Burkert Type 8611 - Manual (Page 48)

48
FunctionsoftheConfigurationLevel
12.3.1. RATI - selection of external sensors for ratio control
A ratio control can easily be implemented by combining the compact controller Type 8611 with flow-rate fitting
S030 and a second flow-rate sensor.
In a ratio control, the controlled flow-rate Q
1
is adapted to the uncontrolled flow-rate Q
2
so that it corresponds to
a specified mixture ratio.
The flow-rate is measured for Q
1
using the Bürkert flow-rate fitting of Type S030
for Q
2
using a second external flow-rate sensor.
The following relation exists between Q
1
and Q
2
:
Q
1
= RFAC · Q
2
Q
1
: controlled flow-rate
Q
2
: uncontrolled flow-rate
RFAC: ratio factor
(for selection see chapter “11.6. RFAC - Ratio factor default for ratio
control”)
Example of a ratio control:
Selected ratio factor RFAC: 4, 00
Flow-rate Q
2
: 20 l/h
Control of Q
1
to: 20 l/h · 4 = 80 l/h
Schematic representation:
Controller setting:
MODE = RATI, FREQ, 4 – 20, FREQ
8611
Flow-rate Q
1
controlled
Flow-rate Q
2
uncontrolled
Flow-rate fitting,
Type S030
Fluid mixture
Q
2
Manipulated variable 4 - 20 mA
Frequency ( FREQ)
Figure 28: Ratio control using process controller Type 8611 (assembly directly on flow-rate fitting Type S030).
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Type 8611