Actually except power supply, the knife is used with some voltage modulated at 120 hz freq. How and where does the less than 25 hz noise come from variation of RF current? I am following Biomedical Signal Analysis by Rangaraj. It's written bovie is used at a frequency of 120 Hz. Then where from RF current of 25hz noise comes. This noise comes in electro-surgery and get added with ecg.
Hello friend,
Before identifying actual source, first consider if your grounding and shielding is done properly or not. This may reduce your problem considerably. Most stray pick-up problems are related to inadequate shielding or improper grounding of multiple systems.
I would guess you're seeing RF rectification at the inputs of your analog circuits. You can attenuate this by putting simple low-pass filters on the inputs. You should look at X2Y capacitors for this purpose as it is critical to match the inductances at RF frequencies. Shielding is also critical to reduce these effects.
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