Engineering; Implementing Volume Flow Measurement - Siemens QBM97 Series User Manual

3 Engineering

3.1 Implementing volume flow measurement

Value in registers
Example
Siemens
Building Technologies
In addition to normal (differential) pressure measurement, the QBM97.. provides
volume flow measurement (f.e. used with 3rd party controllers).
Flow is a volume per time. It is related to differential pressure according to the
following formula:
Flow measurement with QBM97.. is set up in an application as follows:
1. Write vendor specific k factor of the measured device into register 4x0083
(sensor 1) and/or 4x0093 (sensor 2). Permitted range 0...1500.
2. Select requested unit in register 4x0084 (sensor 1) and/or 4x0094 (sensor 2).
Selectable are m /h, m
3
 QBM97.. calculates the flow value.
3. Read out the flow value from registers 4x0081/4x0082 (flow low/flow high of
sensor 1) resp. registers 4x0091/4x0092 (flow low/flow high of sensor 2).
The two registers exist because of mathematical reasons: The QBM97.. works with
a high 16 bit and a low 16 bit register.
● Value in register "flow high" = 12
● Value in register "flow low" = 35012
Calculation:
12*65536 = 786432
786432 + 35012 = 821444
With scaling (0.01) the end value = 8214.44m3/h.
Implementing volume flow measurement
/s or l/s.
3
Engineering
3
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A6V11478123_en_a
2019-02-01