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
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
Pressure setting default
value
Pressure setting
temporary value
Molecular weight for
ppm
w
calculation
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
Standard filtering on/off
Extended filtering on/off
1 = Extended filtering on
Automatic chemical purge on/off
See configuration register
Start-up chemical purge on/off
Chemical purge in progress
1 = Purge in progress
(write 1 for manual start)
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.
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