25kHz PWM signal to analog voltage (DC) using low-pass filter: Weird output

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19

Hi bankaienator

I looked again at the photo you posted, and found the manual for the Agilent 33210A you are using:

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CE4QFjAC&url=http%3A%2F%2Fwww.physics.rutgers.edu%2Fugrad%2F326%2Fhp_33210a_User_guide.pdf&ei=QWR0U4DkCYSVPcrDgLgH&usg=AFQjCNFk4qHZ_42nyNDtZq8_dnB7skA6Pw&sig2=FKSnHgT6xxO8PmxoCr3E5A&bvm=bv.66699033,d.ZWU

The indication on the Agilent display is that your waveform is alternating about a 0V DC offset, which is the default for the Agilent.

Check out pages 20 and 21 of the manual for how to set the signal limits to 0V and +5V, and see if that helps.

Also, for testing, it looks like the square wave output from the Agilent can have its duty cycle varied easily. This might be a good place to start.

All the best

Ray