted on either
G‑type DIN‑rail or Top Hat DIN‑style rail.
