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Kai Klaas
02/15/06 07:42
Read: 1102 times
Germany


 
#110054 - You got it!
Responding to: Prahlad J. Purohit's previous message
Prahlad said:
These are MKP1837 type Vishay make 47nF precision metalised polypropelene capacitors with max manufacturing intial tolerance of 1% and aging drift <0.5% in 2 years.

I know them, they are brilliant! I have used 330nF types in a three way active loudspeaker box with fourth order Linkwitz-Riley filters.

You can improve your design, though, by using KP1836, if you need 47nF types. They show even better performance.

Prahlad said:
But due to againg effect I will need to choose new master atleast twice a year. Am I right?

This highly depends on flowing current and heat. So, if you have them in a box and store them in a cold and dry (!) room, then long term drift is even much lower.
Take care, that no condensing water is in the box!!! High humidity can influence capacitance. Put a sicca bag into the box, to keep moisture out.

Prahlad said:
And efforts are made to keep the process centered between UCL and LCL ie at 47nF thus the peak of bell distribution curve should ideally be at 47nF but processes rarely stay centered they tend to shift from center ie. peak of curve would deviate from 47nF in that case the statistical analysis from single lot may give slight error leading to error in value of reference cap. But again if samples from diffrent batches and diffrent sources are taken than this error will disappear. Am I right Kai?

Totally right!
If you take caps from same lot, you will notice, that errors between the individual caps is much smaller than +-1%. You will notice for instance, that all the caps don't differ by more than +-0.2%, but the average value of them being at let's say +0.4%. In a few hours same production line will show an error of average value of let's say -0.3%, but again with all the samples not differing by more than +-0.2%.
That's the reason why you should not use components sitting on the same strap. (Is 'strap' the right word?)
You can solve the problem also, if you buy these caps from same manufacturer but at different times. So, to be precisely, you do not need many caps, but many lots!

Prahlad said:
Bur unfortunately I have only one supplier availbale so I will try to collect samples from 10 diffrent batches atleast 5 samples.

Exactly!

Prahlad said:
Great method and probably the simplest too.

Remember, statistics has to do with infinite large numbers of samples. This nethode is only as good as statistically distributed your sampes are. So, try to get samples which fill the whole +-1% band.

Kai

List of 157 messages in thread
TopicAuthorDate
Measuring capacitance very precisely.      Prahlad J. Purohit      02/13/06 09:06      
   "I want the best money can buy, but I do      Erik Malund      02/13/06 09:24      
      In this specific case I disagree.      Kalpak Dabir      02/13/06 11:22      
   Bridge?      Andy Neil      02/13/06 09:31      
      Bridge!      Oliver Sedlacek      02/13/06 09:58      
   AC bridge      Steve M. Taylor      02/13/06 14:19      
      Error Sources      Bruce Bailey      02/13/06 15:04      
         Blumlein Bridge        Steve M. Taylor      02/13/06 16:59      
            Blumlein Bridre.      Prahlad J. Purohit      02/14/06 22:11      
               Bridge excitation      Oliver Sedlacek      02/15/06 03:18      
            Blumlein      Ian Bell      02/16/06 03:21      
   Let the statistics be your friend...        Kai Klaas      02/13/06 19:19      
      frequency meter      Christian Kleiber      02/14/06 07:30      
      Product as a Transfer Standard      Bruce Bailey      02/14/06 09:31      
         Distributor of your confidence      Kai Klaas      02/22/06 07:17      
            Suppliers like that ...      Bruce Bailey      02/22/06 07:58      
               why blame the suppliers      Erik Malund      02/22/06 08:06      
                  Not at all      Kai Klaas      02/22/06 10:08      
                  Hah!      Bruce Bailey      02/22/06 10:28      
      Statistics for reference determination.      Prahlad J. Purohit      02/15/06 00:02      
         You got it!      Kai Klaas      02/15/06 07:42      
   questions      Erik Malund      02/15/06 06:24      
      he wants to select to 0.1% from 1% stock      Terry Lingle      02/15/06 07:13      
         that is a bad idea      Erik Malund      02/15/06 07:54      
            Hmm      Kai Klaas      02/15/06 08:10      
      That's a good way      Kai Klaas      02/15/06 07:48      
         posts cross timed      Erik Malund      02/15/06 08:04      
            It makes sense to select them      Kai Klaas      02/15/06 08:18      
      No sorting of Caps.      Prahlad J. Purohit      02/15/06 08:16      
         then, are you not using the wrong approa      Erik Malund      02/15/06 09:27      
            Time constant      Kai Klaas      02/15/06 10:16      
            Re: Eliminate cap sorting      Prahlad J. Purohit      02/15/06 22:06      
               Example      Steve M. Taylor      02/16/06 02:57      
               you do not need precision, you need rate      Erik Malund      02/16/06 06:36      
         Would it not be easier the other way?      Kalpak Dabir      02/15/06 10:35      
            Difficult      Kai Klaas      02/15/06 11:45      
               Yes Digital Difficult.      Prahlad J. Purohit      02/15/06 21:58      
                  I think the point has been missed again.      Jez Smith      02/16/06 07:54      
                     Demo ?      Steve M. Taylor      02/16/06 09:28      
                        Difficult to change now.      Prahlad J. Purohit      02/16/06 09:48      
                           Don't worry      Kai Klaas      02/16/06 09:59      
                              Re: Dont Worry.      Prahlad J. Purohit      02/17/06 08:07      
                                 How to calibrate an integrator?        Kai Klaas      02/19/06 13:29      
                                    Re: How to calib. an integratrator.      Prahlad J. Purohit      02/19/06 21:59      
                                       Answers      Kai Klaas      02/20/06 06:33      
                                    256Hz too fast.      Prahlad J. Purohit      02/20/06 02:51      
                                       Integrator and RMS using DSP      Kalpak Dabir      02/20/06 03:17      
                                          Whats available easily.      Prahlad J. Purohit      02/20/06 09:38      
                                             dsPIC30F2010      Kalpak Dabir      02/20/06 09:49      
                                                500 kSPS      Mahmood Elnasser      03/16/06 09:43      
                                                   This little PICcy got eaten, the SILabs      Erik Malund      03/16/06 10:33      
                                                      Is that useful?      Kalpak Dabir      03/19/06 07:09      
                                                         Planning to use dspic.      Prahlad J. Purohit      03/19/06 07:35      
                                                         Speed ?      Steve M. Taylor      03/19/06 07:55      
                                                            But for what purpose?      Kalpak Dabir      03/19/06 11:36      
                                                               MAC      Steve M. Taylor      03/19/06 12:16      
                                                                  it is amazing      Erik Malund      03/20/06 07:41      
                                                                     Here is the analysis      Kalpak Dabir      03/20/06 09:36      
                                                                        the content, not the words      Erik Malund      03/20/06 10:54      
                                                                           analysis please      Kalpak Dabir      03/20/06 11:38      
                                                                              since you, just like me, have no idea ab      Erik Malund      03/20/06 13:12      
                                                                                 Ah! The Horatio quote version 2!      Kalpak Dabir      03/20/06 19:30      
                                                                                    again, you focus on words, not content      Erik Malund      03/21/06 06:45      
                                                                                       Which is why I asked...      Kalpak Dabir      03/21/06 11:34      
                                                                                          If what you are saying is that I can not      Erik Malund      03/21/06 12:29      
                                                                                          I had to.      Steve M. Taylor      03/21/06 13:52      
                                                                                             You said it!      Kalpak Dabir      03/22/06 00:07      
                                                                              Analog integrator      Kai Klaas      03/20/06 18:48      
                                       How do you calculate the RMS?      Kai Klaas      02/20/06 06:48      
                                          RMS in detail.      Prahlad J. Purohit      02/20/06 09:35      
                                          Out of interest.      Steve M. Taylor      02/20/06 11:53      
                                             wot you want a RMS demo,steve??      Jez Smith      02/21/06 04:52      
                                                FIXED point      Steve M. Taylor      02/21/06 11:13      
                                                   fixed point is almost as bad      Jez Smith      02/21/06 14:16      
                                       Alternative        Kai Klaas      02/20/06 13:30      
                                          NCO again      Steve M. Taylor      02/20/06 16:17      
                                             Would be nice      Kai Klaas      02/22/06 06:45      
                                                Timer2 of 89C52      Kalpak Dabir      02/22/06 06:58      
                                                   clever      Steve M. Taylor      02/22/06 08:38      
                                                      Oops! Incomplete statement      Kalpak Dabir      02/22/06 10:11      
                                                         Clock feedthrough      Kai Klaas      02/22/06 10:38      
                                                            Maxim App note        Steve M. Taylor      02/22/06 10:51      
                                                               Nice links, thanks!      Kai Klaas      02/22/06 10:54      
                                                               AD9832      Steve M. Taylor      02/22/06 14:13      
                                                            sine vawe      Erik Malund      02/24/06 11:35      
                                          Re: Alternative.      Prahlad J. Purohit      02/20/06 22:34      
                                             Will work      Kai Klaas      02/21/06 05:49      
                                          Re: 64Hz Gain 1.126.      Prahlad J. Purohit      02/21/06 03:41      
                                             Maximum input voltage range      Kai Klaas      02/21/06 06:17      
                                                Re: Max. Input voltage Range.      Prahlad J. Purohit      02/22/06 04:58      
                                                   You have got it      Kai Klaas      02/22/06 06:44      
                                                      indeed, and      Erik Malund      02/22/06 07:44      
                                                         Is the resistor in gnd really needed.      Prahlad J. Purohit      02/22/06 08:11      
                                                            Negligible with CMOS Opamps      Kai Klaas      02/22/06 09:16      
                                                               Re: Negligible with CMOS Opamps.      Prahlad J. Purohit      02/24/06 03:08      
                                                                  Most opamp datasheet do specify      Kalpak Dabir      02/24/06 07:53      
                                                                  Input Bias Current      Steve M. Taylor      02/24/06 09:55      
                                                                  Impedance matching      Kai Klaas      02/24/06 20:00      
                                                                     Re: Impedence Matching.      Prahlad J. Purohit      02/24/06 21:33      
                                                         yess balancing is required and to that..      Abhishek Singh      02/22/06 19:09      
                                          4u7 Cap polarity and type.      Prahlad J. Purohit      02/23/06 03:57      
                                             Foil caps are needed      Kai Klaas      02/23/06 06:04      
                                                Available Capacitors.      Prahlad J. Purohit      03/07/06 01:31      
                                                   This one      Kai Klaas      03/07/06 07:39      
                                                      What are these MK equivalents      Prahlad J. Purohit      03/07/06 07:51      
                                                         MKT, MKP, MKC, KT, KP, KC,...      Kai Klaas      03/07/06 20:14      
                                                            Thanks Kai,      Prahlad J. Purohit      03/08/06 06:17      
                                          Ground Planes.      Prahlad J. Purohit      03/09/06 08:11      
                                             Have you had problems?      Kai Klaas      03/09/06 08:16      
                                                RE: Have you had problems.      Prahlad J. Purohit      03/09/06 08:19      
                                                   Keep the oscillator away from output      Kai Klaas      03/09/06 08:52      
                                                      Board Layouts.      Prahlad J. Purohit      03/09/06 09:53      
                                                         Recommendations      Kai Klaas      03/09/06 17:55      
                                                            Corrected Board      Prahlad J. Purohit      03/10/06 01:59      
                                                               I try to draw it for you      Kai Klaas      03/10/06 06:40      
                                                                  RE: I try to draw it.      Prahlad J. Purohit      03/11/06 08:28      
                                                                     Here it is        Kai Klaas      03/11/06 08:49      
                                                                        RE: Corrected Ver 2.0      Prahlad J. Purohit      03/12/06 01:44      
                                                                           Answers      Kai Klaas      03/13/06 06:51      
                                                                              Re: Corrected Ver. 3.0      Prahlad J. Purohit      03/14/06 03:30      
                                                                                 Some hints      Kai Klaas      03/16/06 09:02      
                                                                                    Re: I am in trouble.      Prahlad J. Purohit      03/16/06 09:35      
                                                                                       Sorry!      Kai Klaas      03/16/06 09:44      
                                                                                       Is this schematic correct.      Prahlad J. Purohit      03/16/06 09:45      
                                                                                          Corrections      Kai Klaas      03/16/06 10:04      
                                                                                             Re: Correction.      Prahlad J. Purohit      03/16/06 10:17      
                                                                                                Mylars will do      Kai Klaas      03/16/06 18:49      
                                                                                             Corrected Board and schematics Ver 4.0      Prahlad J. Purohit      03/19/06 01:44      
                                                                                                Why not doing it like this?      Kai Klaas      03/19/06 19:47      
                                                                                                   Re: Corrected boards ver 5.0      Prahlad J. Purohit      03/20/06 03:43      
                                                                                                      Some hints      Kai Klaas      03/20/06 11:50      
                                                                                                         Corrected board ver: 6.0      Prahlad J. Purohit      03/21/06 07:29      
                                                                                                            Please remove it...      Kai Klaas      03/21/06 07:49      
                                                                                                               Yes removed Gnd plane from mount hole.      Prahlad J. Purohit      03/21/06 08:00      
                                                                                                                  Looks good now      Kai Klaas      03/21/06 08:15      
                                                                                                                     Does than mean Green signal.      Prahlad J. Purohit      03/21/06 08:16      
                                                                                                                        Yes      Kai Klaas      03/21/06 08:41      
                                                                                                                           Thanks Kai.      Prahlad J. Purohit      03/21/06 19:44      
                                                                        trying to understand that      Abhishek Singh      03/13/06 21:52      
                                                                           DC impedance of ground plane      Kai Klaas      03/16/06 09:35      
                                          bipolar swings how and where?      Abhishek Singh      03/09/06 09:27      
                                             Here      Kai Klaas      03/09/06 09:30      
                                                explain a bit please      Abhishek Singh      03/09/06 10:19      
                                                   Explaination      Kai Klaas      03/09/06 10:55      
                           Me ?      Steve M. Taylor      02/16/06 10:20      
                        Exactly!!      Kai Klaas      02/16/06 09:57      
   as requested a demo.....,sort of      Jez Smith      02/16/06 13:47      
   simulation results of the demo...sort of      Jez Smith      02/16/06 23:53      
      Thanks Jez.      Prahlad J. Purohit      02/17/06 08:01      
   Changing Q7 to Q9.      Prahlad J. Purohit      03/16/06 10:23      
   AD7142/AD7745      Aubrey Kagan      04/10/06 07:26      
      Only good for a few pF      Kai Klaas      04/10/06 09:11      
         My apologies      Aubrey Kagan      04/10/06 09:26      
            No need to apologize!      Kai Klaas      04/10/06 10:43      
         Nice part      Steve M. Taylor      04/10/06 13:23      
   Built Precision Sine Wave Generator.      Prahlad J. Purohit      04/11/06 08:38      
      Good luck      Kai Klaas      04/11/06 09:10      

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