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???
05/08/06 17:17
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 		 #115809 - Negligible
Responding to: ???'s previous message
Prahlad said:
Once my instrument start measuring input signal the measurement can last max upto 2 seconds so I can measure Vref after finishing the desired signal measurement and then scale the result based on this AVref value. Is this approach ok. How much error can be caused when using this method?

Looks good! What I was refering to were the changes that can develop due to the drift after several hours, or even days... Two seconds are totally negligible.

Prahlad said:
How about using a 2.5V ref direcly connected to Vref pin of micro and change gain of input signal to match with this Vref of 2.5V?

Is also an option. But it's not wise to reduce Vref, and by this the ADC range, because this will always increase the susceptibility against noise, intereference, offset voltages and their drifts.

Kai

List of 42 messages in thread
TopicAuthorDate
Battery powered hand hel mixed signal            01/01/70 00:00      
   Be prepared to make a mistake            01/01/70 00:00      
      Re: Prepared to make a mistake            01/01/70 00:00      
         We're all learning            01/01/70 00:00      
   Some points...            01/01/70 00:00      
      Re: Some Points.            01/01/70 00:00      
         Answers            01/01/70 00:00      
            Re: Answers.            01/01/70 00:00      
               then...            01/01/70 00:00      
                  How much error can it cause.            01/01/70 00:00      
                     Negligible            01/01/70 00:00      
      10uH inductor + 100n            01/01/70 00:00      
         No big time delay is allowed            01/01/70 00:00      
   Modified as per suggestions.            01/01/70 00:00      
      No Cap At SV1.            01/01/70 00:00      
         Voltage drops?            01/01/70 00:00      
            Drop only 0.16V*2=0.32V            01/01/70 00:00      
               F+5V ?            01/01/70 00:00      
                  Re: F+5V & F-5V            01/01/70 00:00      
                     Good, that I aksed...            01/01/70 00:00      
                        Re: What else need changes            01/01/70 00:00      
                        why r7 to avcc.            01/01/70 00:00      
                           Ok            01/01/70 00:00      
                              Re: Capacitor with LM336            01/01/70 00:00      
                              You could do...            01/01/70 00:00      
                                 re: you could do.            01/01/70 00:00      
                                    What I meant            01/01/70 00:00      
                                       re: what i meant.            01/01/70 00:00      
                                          Present layout            01/01/70 00:00      
                                             Additionally...            01/01/70 00:00      
                              How do i connect protection diode to AVc            01/01/70 00:00      
                                 Like D3            01/01/70 00:00      
                                    Why do I need a diode.            01/01/70 00:00      
                                       credit for design            01/01/70 00:00      
                                          Thanks!            01/01/70 00:00      
                                       From ADC7-input to AVCC            01/01/70 00:00      
         Is needed            01/01/70 00:00      
            Re: Cap needed.            01/01/70 00:00      
   Modified final layouts.            01/01/70 00:00      
   I fixed your layout            01/01/70 00:00      
      Looks nice...            01/01/70 00:00      
   Design sent for PCB making            01/01/70 00:00      

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