Hi guys,
I'm currently developing a receiving device that picks up a specific frequency in your body. A metal strap is used as a pickup, which is in close proximity to the wearers skin. The pickup is connected to an amplifier and a little extra circuitry which detects the presence of the signal. This is also close to the wearers skin. The problem is that the amplifier and extra bits are picking up the signals in the body as much as the pickup is - this is causing common mode signals to appear and hence the device does not detect any signal.
It seems obvious that I need to shield the device for this to work. I need an electrically quiet area from which I can use a reference point, then the only place that the signal can get though is the pickup (as intended). My initial thought was that I would only need to shield the input amplifier but on second thoughts I may need to shield everything - any clarification on what I need to be shielding would be much appreciated.
I also do not know how to properly shield the device. If I put it all in a copper box, where do I connect the copper box to? If I connect it to "ground" (battery negative), then does that not mean all the signal the shield picks up gets put directly into the ground plane? If this is the case, do I leave the shield floating?
As I said I have never had to shield a floating battery operated device before so any pointers, references, criticisms etc. are all very welcome.
Thanks,
Dan
I'm currently developing a receiving device that picks up a specific frequency in your body. A metal strap is used as a pickup, which is in close proximity to the wearers skin. The pickup is connected to an amplifier and a little extra circuitry which detects the presence of the signal. This is also close to the wearers skin. The problem is that the amplifier and extra bits are picking up the signals in the body as much as the pickup is - this is causing common mode signals to appear and hence the device does not detect any signal.
It seems obvious that I need to shield the device for this to work. I need an electrically quiet area from which I can use a reference point, then the only place that the signal can get though is the pickup (as intended). My initial thought was that I would only need to shield the input amplifier but on second thoughts I may need to shield everything - any clarification on what I need to be shielding would be much appreciated.
I also do not know how to properly shield the device. If I put it all in a copper box, where do I connect the copper box to? If I connect it to "ground" (battery negative), then does that not mean all the signal the shield picks up gets put directly into the ground plane? If this is the case, do I leave the shield floating?
As I said I have never had to shield a floating battery operated device before so any pointers, references, criticisms etc. are all very welcome.
Thanks,
Dan
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