PID control VI

[alexb]

hey guys,

I need your help. I'm working on a project - level control in a tank with water.

I suppose to control the level of the water , for example - the user can choose the height he wants the water to fill the tank , and a pump starts to pour water into the tank.

I work with the PID VI. The user can choose how to control the water with the controllers - P , Pi , Pd or the combined PID.

For example , the P control works like the equation m=P*e

m - stands for the strengh of the water pumping

e - stands for the error - difference between the height I want , and the height found in the tank.

p - is a constant

As bigger the difference between the wanted height and the found height , as stronger the strengh of the pumping.

While the tank is being filled , the pumping suppose to get wicker until it stops.

This algorithm that I wrote shows :

The user chooses the set point - the height he wants.

The DAQ measures the height - (height * 100) / wanted height --> gives us the error.

But , while the tank is being filled , and the error is getting smaller , the pumping strengh stays the same.

P.S

I didn't use the entrance that called Process Variable in the PID VI. That's where I suppose to attach the "error". But when I do that the pump stops working.

Please help I don't know what to do... : (

It's my final project and I'm desperate.