Can we have continuous control out of valves?

[Spedy]

I am doing my final year project on "Liquid Level Control of Coupled Tank System".
Brief Description:
There is a inflow of liquid through a pump in the first tank. The first tank is connected to the second tank via  a orifice(a valve is used instead for labview simulation). The second tank has a outlet which is controlled by the user. I have to maintain the specified height in the second tank. A depth sensor is used to measure the height for both the tanks.
In LabVIEW, I could only find a valve with boolean control. Can I have a continuous control of the valve?
I would really be thankful if anyone could help me in any possible way.

[LV_Pro]

I'm not entirely clear regarding your question. When you say that you have only found a boolean "valve" I'm assuming that you mean a boolean control/indicator. I don't have access to the DSC package's controls/indicators so I don't know what is available there (that package provides a lot of tools used in the industry for industrial type control) but you can create a numeric control with custom graphics. The bigger issue is how you will actually control the physical elements of your project. How is the valve controlled? As to making it a closed loop, that isn't terribly hard, if you just need coarse level control the "feed back" equations can be fairly simple, for finer control of the levels you probably want to look into the various discussions of PID contol loops. There have been numerous threads regarding PID and custom control graphics in this forum.

While we (the forum) won't do your project, we will be happy to try and help if you run into problems.    It is very helpful to let us know what version of LabVIEW you are using, what addon packages you may have access to, what hardware you plan to control.

[Spedy]

I am using LabVIEW 7.1. I am using this software for the first time. For my project, I have simply modified an example present in "Find Examples" from Help menu. The example  is called  "Tank Simulation".
From this example, I have used the tank present here as my first tank which is perfectly controlled. The very first problem I faced was that I was not able to create an outlet from the first tank. So, I generated a inflow rate which pumps in liquid to the second tank through the valve. This should not have been the case. Moreover, the outlet of the second tank should also be controllable. I dont know how should I go about it.

I would be very thankful if you can kindly suggest a known way to carry on this project.
Thank You

[Pnt]

You can copy the input valve and connect it at the output of the tank.

It will be a boolean control , at which you will have full control.

When the boolean will be ON you should decrease the tank value, by a step for each itteration of the wile loop (according to time).

(It is the most regular. It can be according to other things)

Be more spesific if you need more info.

What kind of control you need, what are the parameters of your program, or post your vi.. even if it does not work