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???
02/22/12 10:03
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 		 #186131 - 2 i.c.s plus 6 R, C
Responding to: ???'s previous message
I am sure that the hardware circuit will work fine. It just seems a lot of parts !!

A diesel engine can't alter its revs instantaneously.
It is trivial to measure 10Hz .. 70Hz. You have the answer within one period (100ms .. 14ms).

Humans like to see a precise display. So it is worth averaging your period readings, and calculating the frequency from the 'smoothed' value.

All the same, if your revs change from 599 to 600 or more likely 1999RPM to 2000RPM to 1999RPM you get several digits changing.

Remember that your customer probably has no clue. You want to provide a 'pleasant' display. With software, you can smooth out these variations to any timescale or accuracy that you desire. Hardware involves soldering irons.

David.

List of 52 messages in thread
TopicAuthorDate
frequency multiplier x 10            01/01/70 00:00      
   You need some specs first.            01/01/70 00:00      
      and even more questions for your tutor            01/01/70 00:00      
   Analog solution...            01/01/70 00:00      
      Input wave form            01/01/70 00:00      
      Too Bad...            01/01/70 00:00      
   have you considered a "rate multiplier"?            01/01/70 00:00      
   PCA?            01/01/70 00:00      
      PCA Yes            01/01/70 00:00      
   Update            01/01/70 00:00      
      2 i.c.s plus 6 R, C            01/01/70 00:00      
      4046 / 7490            01/01/70 00:00      
      I put my bet in the digital solution            01/01/70 00:00      
         digital solution            01/01/70 00:00      
            MCU / CPLD            01/01/70 00:00      
            Simple digital solution...            01/01/70 00:00      
               Engine too fast            01/01/70 00:00      
                  it could be made simpler            01/01/70 00:00      
                     cute            01/01/70 00:00      
               OR            01/01/70 00:00      
   Frequency Multipiler            01/01/70 00:00      
      Motivation?            01/01/70 00:00      
         Motivation ?????????            01/01/70 00:00      
            Motives            01/01/70 00:00      
               OK            01/01/70 00:00      
                  motivation guess            01/01/70 00:00      
                     I had the same feeling...            01/01/70 00:00      
                        and if you looked at any of his previous posts ...            01/01/70 00:00      
   A number of thins concern me ...            01/01/70 00:00      
      answers            01/01/70 00:00      
      Boring...            01/01/70 00:00      
         And in this case...            01/01/70 00:00      
            Yes ... but ...            01/01/70 00:00      
               Making what you need, from what you can get..            01/01/70 00:00      
                  slogans            01/01/70 00:00      
                  Is that what the display needs?            01/01/70 00:00      
                     10-700 Hz is expected output frequency - not input frequency            01/01/70 00:00      
                        I did make one mistake            01/01/70 00:00      
                           old rpm analog (or digital) display is what they have            01/01/70 00:00      
                              bursts...            01/01/70 00:00      
                                 See LM2917 for ancient tacho examples            01/01/70 00:00      
   PLL            01/01/70 00:00      
   More detail?            01/01/70 00:00      
      Yes, more details, please...            01/01/70 00:00      
         Details            01/01/70 00:00      
            This can have to do ...            01/01/70 00:00      
               sharp edges            01/01/70 00:00      
                  Which phase-detector?            01/01/70 00:00      
               re: this can have            01/01/70 00:00      
                  What I would do...            01/01/70 00:00      
                     Very Low Frequency            01/01/70 00:00      
                        Give it a try...            01/01/70 00:00      

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