Sending continuous signal from a While loop

[MEMS]

I am working on Differntial scanning Calorimeter. Using Labview 6.2.1, PCI 6211 and Keithley 2400 series. I have to send two analog outputs at same time and its amplitude changes every time but i have problems in the change of amplitude from a while loop. I have attached my file for reference. All i need is the amplitude for the buffer generator to change for every reading from the keithley instrument i get so that it changes the output voltage with respect to time. But its not happening. Is there any other way i can change the program in which i can send two outputs at the same time where the amplitude or the signal changes with respect to time.

[MEMS]

May be i can simply say that i want two outputs at the same time in which its frequency and amplitude changes with respect to time if i change it when the program is running as shown in the attached vi.

[Dennis_Knutson]

In neither of your programs can you update the analog out. In the first example, you continuously read the keithley until you hit the stop button and then the very last value is used to generate a waveform for each analog out and then another while loop just checks for an error until you click the second stop button. In the second example, you just generate waveforms and then do the monitoring. Once the while loop starts, you can't change the waveforms because your controls are no longer being read.

You need to understand data flow and you need to put the monitoring/pid/analog out in a single while loop.

[MEMS]

Hello Dennis,

  Thanks for the reply. The design of the second program which i have attached was helped by a National Instruments technical engineer. It was a while ago. I could understand that once the program starts my readings are no longer read. But I need to redesign or change that program in which both analog outputs continously varies with time both by amplitude and frequency while the program is running. I get some error messages like 50103  when i try to put all of them in a single while loop. Any suggestions please? I have PCI 6221 and Labview 8.2.1.

[Dennis_Knutson]

That error is resource reserved and indicates that you are trying to run more than one task of the same type at the same time. You cannot run more that one analog out task or more than one analog in task. Instead, you use a single task with multiple channels. There are shipping examples of the PID control kit and others that don't use the toolkit but have analog in and analog out in the same task. Yours would be similar except you would be using the Keithely instead of the analog in.

[MEMS]

Thanks for your reply. I was once told by a NI technical engineer that PCI 6221 can send analog outputs on both of its AO ports at the same time and we can program accordingly. He helped me in developing the second program which i have attached. Later on i realised that i have to change that program in which the amplitude of the signal varies with time or with respect to each reading from keithley. Is there a way that I can send two analog outputs at the same time varying the amplitude or its signal type while the program is running with respect to the feedback from the keithley.

Dinesh

[MEMS]

Hello Dennis

  I found an example which i have attached. I need some help in changing the design in which i can send signals to two analog outputs ao1and ao0 at the same time instead of only one. Can you help.

Dinesh

[Dennis_Knutson]

There is a shipping example called Cont Gen Voltage Wfm-Int Clk-Non Regeneration. I made the modification as below. See if that works for you.

[MEMS]

Hello  Dennis

         I did the same changes and it works. Thank you very much.

Dinesh