Michell Instruments Promet I.S., Руководство пользователя

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Promet I.S. User’s Manual
52 97221 Issue 5, March 2017
APPENDIX B
MODBUS RTU
Once the protocol has been set the monitor will communicate in accordance with the standard
Modbus RTU protocol.
The
Read Holding Registers
command should be used to read the registers listed in the register
map. When two registers are listed in the table both registers must be read using a single command.
Note that the least signi fi cant word is sent fi rst, for example - for dew point - register 40517 is the
least signi fi cant word and 40518 is the most signi fi cant word.
It should also be noted that the actual address is that stated, minus 40000, i.e. 40517 is physically
517.
Example: Getting the dew-point value using Modbus RTU
Register Numbers:
Function Register Name Texmate ASCII Modbus RTU
BARG RESULT 254 40515/40516
Dew Point_C CH1 253 40517/40518
psig CH2 252 40519/40520
There is often an offset of -1 for the register address, depending on your software/PLC system. To
read the dew-point value software, read holding registers 516-517:
The highlighted value 0xFFFFFDE2 is a 32 bit signed integer .. so -542
There is a scaling multiplier of 0.1, so -542 x 0.1 = - 54.2°C which is the value shown on the monitor.