41-621.1 HART
®
to Modbus
®
Adaptor Operating Manual
37
12.
Additional LevelMaster Commands
12.1.
Purpose
This procedure instructs how to configure the HART to Modbus Adaptor (HMA) to support the
additional Modbus LevelMaster protocol commands implemented in the HMA.
Using this procedure, the Number of Floats (UxxF?) can be read from the attached HART device and
the Level Offset parameter can be read (UxxOL?) and changed (UxxOLxxxx?).
Note that the returned value for Level Offset, as well as the value for writing to the device, is multiplied
by a factor of 10. For instance, a value of 0015 in the UxxOL? command represents a value of 1.5 in the
HART device. This is to allow a more precise adjustment capability within the context of the command
being limited to whole numbers.
12.2.
Equipment
Item
Manufacturer
Model
HART to Modbus Adaptor
MII
031-2859-001
RS485 Communications cable
FDTIchip
USB-RS485-WE
Termination resistor
-
120
Modbus host application
www.modbustools.com
Modbus Poll
Terminal v1.9b application
hw-server.com
Version 1.9b - 20040204
Power Supply
-
20-24V, 0.5A
Level transmitter
MII
Model 706
Probe
MII
Model 706 compatible
12.3.
Setup
Connect the HMA to a power supply via the power terminal block. Connect an RS-485 communications
cable to the RS-485 terminal block of the HMA, with the Receive/Transmit Data+ A lead (orange) on
the positive terminal and the Receive/Transmit Data
–
B lead (yellow) on the negative terminal.
Connect a 120
resistor between the two RS-485 terminal block positions. Connect the other end of
the cable to a PC which has a Modbus host application. Connect a Model 706 level transmitter to the
HART loop terminal block of the HMA. Set the HART Poll Address of the Model 706 device to 3. Note
that other Magnetrol HART transmitters and HART poll addresses can be used.
12.4.
Procedure
12.4.1
Using Procedure 1, ensure that registers 3000 through 3007 of the HMA match the values
shown for the Modbus LevelMaster protocol default settings. Refer to Appendix H for the
HMA Communication settings. If the settings do not match, double-click on a value that
needs to be changed to open the Write Single Register dialog, enter the new value, and
then click on Send.
Содержание Jupiter JM4
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