- Variable area flow meter, range 100-1000 l/h
- Differential pressure electronic transmitter
- Pneumatic control valve
- Pressure gauge, range 0-2.5 bar
- Power supply light
- 2measurement terminals for the 4-20 mA input signal of the controller
- Microprocessor controller
- 2measurement terminals for the 4-20 mA output signal of the controller
- Transparent plastic tank, capacity 5 liters
Description of apparatus:
The unit enables to study the automatic level control using a line provided with tank, a control valve, a differential pressure transmitter and a PID controller. The system is provided with specific supervision software, Mod. SWLCB/ EV, that enables its use from the P.C. The bench can be connected in parallel to other automatic control benches (Mod. FCB/EV, TCB/EV and LCB/EV).
Experiments done on it:This unit used to control the level of water inside the tank.
In this unit, the PID control is made on the water level inside the tank D1. The control device consists in a pneumatic valve that, according to the signal from the PID controller, adjusts the inlet water flow rate to the tank and consequently the level. The electronic transmitter, LT1, measures the pressure at the base of the tank (directly proportional to the level) and sends the PID electronic controller a 4-20 mA electrical signal proportional to 0 - 500 mmH2O.
The signal sent by the transmitter LT1 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 electropneumatic converter into a pneumatic signal that controls the valve opening level.
The signals at the input and output of the PID controller can be measured with a milliammeter using the proper terminals set on the board. The pneumatic output signal from the I/P converter can be read directly on the pressure gauge set on the board. The controller is pre-set to PID mode (proportional + integral + derivative).