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???
03/07/11 18:39
Modified:
  03/07/11 18:40
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 		 #181483 - Interesting...
Responding to: ???'s previous message
Aubrey said:
I found that on a 50 Hz signal in order to suppress a ripple, I needed a large smoothing capacitor which killed the response to several hundred mS if memory serves.

The usual workarround is to use a 2-pole Sallen-Key post filter. This allows you to minimize the averaging cap to the absolute minimum required by the operating principle. The 2-pole post filter tremendously reduces the ripple caused by the small averaging cap without sacrificing the settling time all too much.

I'm not familiar with the LTC1966, but I can only see an improvement in linearity but not an improvement in settling time and ripple. Tell me if I'm wrong...

Maybe Sonia can check out both and tell us her results?

Kai Klaas

List of 28 messages in thread
TopicAuthorDate
Adding a DC biac to a bipolar signal?            01/01/70 00:00      
   summing            01/01/70 00:00      
      Resitor bias            01/01/70 00:00      
         Yes, mentioned but maybe missed            01/01/70 00:00      
   What about the character of the signal?            01/01/70 00:00      
      Information content..            01/01/70 00:00      
         Hardly....            01/01/70 00:00      
            So the only option would be software RMS?            01/01/70 00:00      
               100Hz or 100 beats per minute?            01/01/70 00:00      
                  100Hz.            01/01/70 00:00      
                     50-150Hz is in the range of AD637!            01/01/70 00:00      
                        That's great! (but some other concerns...)            01/01/70 00:00      
                           Can you show us a typical signal?            01/01/70 00:00      
                              A Typical EMG Signal            01/01/70 00:00      
                                 Probably tough for rms chi            01/01/70 00:00      
                                    I'm working with a dsPIC            01/01/70 00:00      
                                       Shouldn't be too expensive            01/01/70 00:00      
                                 Give the AD637 a try...            01/01/70 00:00      
                                    Look at LTC1966            01/01/70 00:00      
                                       Interesting...            01/01/70 00:00      
                                          Just received a fresh new batch of AD637s            01/01/70 00:00      
               Negative supply voltage available?            01/01/70 00:00      
   Does your system have a driven electrode?            01/01/70 00:00      
   better be careful            01/01/70 00:00      
      Regrowth            01/01/70 00:00      
         are you suggesting that humans are expendable?            01/01/70 00:00      
            All precautions taken.            01/01/70 00:00      
            Obviously            01/01/70 00:00      

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