Vaisala GMW90 - Manual (Page 98)

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.