- Electronic pH transmitter
- AISI 316 stainless steel feed tanks
- Variable area flow meters
- Mixer
- AISI 316 stainless steel reactor
- Variable area flow meters
- AISI 316 stainless steel collection tank
- Electrical supply light
- Microprocessor PID controller
- measurment terminals for the 4-20 mA signals at the controller input
- measurment terminals for the 4-20 mA signals at the controller output
- gear pumps
Description of apparatus:
The unit enables to study the automatic pH control in a reactor powered with two gear pumps.
Experiments done on it:
This unit used to control the pH inside the reactor R1. The control device consists in the pump G1 that, according to the signal coming from the PID controller, adjusts the flow rate of the basic solution at the input of the reactor and consequently the pH. The flow rate of the acid solution is fixed adjusting the flow rate of the pump G2. The control loop can be described as follows: the electronic transmitter, pHT1, measures the pH in the reactor R1 and sends the PID electronic controller a 4-20 mA electrical signal proportional to 2 - 12 pH.
The signal sent by the transmitter pHT1 to the PID controller is compared to the set point value set on the controller. At this point, the controller sends a signal to the output, function (PID) of the shift between the value of the process variable and the set point. This electrical signal is converted by an electronic card into voltage so that it controls the rpm (and so the flow-rate) of the pump G1. The signals at the input and output to the PID controller can be measured with a milliammeter using the proper terminals set on the board. The controller is pre-set in PI mode (proportional + integrative + derivative).