Hi,
I'm trying to measure a sinusoidal signal which is having an amplitue of 2 V and variant frequencies between 10 Hz ~ 300 Hz. I've tried "PRESET DIG" configuration and I was unable to get a waveform similar to sine wave. Then I tried "PRESET DIG" configuration again and then send "TIMER 0.01" command and frequency of the signal is 10 Hz. As far as I understood from the statements in user's guide, by sending "TIMER 0.01" command, I expect sampling rate to be 100 Hz. In this case, I expect to have at least one cycle of 10 Hz sine wave but I don't have it and I can't see at which part I'm wrong.
I've attached a screenshot of a portion of the graph I have. Any help will be appreciated.
Thanks in advance,
Emre
Hi,
It's normal to have this waveform, you have 10 samples per 10Hz cycle. On first the picture below, 10.162Hz sampling at 100 Hz (jumps of about 36 degrees per sample point), similar to your picture. I've done that in Excel. If you want more fidelity on the sinusoidal signal form, it will need more points. The other three images that follow, show with a sampling of 1000Hz. Now you see what to do at 300 Hz if you want to keep this precision, sampling rate should be 30kHz (result similar to second picture) and with input signal at 10 Hz, the last picture.
I do not know your application exactly, but if it's just the maximum value you're looking for, even if the shape is not perfectly sinuoidal, keep the maximum value in the samples received. The problem is to make sure that the actual maximum value will be in the samples. If you know what frequency to test, you could choose a lower sampling rate and you could be sure to find the peak value.
Yves