Confused about VI

[paulhs94]

Hello all,

I have a VI where I have to control the temperature of a water tank. If the temperature goes above my maximum threshold, the temperature has to be lowered at the rate of 2 degrees per second until it reaches the average temperature of the minimum and maximum threshold and if it goes below my minimum threshold, it has to be raised by 2 degrees per second until it reaches the average temperature of the minimum and maximum threshold. How would I go about this? I'm really confused as to how I can raise the temperature by two degrees per second and lower it by two degrees per second. Any help would be appreciated. Thanks for reading.

[johnsold]

Is this a simulation or a real tank? What is the source of power (or hot and cold water) to be used in changing the temperature. What is the volume of water in the tank? Does the rate of temperature change need to be the same regardless of the amount of water in the tank? What is the range of temperature setpoints which will be used? Does the system need any over-temperature, under-temperature, or low water safety controls?  How is the water mixed or stirred so that all the water in the tank is close to the same temperature? What can cause the temperature of the water in the tank to change, other than the controlled inputs? How fast can those changes be?

And probably several other questions which did not occur to me yet.

Lynn

[paulhs94]

This is a simulation. It is a very basic VI, I do not have to know the volume of water in a tank because it is irrelevant. My maximum threshold is 100, my minimum threshold is 0. Nothing else can cause the water temperature to change because I am the only one who controls the temperature. I have the temperature as a numeric control so I can set it to whatever temperature I want. The program has to decrease the water temperature by 2 degrees per second if the temperature goes over 100 until it reaches the average, or if the water temperature goes below 0 it has to increase by 2 degrees per second until it reaches the average. The rate of temperature change must be a constant 2 degrees per second if it passes either of the thresholds.

[johnsold]

For something like this it is usually best for you to post your VI. Set the controls to typical values and make them default, then save and post that VI. Also tell us what you expect the results to be for the values you have set.

We can see what you have tried and suggest fixes or improvements. At the same time we can help you learn to use LV more effectively.

Lynn