Why Is My Oscilloscope Signal Pulsating?

[nordmoon]

Hi, so i am doing measurements with a pulsed laser using an oscilliscope.

The signal has been ok (stable) until this afternoon when I noticed the signal started pulsating. The baseline of the signal suddenly jumps up and the baseline becomes larger, and then go down to normal.. and it keeps "pulsating" like this. Any idea what could be wrong? There might be some disturbances from other work nearby, but I am unsure what it could be.

 

[berkeman]

Hi, so i am doing measurements with a pulsed laser using an oscilliscope.

The signal has been ok (stable) until this afternoon when I noticed the signal started pulsating. The baseline of the signal suddenly jumps up and the baseline becomes larger, and then go down to normal.. and it keeps "pulsating" like this. Any idea what could be wrong? There might be some disturbances from other work nearby, but I am unsure what it could be.

Could you use the UPLOAD button to post pictures of your setup and show us your schematic?

 

[Charles Link]

One thing to check would be the photodiode/amplifier. If you have a replacement, try testing with a different one.

 

[tech99]

It looks like interference from a nearby radio transmitter going on and off, such as a paging transmitter.

 

[nordmoon]

It looks like interference from a nearby radio transmitter going on and off, such as a paging transmitter.

I agree, when i removed the averaging I could see that there was a signal detected at some interval by the LPD3 tube.