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???
04/10/06 15:11
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 		 #113971 - Only good for a few pF
Responding to: ???'s previous message
Aubrey said:
I tried searching and it seems to me no one mentioned a capacitance to digital converter. It seems there is a market for such things- see the Analog Devices AD7142 or AD7745 and there appear to be other devices in the range.

These chips only allow the determination of capacitances in the pf-range, but Prahlad is measuring 47nF caps.

Kai

List of 157 messages in thread
TopicAuthorDate
Measuring capacitance very precisely.            01/01/70 00:00      
   "I want the best money can buy, but I do            01/01/70 00:00      
      In this specific case I disagree.            01/01/70 00:00      
   Bridge?            01/01/70 00:00      
      Bridge!            01/01/70 00:00      
   AC bridge            01/01/70 00:00      
      Error Sources            01/01/70 00:00      
         Blumlein Bridge            01/01/70 00:00      
            Blumlein Bridre.            01/01/70 00:00      
               Bridge excitation            01/01/70 00:00      
            Blumlein            01/01/70 00:00      
   Let the statistics be your friend...            01/01/70 00:00      
      frequency meter            01/01/70 00:00      
      Product as a Transfer Standard            01/01/70 00:00      
         Distributor of your confidence            01/01/70 00:00      
            Suppliers like that ...            01/01/70 00:00      
               why blame the suppliers            01/01/70 00:00      
                  Not at all            01/01/70 00:00      
                  Hah!            01/01/70 00:00      
      Statistics for reference determination.            01/01/70 00:00      
         You got it!            01/01/70 00:00      
   questions            01/01/70 00:00      
      he wants to select to 0.1% from 1% stock            01/01/70 00:00      
         that is a bad idea            01/01/70 00:00      
            Hmm            01/01/70 00:00      
      That's a good way            01/01/70 00:00      
         posts cross timed            01/01/70 00:00      
            It makes sense to select them            01/01/70 00:00      
      No sorting of Caps.            01/01/70 00:00      
         then, are you not using the wrong approa            01/01/70 00:00      
            Time constant            01/01/70 00:00      
            Re: Eliminate cap sorting            01/01/70 00:00      
               Example            01/01/70 00:00      
               you do not need precision, you need rate            01/01/70 00:00      
         Would it not be easier the other way?            01/01/70 00:00      
            Difficult            01/01/70 00:00      
               Yes Digital Difficult.            01/01/70 00:00      
                  I think the point has been missed again.            01/01/70 00:00      
                     Demo ?            01/01/70 00:00      
                        Difficult to change now.            01/01/70 00:00      
                           Don't worry            01/01/70 00:00      
                              Re: Dont Worry.            01/01/70 00:00      
                                 How to calibrate an integrator?            01/01/70 00:00      
                                    Re: How to calib. an integratrator.            01/01/70 00:00      
                                       Answers            01/01/70 00:00      
                                    256Hz too fast.            01/01/70 00:00      
                                       Integrator and RMS using DSP            01/01/70 00:00      
                                          Whats available easily.            01/01/70 00:00      
                                             dsPIC30F2010            01/01/70 00:00      
                                                500 kSPS            01/01/70 00:00      
                                                   This little PICcy got eaten, the SILabs            01/01/70 00:00      
                                                      Is that useful?            01/01/70 00:00      
                                                         Planning to use dspic.            01/01/70 00:00      
                                                         Speed ?            01/01/70 00:00      
                                                            But for what purpose?            01/01/70 00:00      
                                                               MAC            01/01/70 00:00      
                                                                  it is amazing            01/01/70 00:00      
                                                                     Here is the analysis            01/01/70 00:00      
                                                                        the content, not the words            01/01/70 00:00      
                                                                           analysis please            01/01/70 00:00      
                                                                              since you, just like me, have no idea ab            01/01/70 00:00      
                                                                                 Ah! The Horatio quote version 2!            01/01/70 00:00      
                                                                                    again, you focus on words, not content            01/01/70 00:00      
                                                                                       Which is why I asked...            01/01/70 00:00      
                                                                                          If what you are saying is that I can not            01/01/70 00:00      
                                                                                          I had to.            01/01/70 00:00      
                                                                                             You said it!            01/01/70 00:00      
                                                                              Analog integrator            01/01/70 00:00      
                                       How do you calculate the RMS?            01/01/70 00:00      
                                          RMS in detail.            01/01/70 00:00      
                                          Out of interest.            01/01/70 00:00      
                                             wot you want a RMS demo,steve??            01/01/70 00:00      
                                                FIXED point            01/01/70 00:00      
                                                   fixed point is almost as bad            01/01/70 00:00      
                                       Alternative            01/01/70 00:00      
                                          NCO again            01/01/70 00:00      
                                             Would be nice            01/01/70 00:00      
                                                Timer2 of 89C52            01/01/70 00:00      
                                                   clever            01/01/70 00:00      
                                                      Oops! Incomplete statement            01/01/70 00:00      
                                                         Clock feedthrough            01/01/70 00:00      
                                                            Maxim App note            01/01/70 00:00      
                                                               Nice links, thanks!            01/01/70 00:00      
                                                               AD9832            01/01/70 00:00      
                                                            sine vawe            01/01/70 00:00      
                                          Re: Alternative.            01/01/70 00:00      
                                             Will work            01/01/70 00:00      
                                          Re: 64Hz Gain 1.126.            01/01/70 00:00      
                                             Maximum input voltage range            01/01/70 00:00      
                                                Re: Max. Input voltage Range.            01/01/70 00:00      
                                                   You have got it            01/01/70 00:00      
                                                      indeed, and            01/01/70 00:00      
                                                         Is the resistor in gnd really needed.            01/01/70 00:00      
                                                            Negligible with CMOS Opamps            01/01/70 00:00      
                                                               Re: Negligible with CMOS Opamps.            01/01/70 00:00      
                                                                  Most opamp datasheet do specify            01/01/70 00:00      
                                                                  Input Bias Current            01/01/70 00:00      
                                                                  Impedance matching            01/01/70 00:00      
                                                                     Re: Impedence Matching.            01/01/70 00:00      
                                                         yess balancing is required and to that..            01/01/70 00:00      
                                          4u7 Cap polarity and type.            01/01/70 00:00      
                                             Foil caps are needed            01/01/70 00:00      
                                                Available Capacitors.            01/01/70 00:00      
                                                   This one            01/01/70 00:00      
                                                      What are these MK equivalents            01/01/70 00:00      
                                                         MKT, MKP, MKC, KT, KP, KC,...            01/01/70 00:00      
                                                            Thanks Kai,            01/01/70 00:00      
                                          Ground Planes.            01/01/70 00:00      
                                             Have you had problems?            01/01/70 00:00      
                                                RE: Have you had problems.            01/01/70 00:00      
                                                   Keep the oscillator away from output            01/01/70 00:00      
                                                      Board Layouts.            01/01/70 00:00      
                                                         Recommendations            01/01/70 00:00      
                                                            Corrected Board            01/01/70 00:00      
                                                               I try to draw it for you            01/01/70 00:00      
                                                                  RE: I try to draw it.            01/01/70 00:00      
                                                                     Here it is            01/01/70 00:00      
                                                                        RE: Corrected Ver 2.0            01/01/70 00:00      
                                                                           Answers            01/01/70 00:00      
                                                                              Re: Corrected Ver. 3.0            01/01/70 00:00      
                                                                                 Some hints            01/01/70 00:00      
                                                                                    Re: I am in trouble.            01/01/70 00:00      
                                                                                       Sorry!            01/01/70 00:00      
                                                                                       Is this schematic correct.            01/01/70 00:00      
                                                                                          Corrections            01/01/70 00:00      
                                                                                             Re: Correction.            01/01/70 00:00      
                                                                                                Mylars will do            01/01/70 00:00      
                                                                                             Corrected Board and schematics Ver 4.0            01/01/70 00:00      
                                                                                                Why not doing it like this?            01/01/70 00:00      
                                                                                                   Re: Corrected boards ver 5.0            01/01/70 00:00      
                                                                                                      Some hints            01/01/70 00:00      
                                                                                                         Corrected board ver: 6.0            01/01/70 00:00      
                                                                                                            Please remove it...            01/01/70 00:00      
                                                                                                               Yes removed Gnd plane from mount hole.            01/01/70 00:00      
                                                                                                                  Looks good now            01/01/70 00:00      
                                                                                                                     Does than mean Green signal.            01/01/70 00:00      
                                                                                                                        Yes            01/01/70 00:00      
                                                                                                                           Thanks Kai.            01/01/70 00:00      
                                                                        trying to understand that            01/01/70 00:00      
                                                                           DC impedance of ground plane            01/01/70 00:00      
                                          bipolar swings how and where?            01/01/70 00:00      
                                             Here            01/01/70 00:00      
                                                explain a bit please            01/01/70 00:00      
                                                   Explaination            01/01/70 00:00      
                           Me ?            01/01/70 00:00      
                        Exactly!!            01/01/70 00:00      
   as requested a demo.....,sort of            01/01/70 00:00      
   simulation results of the demo...sort of            01/01/70 00:00      
      Thanks Jez.            01/01/70 00:00      
   Changing Q7 to Q9.            01/01/70 00:00      
   AD7142/AD7745            01/01/70 00:00      
      Only good for a few pF            01/01/70 00:00      
         My apologies            01/01/70 00:00      
            No need to apologize!            01/01/70 00:00      
         Nice part            01/01/70 00:00      
   Built Precision Sine Wave Generator.            01/01/70 00:00      
      Good luck            01/01/70 00:00      

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