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generate low frequency square signal via analog output

hello all
i am new at labview and DAQ devices. i am working on project where using an electro-hydraulic servo system. i want to control the position of the hydraulic cylinder by means of controlling proportional hydraulic valve.i need to control the cylinder to extend and retract continuously. to do that, i need to give command signal (voltage) to the proportional valve with pattern like the attached picture, actually it is similar to PWM signal.

i am using Labview connected with NI-USB 6251. how to generate signal with pattern like the attached picture? i am trying to use Square signal on Simulate signal express VI, but when i set to the low frequency ( 0.1 Hz) , i got error message that "the buffer size is too small". im trying to change the buffer size but error still happened.  i can generate it via counter output, but i need to generate it via analog output.

thanks for your help guys.

 

PWM.JPG

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How about using Counter Output?

 

 

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GCentral
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desduen wrote: i am trying to use Square signal on Simulate signal express VI, but when i set to the low frequency ( 0.1 Hz) , i got error message that "the buffer size is too small". im trying to change the buffer size but error still happened.

Lower your sample rate.  With this low of an output frequency, 100S/s should be plenty.  Alternatively, use the Square Waveform.vi.


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thanks guys for your help.

i am trying to imply solution from 

 

pwm ask.jpg

 

it seems well on waveform chart, but when i try to connect NI-USB 6251 with oscilloscope to see the generated signal, i got the signal generated at constant 7 Volt. it never goes to 0 Volt. i wonder where is the mistake?

i set the DAQ Assistant as pict below :

pwm ask2.jpg

thanks for your help

 

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