is there a way to make the Arduino act as a voltage source, by generating sinusoidal, triangular and other kinds of signals? If so, can it be done using LabVIEW? (I've already managed reading analog signals using VISA)
The Due (and similar SAM based boards) have a DAC built in which can be set to different voltages (I forget the range off hand, maybe 0-Vcc at 12-bit resolution). Change that voltage fast enough, and you have a waveform.
Other Arduinos have PWM outputs which, when filtered through a low-pass filter, give a voltage proportional to the duty cycle of the PWM. Again, change the duty cycle fast enough and you have a waveform (limited by the carrier frequency of the PWM).
Can you do it from LabVIEW? Who knows? I have never used it.