Vaisala HMT330 - Manual (Page 205)

Appendix C _________________________________________________________ Modbus Reference
VAISALA _______________________________________________________________________ 203
NOTE Basic status information of the HMT330 transmitter is also available with
the Read Exception Status function code 07. For details, see section
Exception Status Outputs on page 204.
Configuration Registers
Configuration parameter registers are used to configure the measurement.
Writing out-of-range values is silently ignored.
Table 43 Configuration Parameter Registers
Name Float Integer Valid Range
Pressure setting default
value 0769…0770 1025 (×1) 0…9999 hPa
Pressure setting
temporary value 0771…0772 1026 (×1) 0…9999 hPa
Chemical purge interval 0773…0774 1027 (×1) 10…2880 min
Molecular weight for
ppm
w
calculation
0775…0776 1028 (×0.001) 0…999.999
g/mol
If you modify the pressure setting repeatedly, modify the temporary
value at register 0771...0772 (1026) instead of the permanent setting at
register 0769…0770 (1025). Set the temporary value to zero to return to
the default pressure setting.
Non-metric units are not available on Modbus. If they are needed,
calculate the conversion outside the transmitter.
Configuration flags are used to select some basic options of the
instrument and to manually start the sensor operations.
Table 44 Configuration Flag Registers
Name Address Description
Standard filtering on/off 1281 1 = Filtering on
Extended filtering on/off 1282 1 = Extended filtering on
Automatic chemical purge on/off 1283 1 = Automatic purge on.
See configuration register
0773…0774 (1027).
Start-up chemical purge on/off 1284 1 = Start-up purge on
Chemical purge in progress 1285 1 = Purge in progress
(write 1 for manual start)
Sensor heating on/off 1287 1 = Sensor heating on
(optional feature)
Flags 1281 and 1282 are mutually exclusive.
Some of the configuration registers might not have an effect depending
on the instrument model and configuration.