HM-USB-PWR User Manual
MAN-1044 6/15/2017
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ISO 9001:2008 Certified
HART Loop resistor is built-in to the modem so an external resistor is not required for
this mode.
Modem Only
Connect the supplied HART cable to the “Modem Only” connector on the HM-USB-
PWR. The 24Vdc LED should be off.
Connect the Red connector to the positive (+) terminal of the HART Transmitter.
Connect the Black connector to the negative (-) terminal of the HART transmitter. Note
that the HART transmitter requires an external power supply and loop resistor in this
mode.
This mode is useful for communicating with WirelessHART devices that are battery
powered.
Power Only
Connect the supplied HART cable to the “Modem + Power” connector on the HM-USB-
PWR. The 24Vdc LED should illuminate.
Connect the Red connector to the positive (+) terminal of the HART Transmitter.
Connect the Black connector to the negative (-) terminal of the HART transmitter. The
HART transmitter is now powered. The HART Loop resistor is built-in to the modem so
an external resistor is not required for this mode when using an external HART modem.
Current Measurement
You can measure the loop current without breaking the loop. Simply connect your
current meter to the “Current” test points on the HM-USB-PWR.
External HART Modem Option
With the HM-USB-PWR operating in the Power Only mode, an external HART modem
or HART Communicator can be connected to the “HART” test points. The loop resistor
is built-in so no external loop resistor is necessary.
HART and Power Connections
Simply connect the modem to the HART transmitter observing power polarity. See
Figure 1.
Figure 1. HART and Power Connections
USB Connection
Connect the integral USB-A connector to any available USB port on your PC.
