auto-tuning of gauge

[rohini_basu]

Hello

I am working on a gas mixer with three mass flow controllers. The UI which i am developing with LABVIEW contains a gauge for specifying the total flow of the three gases and three other guages for three separate gases which denote the ratio of the amount of the respective gases that shouldto be controlled by the individual mfc's. Now the problem is these ratio gauges have to be auto-tunable. Like, for xample, if i change the ratio for gas1, the other two ratios will adjust among themselves to keep the total flow constant. I am unable to find a solution for this because in C we use variables for denoting the change in one number while in labview we dont have such privileges. So can you suggest me a simple way out for the solution of this problem.

Thanks and regards

[_Ian_]

We need a bit more info... do you want to change the value displayed by an indicator, the range of values the gauge can display, the control output to the MFC?

I'm sure it can all be done without much difficulty, and I'd be surprised if not having "privileges" is really the case.

Can you elaborate a little?

[rohini_basu]

Suppose there are 3 ratio gauges A, B and C. I have given the total flow as say 15units and I have set the ratio in A as 3, in B as 5 and in C as 7. Now I changed the ratio in A to 4. So B and C will auto-tune among themselves and will increase and decrease correspondingly and the changed value will be shown in the front panel. I am attaching the screenshot of the front panel.

[_Ian_]

You could use an event structure to look for a change in the value of A.

Then, when A changes, read its value and the value of total flow and calculate the new values of B and C using whatever algorithm you require. Write the values for B and C to the user interface by wiring it to their terminals (or perhaps to a local variable).