Dear sirs
Hi
I'm student of Shiraz university (B.S. under graduating). I'm studying mechanical engineering.
I am doing a project on water level controller.
I have a tank that has an inlet and outlet.
The outlet valve is an ordinary valve that operator open and close verses he need. I think it is possible for the inlet we use valve
actuator that open and close with 4-20mA (current). I want to control the level by using computer.
I need help regarding the programming and the hardware (sensors) for water level detection.

Your faithfully
Mehdi Mohamad Hasani

 

We can’t help with the programming – but I’m sure many of the form members have an answer for you. For a continuous level sensor please check out:
"http://www.almegcontrols.com/":http://www.almegcontrols.com/ go to products – continuous - and check out the pdf file. The units are available with 4-20, 3 wire voltage or resistive two wire. (fuel sender type)

Thanks Bob Hogg

 

Depending on the size of tank, volume of flow available in and out, and accuracy required you can do a number of things. Easiest is a pair of flygt float switches, one to open and close a motorized valve, and one to alarm if it gets too full and the valve fails open.

If you require more accurate level control, want to avoid water hammer etc, I would go to an analog water level sensor, a PID controller, and a modulating valve. With a bit of playing around, you should be able to get the valve to open quickly when tank is drained quickly. Alternately, a small outflow would cause only a small opening of the valve.

Simple PID controllers are available from the HVAC industry, much cheaper than a PLC.

Hope this helps.

 

A multitude of ultra sonic level sensors exist that can be used for this simple application. ThermoMeasureTech, Milltronics, Drexelbrook,Endress & Hauser to name a few. All have devices that output 4-20mA signals that you
can use to assist in control.

L.Kolbert.

 

Dear Hasani,

There are a few ways. We have done several similar student projects in
Singapore and elsewhere.

1. Pressure transmitter (level connection) with 4-20 mA output to controller with 4-20 mA output to positioner on control valve actuator. The controller connects to the PC through interface of some protocol on RS485
- This has been done for decades and is not an interesting project

2. Pressure transmitter (level connection) with HART communication and built-in controller with 4-20 mA output to positioner on control valve
actuator. The transmiiter connects to the PC through interface of the HART protocol
- This is a bit interesting

3. Pressure transmitter (level connection) and positioner on control valve actuator both with H1 FOUNDATION(tm) Fieldbus communication. Both connect to the PC through a linking device via HSE FOUNDATION(tm) Fieldbus on Ethernet.
- This is very new and interesting

Best regards,
Jonas Berge