Variable in Case Structure range . . . or Similar

[Spartacus_1]

Hello all,

I'm using Case Structure to control an output.

Basically the Case is getting temperature feedback from DAQ, when the temperature reaches, let's say, 100C. It sends a command to turn OFF the heat for one minute or until it reaches 70C. After a minute or until it reaches 70C, it sends the signal to turn the heat back ON.

It's working perfectly while it's all hard coded.

However, I want to make create a control for both UpperTemp = 100C & LowerTemp = 70C so the user can change the upper & lower boundaries in Front Panel without the need to go and change it in Block Diagram.

Is there a way to code this as a variable in Case Structure . . . or any other method to do this?

Sorry if this is a basic question, i'm new to LabView.

[GerdW · Accepted solution]

Hi Spartacus,

so basically you want to create a control with a setpoint and a hysteresis. Maybe looking for words like these will result in useful threads…

No need for a case structure: you can use simple comparison functions (>=, <=) instead.

Creating an algorithm in some pseudocode may help too:

IF pv >= UpperLimit THEN state:=0 ELSE state:=state
IF pv <= LowerLimit THEN state:=1 ELSE state:=state

(pv is "process value", state is your desired output.)

Seems quite simple to create in LabVIEW!

Keep "state" in a shift register and create controls for UpperLimit/LowerLimit…