I am working with spectral analyzer, it was setup recently but getting 60hz harmonics. for eliminating them I placed shield around the device and grounded even also I had the same problem. Please, suggest me the procedures to follow.
Thanks in advance
As you know this is caused by the power line. I am guessing the spectral analyzer device that you are using has some internal "notch" filter at the same frequecy to eliminate the harmonics.
If you're monitoring a device which function is to control energy with a 60 Hz fundamental frequency and it also has harmonic content, you will always be seeing the first harmonic in the spectral analyzer.
Surya,
-Sanjay
60 Hz EM interference is hard to suppress...
If your DUT (Device Under Test) is powered from the grid by means of some power supply, it may help to have the case ground of this power supply isolated vs. earth. The same measure can be applied to the spectrum analyzer. This can be achieved by using fully isolated transformers.
But be aware that the case of both devices may carry a voltage somewhere around the middle of the AC supply if the devices have an input EMI filter. In such cases it may help to connect the cases of the devices - still keeping them isolated from earth.
Hello Surya,
It is a normal and common experience that you see the typical power-line (50 or 60Hz) . Offcourse the power supply of the spectrum analyzer might and must have suitable filter, it is the pick-up by the DUT (as Dreher has stated) that appears to be a stronger signal input that your other signals.
Only shielding might improve your powerline interference problem but may not be totally eliminated. Think of solutions like Faraday-Cage, not like a big test-room but a small case to enclose your experimental setup with proper grounding.
I hope this works for you!
Best wishes and luck!
-PRASANNA WAICHAL
I can only confirm what has been already posted. Have a special attention for ground loops (i.e. grounding via different paths), try to have a single grounding point and make sure that all metallic parts (enclosures, plates...) are grounded. Check also if your devices have mechanical ground separate from electrical ground (could be source of ground loops). Hope that helps.
U. Dreher is correct - its a grounding issue. The ADC case and the device under test must have a common ground.
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