OZONE ANALYZER BMT 964 Manual, Rev. 04/2021
56
Function Code 8 – Diagnostics
This function code provides some diagnostic tools for MODBUS communications. The query
contains a sub-function code defining the diagnostic action to be taken:
Sub-Function Description
0 Return Query Data, (2 bytes only!)
10 Reset Error Counters
12 CRC Error Counter
13 Exception Counter
Return Query Data is a simple loop-back test. The BMT 964 will echo the message sent to it.
Please note, that the data field of this query should be two bytes long. Both CRC Error Counter
and Exception Counter will start at 0 when the instrument is switched on.
Function Code 16 (10h) – Write multiple Registers
This function code provides means to configure the instrument. Float formatting is the same as
for function code 3.
Start Register Length Format Description
1 1 Word Set Ozone unit:
0: g/Nm
3
1: %wt/wt
2: ppmv
3: g/m
3
(without pressure and temperature com-
pensation, for AQ only)
4: ppm (for AQ only)
2 2 Float Low Alarm Limit (in set unit)
4 2 Float High Alarm Limit (in set unit)
6 1 Word Molecular weight of carrier gas?
0: Oxygen : 31.9988 g/mol
1: Air: 29.0 g/mol
7 1 Word
Autozero Interval in hours (max. 99, if 0: no
Autozero)
If parameters outside of the range given in the table above are used, or Low Alarm Limit is set
higher than High Alarm Limit, or High Alarm Limit is set lower than Low Alarm Limit, the in-
strument will reply with an exception 4.
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