How to make a value decrease by time, intervals of one second

[Bebeto]

Hello I am working with an Agilent N5181A to send a command from my code. I have set up the frequency and now I want to be able to change the value for the amplitude. Right now I have a constant set to -30  and I want to replace it so that it goes from -30 to -80 in -10 intervals every second.

For example:

-30

-40

-50

etc

so that at the end I reach -80, I have attached a screenshot for better explanation, thanks.

[Dennis_Knutson]

Please stop posting to the wrong board. This is for NI Signal Generators - just like it says. Use the Instrument Control board.

Your question isn't even related to an instrument. All that you need is a shift register and a subtract function. Initialize the shift register to -30 and subtract 10 each loop. Stop the loop when the minimum value is reached. If your loop iterates once a second, that's all you have to do.

Message Edited by Dennis Knutson on 10-27-2009 03:13 PM

[Bebeto]

How do I connect this to the Agilent PSG MXG Series Configure Power.vi? from where to I take the output to the input of the power.vi?

Also is the control STOP supposed to be a random one? 

[Dennis_Knutson]

The x-y value would be your amplitude setting. Your existing code would have to be placed inside a loop likethis.

Of course the stop is not 'random'. The loop stops when the final value is reached.

Why don't you simply create a VI like this to get an idea of how it works. It's very, very basic LabVIEW programming.

[Bebeto]

If I  place the whole code inside the loop doesn't this affect the frequency that I am setting up?

the Stop control do you get it from right clicking on the loop? since it does not seem to be working correctly when I run it, it just stays on -40.

[Bebeto]

I am not an expert that is why I am asking

but if I just want to change the value for the constant, (the one attached and enclosed in red) do I need to set the while loop for the whole code?

[Dennis_Knutson · Accepted solution]

The frequency setting is whatever you pass to the frequency control value. How often you update the voltage is dependent on the wait time. You said you wanted intervals of 1 second. That's why I used 1000 msec in the example. Obviously you would not need to put the whole code in the loop. Just the voltage function and whatever else that you need (i.e. some measurement).

The stop control is a control. If you do not know how to create a control on the front panel, you might want to go back to the very basic LabVIEW tutorials and review them.

The stop value is whatever you want. You said you wanted to have the values decrease from -30 to -80. If that is what you want, use a value of -80 in the control. If you want to stop at -90, enter that.

[Bebeto]

thanks for the explanation