OZONE ANALYZER BMT 964 Manual, Rev. 04/2021
55
Function Code 3 – Read Holding Registers
This code is used to request numeric information. The query specifies a start register and the
number of registers to be transmitted. Register size is 16 bits. Floating point and long values re-
quire two words to be transmitted. This means that a request for e.g. one single floating point
value has to have the data length field in the query set to 2. Floating point numbers are sent in
the standard 32-bit IEEE 754 format.
Start Register
Length
Format
Description
1
2
Float
Concentration (in set unit)
3
2
Float
Ozone range (in set unit)
5
2
Float
Pressure (in bar)
7
2
Float
Cuvette Status: Dirty value in %
9
2
Float
Pressure range (bar)
11
2
Float
Temperature (Kelvin)
13
2
Float
Low alarm limit (in set unit)
15
2
Float
High Alarm Limit (in set unit)
17
2
Float
Molecular weight of carrier gas
19
2
Float
Firmware Version
21
2
Long
Operating hours
23
2
Long
Serial Number
25
1
Word
Ozone unit:
0: g/Nm
3
1: %wt/wt
2: ppm
v
3: g/m
3
(without pressure and temperature com-
pensation)
4: ppm
26
1
Word
Front panel is set to display pressure in:
0: bar (1.0)
1: psi (14.50778)
2: Torr (750.0617)
3: MPa (0.1)
In parenthesis : Factor to calculate MODBUS
pressure value given in bar to set unit.
27
1
Word
Autozero Interval in hours, if 0: no Autozero
Function Code 5 – Write Single Coil
This code sets Low and High Alarms behaviour and allows execution of the zero command. Set-
ting to 1 activates function, 0 deactivates.
Start Coil
Description
1
Low Alarm Enable
2
High Alarm Enable
3
Low Alarm Latched
4
High Alarm Latched
5
Execute Zero
Sending a 0 to coil 5 will result in an exception code 4.
