Owner manual

User's Guide _______________________________________________________________________
96 ___________________________________________________________________ M211659EN-B
APPENDIX B
MODBUS REFERENCE
This appendix describes the Modbus protocol implementation of the
GMW90 series digital transmitters.
NOTE
For more information on Modbus protocol, refer to the Specification and
Implementation Guide for Modbus Over Serial Line.
NOTE
Serial line settings such as baud rate are configured using DIP switches.
See section Configuration of Digital Output Models on page 21.
Table 42 Modbus Functions Supported by GMW90
Function Code
Name
03 (0x03)
Read Holding Registers
04 (0x04)
Read Input Register
06 (0x06)
Write Single Register
16 (0x10)
Write Multiple Registers
43 / 14 (0x2B / 0x0E)
Read Device Identification
Table 43 GMW90 Modbus Measurement Data Registers
Name
Metric float
Metric
integer
Metric
unit
Non-metric
float
Non-metric
integer
Non-metric
unit
CO2
0001…0002
0257 (×1)
ppm
6401…6402
6657 (×1)
ppm
RH
0003…0004
0258 (×0.01)
%RH
6403…0004
6458 (×0.01)
%RH
T
0005…0006
0259 (×0.01)
°C
6405…0006
6459 (×0.01)
°F
Td
0007…0008
0260 (×0.01)
°C
6407…0008
6460 (×0.01)
°F
Tdf
0009…0010
0261 (×0.01)
°C
6409…0010
6461 (×0.01)
°F
dTd
0011…0012
0262 (×0.01)
°C
6411…0012
6462 (×0.01)
°F
Tw
0013…0014
0263 (×0.01)
°C
6413…0014
6463 (×0.01)
°F
a
0015…0016
0264 (×0.01)
g/m3
6415…0016
6464 (×0.01)
gr/ft3
x
0017…0018
0265 (×0.01)
g/kg
6417…0018
6465 (×0.01)
gr/lb
h
0019…0020
0266 (×0.01)
kJ/kg
6419…0020
6466 (×0.01)
btu/lb
Values read from the integer registers must be multiplied with the
provided multiplier to get the actual value. All integer values are signed.