5
Connecting to the HART Device
Connect the two screw terminals to the HART device or HART loop. Microlink
provides electrical isola on between the HART loop and the PC. It is safe to
ignore grounding and polarity issues when making the HART connec ons.
The HART protocol requires a loop resistance of 230 to 600 ohms, typically
250 ohms. Refer to your equipment installa on instruc ons for details on
connec ng a HART master or con
fi
gura on device to the loop.
MicroLink HART modem connected
across the HART loop resistor.
MicroLink HART modem connected
across the HART device.
Two common methods for connecting the HART modem to a loop powered device.
Status LED Operation
When the modem is connected to the USB port with drivers installed, the status
LED will be green indica ng that the modem is ready. The LED will be red while
transmi ng or sending a packet to your HART protocol device. The LED will be
orange while receiving the HART reply.
LOOP
POWER
SUPPLY
HART
DEVICE
250Ω
LOOP
POWER
SUPPLY
HART
DEVICE
250Ω
Software Setup
Make sure your HART so ware is set to use the same serial COM port number
that the MicroLink modem is assigned to.
There are no hardware se ngs required by the MicroLink modem and modem
power is provided by the USB port. All other se ngs, such as BAUD rate and
parity, are taken care of by your HART so ware.
