Liquid Dosing Control Manual
9.17.150 rev A – September 2020
Page
12
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34
2.2.8 Ratio dosing specific configuration settings
Ratio or Master/Slave control loop
In a Ratio or Master/Slave control loop, the Liquid Dosing Set operates in a Slave control mode
based on a measurement signal from an external flow meter, the Master signal.
The Master measurement signal is connected as an analog input signal.
Using the calculated Slave Factor, the Liquid Dosing Set doses the right amount of liquid as a
function of the Master measurement signal.
Electrical connection
Refer to the electrical hook-up diagram of the instrument for Analog Operation connection
instructions.
Depending on the type of actuator, the control signal is configured as 4 – 20 mA or 0 – 10 V.
The Master measurement analog signal needs to be configured in the same way.
Configure instrument for Ratio Control
Change control mode
Change Control Mode
- Write value 10 to parameter 12 – Control Mode
(Analog Slave Operation)
Calculate Ratio Control setting
The ratio control setting is defined as a percentage, the Slave Factor.
To determine the settings:
Master Flow Analog signal 4 – 20 mA or 0 – 10 V = 0 – 32000 = 0 – 100% of range.
- Read parameter 11 – Measure
(Measure of Master 0 – 32000)
Example
A Master Flow meter with a maximum capacity of 10,000 kg / h provides
an input signal of 16000 = 50%, therefore a measurement of 5,000 kg / h.
Determine the Slave Factor
Example
The ratio of liquid to be dosed is 1 : 1,000, for every 1,000 kg measured
in the main flow, the Liquid Dosing Set will need to add 1 kg of liquid.
The Bronkhorst controller is configured for 10 kg / h (Capacity Value)
Capacity Value Master
10,000 kg / h (100%)
Capacity Value Slave
10 kg / h (100%)
Ratio
1:1,000
At 100% Master flow, a dosage of 1:1,000 for 10,000 kg = 10 kg = 100%
of Slave capacity.
Slave Factor =
100
If Master meter measures 50% (5000 kg) and Slave factor is 100, then
the setpoint for the dosed amount of liquid will be 50% = 5 kg / hr.
