Modbus Server Supplement to User Manual - ENGLISH
66 SU_ModbusV2-8, 2015-03-02
8 Request of Additional Quantities
8.1 Channel-Independent Diagnostic Values
The absolute and relative difference values of measuring channel A and B are channel-independent diagnostic values.
They are available in blocks of 16 Modbus registers in a predefined address range.
The start address is 30000.
For the calculation of the Modbus register address, an offset is added to the start address of the channel.
For the calculation of the Modbus register address, an additional offset is added to the start address (see Tab. 6.3).
Determination of the State
The state depends on the state of the values of measuring channel A and B:
• If the state of the value of measuring channel A and/or B is "not available" or "failed", the channel-independent diagnostic
value has the same state.
• If the state of the value of both measuring channels is "ok", the state of the channel-independent diagnostic value is also
"ok" and the time since the last update is reset.
8.2 Additional Physical Quantities and HPI Quantities
Tab. 8.1: Offset of the channel-independent diagnostic values
value offset predefined unit of measurement
channel-independent diagnostic values
flow velocity - absolute 0 dependent on the value of measuring channel A
flow velocity - relative 16 %
sound speed - absolute 32 dependent on the value of measuring channel A
sound speed - relative 48 %
signal amplitude - absolute 64 dependent on the value of measuring channel A
signal amplitude - relative 80 %
SNR - absolute 96 dependent on the value of measuring channel A
SNR - relative 112 %
SCNR - absolute 128 dependent on the value of measuring channel A
SCNR - relative 144 %
Example: diagnostic value: sound speed - absolute
parameter: state
Modbus register address: 30000 + 32 + 0 = 30032
Tab. 8.2: Offset HPI
value offset unit of mea-
surement
data format
state of measuring channel
2
600 integer 16 bit
time since last update 601 s integer 16 bit
volumetric flow rate
positive flow direction 602 m³/h floating point number 32 bit
negative flow direction 604 floating point number 32 bit
totalizer for positive flow direction 606 m³ integer 32 bit
totalizer for negative flow direction 608 integer 32 bit
state
3
610 integer 16 bit
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