Siemens QBM97 Series - 3 Engineering; 3.1 Volume Flow Measurement Setup

Engineering
Implementing volume flow measurement
3
15 |
22
Siemens
A6V11478123_en_a
Building Technologies
2019-02-01
3 Engineering
3.1 Implementing volume flow measurement
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
3
/h, m
3
/s or l/s.
 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.
Value in registers
Example