IM 61A YHC1-E-A
3rd Edition: May 2008
Page 15 of 34
HART
®
Communications with the YHC 4150X
Overview
The YHC 4150X HART communicator provides device specific HART communication functions that
allow the user to poll, configure and maintain supported HART field devices. The YHC uses Universal,
Common Practice and Device Specific commands to facilitate communication with a HART field device.
Use the YHC to commission devices, for operational re-configuration needs, or maintain devices through
analog and sensor trim adjustments and many other features.
The YHC will communicate with any HART device through Universal and Common Practice Commands
using the standard Generic DOF (Device Object File) but must have the DOF for a specific HART device
installed before it can execute Device Specific Commands. Consult the large and growing list of available
DOFs at
http://fibu.yokogawa-usa.com/yhc4150.html
by clicking on the “Available DOFs” link. When
HART device support for new devices becomes available, the YHC can be easily field updated via Internet
downloads.
Warning: To avoid damage to a PC serial port, do not connect the YHC’s HART leads to an AC powered
HART device while the YHC is on AC power and a serial cable is connected to a PC. Yokogawa
recommends disconnecting the HART leads from the YHC prior to any communication activity.
HART Commands
Three HART command types are used by the YHC to communicate with HART field devices. First,
Universal Commands
are primarily used to identify a field device by its model number and tag number and
to read process data from the device. This communication is referred to as “polling”. The YHC can poll any
Hart Device. Second,
Common Practice Commands
are used for calibration and maintenance functions that
are common to many devices. An example of this would be trims or adjustments for the devices’ analog
outputs. Third,
Device Specific Commands
are used to handle functions that are unique to a particular device
or manufacturer. Examples of these commands include sensor zero, sensor trim, calibration curve
characterization, density inputs required for calculations made by the HART device or other configuration
functions unique to the specific device.
HART Connections
HART connections are made using two standard banana jacks (3/4” center) located at the top end of the
YHC. Refer to the following diagram. Polarity is not a concern for HART connections, therefore, both jack
collars are black. Yokogawa supplies a HART lead kit (P/N ZA900529-00014) complete with mini-grabber
connections and a 250
Ω
load resistor with each model YHC.
For low load loops (less than 250
Ω
), a 250
Ω
resistor may be needed in the loop to insure reliable HART
communications. Yokogawa supplies a 250
Ω
load resistor in the form of a standard adaptor (P/N
ZA36821). Refer to the following diagram for connection details.
YHC 4150X with HART
®
HART
®
connections are standard
banana jacks (3/4” center)
