Less than 1 hz triangle wave

[jjanas]

I'm creating a spring testing application that is basically ramping an actuator to a certain displacement and then back and is measuring force using a load cell.  I'm using the Simulate Signal express VI with a triangle wave with a given amplitude, frequency, and phase.  Everything works fine, except when I choose a frequency of less than 1 hz, it automatically outputs 1 hz.  Is it possible to output a triangle wave that is less than 1 hz?

Thanks.

Joe

Message Edited by jjanas on 12-01-2005 01:31 PM

[tbob]

I usually don't use express vi's so I'll give you an answer using standard vi's.  Use the Triangle Waveform vi found in functions palette - Waveform - Analog Waveform - Waveform Generation - Triangle Waveform.vi.  Set your input frequency to something less than 1 Hz.  Now you have to set the Sampling Info input.  Set Fs to 1000, and the #s (number of samples) will vary according to your frequency and the number of cycles you want to generate.  If your frequency is 0.1 Hz, you need 10,000 samples to get once complete cycle.  The general formula to get one cycle is 1/frequency * sample rate.  For 0.1 Hz, this is (1/0.1)*1000=10,000.  To get more than one cycle just multiply the answer by the number of cycels you want.  Formula is NumberOfCycles*(1/freq)*SampleRate.  See attached picture to see how to do this in Labview:

Message Edited by tbob on 12-01-2005 12:59 PM