Meriam MFC 4101 HART, Инструкция оператора

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11
HART
®
Communications with the MFC 4100
Overview
The MFC 4100 HART communicator provides device specific HART communication functions that
allow the user to poll, configure and maintain supported HART field device. The MFC 4100 uses
Universal, Common Practice and Device Specific commands to facilitate communication with a HART
field device. Use the MFC to commission devices, operational re-configuration needs, or maintain
devices through analog and sensor trim adjustments and many other features.
The MFC 4100 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
www.meriam.com for an up to date list of HART devices with device specific support.
The list is found under “Available DOFs” button on the home page. When HART device support for new
devices becomes available, the MFC can be easily field updated via Internet downloads.
HART Commands
Three HART command types are used by the MFC 4100 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 MFC 4100 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
MFC 4100. Refer to the following diagram. Polarity is not a concern for HART connections so both jack
collars are black. Meriam supplies a HART lead kit (P/N A36744) complete with mini-grabber connections
and a 250
Ω load resistor with each model MFC 4100.
For low load loops (less than 250 Ω ), a 250 Ω resistor will need to be added to the loop to insure reliable
HART communications. Meriam supplies a 250 Ω load resistor in the form of a standard adaptor (P/N
A36821). Refer to the following diagram for connection details.
MFC 4100 with HART
®
HART
®
connections are standard banana jacks (3/4” center)