Description and function
6
Rivo™ I Controller EN
31
Evoqua Water Technologies GmbH | W3T597263 Issue 01-0624
Operating principle of the ratio control:
Using the flow sensor with linear mA output signal, the
flow rate in a pipe is measured and the dosing rate
adjusted proportional to the flow. Settings for the flow sig-
nal are made via the “Application Bar”.
The ratio between control variable flow Wq and dosing
output is defined via the internal dosing factor.
The setting range allows values from 0 to 400 %.
If a positioner with feedback signal is used as a dosing
output, it can be linearized with several data points. At
least two points are necessary(0/100%). They can be cal-
ibrated manually or via the automatic positioner calibra-
tion function (see Chapter 10.8 Positioner calibration).
If a positioner with position feedback Ym is used, it is
essential to calibrate the position during startup. 2, 3, 6 or
11 data points with firmly defined data points are possible.
The number can be defined under:
Menu - Dosing > Ym calib. points
The data points must then be set:
Menu - Dosing - Ym calib. manual
In this operation mode, the controller output is calculated
as follows:
NOTICE
If the measuring range end value of the flow meter is not
equal to the actual, maximum flow, the flow signal must
be adjusted. To do this, an upper calibration point input
is entered as an mA value corresponding to the mA sig-
nal at maximum flow. A further value, to be displayed as
max. display value for the flow rate, must be entered as
upper calibration point output.
For example:
Measurement range flow meter = 5000 l/h
Actual maximum flow rate = 2500 l/h of the controlled
system (corresponds to 50 % of the measuring range of
the flow meter)
Input signal = 4 ... 20 mA (output, flow measurement)
Upper calibration point input signal = 12 mA (corre-
sponds mathematically to 50% of the mA signal range)
Upper calibration point output signal = 2500 l/h
Yout = Wq x DF
Wq Control variable 1 flow rate in %
DF Set dosing factor in %
NOTICE
If a dosing factor >100% is selected, the maximum dos-
ing quantity is already reached at flow rates of less than
100%, i.e. it may not be possible to reach the desired
dosing quantity with higher flow rates.
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