What are 6.5 Digit Multimeters Good For?
in [Design]
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From: John Larkin on 14 Mar 2010 21:53 On Sun, 14 Mar 2010 18:32:13 -0700, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >On Sun, 14 Mar 2010 00:36:08 GMT, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: > >>On a sunny day (Sat, 13 Mar 2010 08:13:20 -0600) it happened John Fields >><jfields(a)austininstruments.com> wrote in >><l37np519aum4a3r6n9aetaona9ij7hesm7(a)4ax.com>: >> >>>On Sat, 13 Mar 2010 13:27:35 GMT, Jan Panteltje >>><pNaonStpealmtje(a)yahoo.com> wrote: >>> >>>>On a sunny day (Fri, 12 Mar 2010 13:00:04 -0800) it happened D from BC >>>><myrealaddress(a)comic.com> wrote in <MPG.26044b27299d843e9896f7(a)209.197.12.12>: >>>> >>>>>In article <hne8fg$uqm$1(a)news.albasani.net>, pNaonStpealmtje(a)yahoo.com >>>>>says... >>>>>> >>>>>> On a sunny day (Fri, 12 Mar 2010 10:50:48 -0600) it happened John Fields >>>>>> <jfields(a)austininstruments.com> wrote in >>>>>> <ekrkp5lg8obtcmftn2tmq8adsnlte9u59e(a)4ax.com>: >>>>>> >>>>>> >On Fri, 12 Mar 2010 12:30:31 GMT, Jan Panteltje >>>>>> ><pNaonStpealmtje(a)yahoo.com> wrote: >>>>>> > >>>>>> >>On a sunny day (Thu, 11 Mar 2010 17:56:35 -0800) it happened D from BC >>>>>> >><myrealaddress(a)comic.com> wrote in <MPG.26033f321480b139896e5(a)209.197.12.12>: >>>>>> >> >>>>>> >>>6.5 digit multimeters sell around $1000.00. >>>>>> >>>For electronics development, are these $1000 multimeters really >>>>>> >>>necessary? >>>>>> >>>What are they good for? >>>>>> >> >>>>>> >>They are not needed, all you need is a 5 Euro multimeter, >>>>>> >>and in extreme cases a precise reference. >>>>>> >>That means if you use one of those reference chips, you borrow >>>>>> >>the very accurate multimeter for a day, measure your reference chip, >>>>>> >>write it down, and use that to calibrate your cheap multimeter, >>>>>> >>or o compute it's real value, >>>>>> >>Saved: 1000$ >>>>>> > >>>>>> >--- >>>>>> >If you don't _need_ the accurate multimeter, then how do you get around >>>>>> >the fact that unless you use _it_ to measure the reference, your cheap >>>>>> >multimeter is pretty much a boat anchor? >>>>>> > >>>>>> > >>>>>> >JF >>>>>> >>>>>> Sorry can you explain that again in electronics English? >>>>> >>>>>He means you still need an accurate tool to make use of a less accurate >>>>>tool. Which raises the question, why have the less accurate tool? >>>>> >>>>>btw... Boat anchor is a term I sometimes use for large heavy antiqued >>>>>test equipment. >>>>>Pre LCD scopes are boat anchors. >>>> >>>>Yes, OK, but Fields did not read very well, >>>>you only need the accurate one ONCE. >>>>And that means you can go to a place and have yor reference measured. >>> >>>--- >>>You seem to be the one having trouble with the language since even if >>>it's used only once, you still _need_ the higher accuracy instrument in >>>order to determine the error in the lower accuracy one. >>> >>>JF >> >>No you do not, how do you think those instruments came about? >>In your theory nothing could ever be made. >>:-) > >You are missing some concepts here. >There are things called reference cells, the voltage across the >terminals is dependant on the chemistry/physics. Similar to and >far lower tech to make than bandgap references. The terminal >voltage can be determined to 6 places before putting the meter >leads to them and are repeatable and reliable. >Ratiometric methods can maintain resolution and accuracy in a large >variety of situations, see R/2R DAC systems. >With these concepts in hand you would not have bothered to make your >comment. >Or maybe you do not credit anyone else with these few bits of >typical electrical engineering knowledge. Do people still use standard cells? John
From: Jim Yanik on 14 Mar 2010 21:56 Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in news:041rp554feflu3181c1csiov3v4in58ubo(a)4ax.com: > On Sun, 14 Mar 2010 18:46:36 -0700, > "JosephKK"<quiettechblue(a)yahoo.com> wrote: > >>On Fri, 12 Mar 2010 10:44:39 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >> >>>On Fri, 12 Mar 2010 09:33:25 -0800, D from BC >>><myrealaddress(a)comic.com> wrote: >>> >>>>In article <hndc5b$37k$1(a)news.albasani.net>, >>>>pNaonStpealmtje(a)yahoo.com says... >>>>> >>>>> On a sunny day (Thu, 11 Mar 2010 17:56:35 -0800) it happened D >>>>> from BC <myrealaddress(a)comic.com> wrote in >>>>> <MPG.26033f321480b139896e5(a)209.197.12.12>: >>>>> >>>>> >6.5 digit multimeters sell around $1000.00. >>>>> >For electronics development, are these $1000 multimeters really >>>>> >necessary? >>>>> >What are they good for? >>>>> >>>>> They are not needed, all you need is a 5 Euro multimeter, >>>>> and in extreme cases a precise reference. >>>>> That means if you use one of those reference chips, you borrow >>>>> the very accurate multimeter for a day, measure your reference >>>>> chip, write it down, and use that to calibrate your cheap >>>>> multimeter, or o compute it's real value, >>>>> Saved: 1000$ >>>>> >>>>> Of course there are exceptions, >>>>> but in places where that counts they usually have a lot of >>>>> ++++expensive stuff anyways. Usually places where nothing really >>>>> useful is done, like in CERN, or ITER, or LIGO, etc. >>>> >>>>How about mohm measurements? Maybe that's handy. >>>>My DMM only goes to 0.1 ohm. >>>>I thought of measuring DCR of coils or pcb trace resistance for sim >>>>accuracy. >>>> >>>> >>> >>>Measuring milli-Ohms is tricky. Ideally you'd like 4-point-probe >>>measuring... voltage "viewing" pins are separate from current forcing >>>pins. >>> >>>I'd do it with an AC current source, so you can gain-up the resulting >>>voltage. >>> >>> ...Jim Thompson >> >>So, you know some interesting tricks to make an AC current source >>accurate to 0.01%? A lot of people would interested, especially if >>it was a clean sine source. With a good clean DC current source i >>have seen measurements all the way to 0.00002%. There be tradeoffs >>here. > > Why do need "accuracy" to 0.01%? What are you trying to measure to > that kind of accuracy? > > ...Jim Thompson Calibration source. You want at least 4x better accuracy than the DUT. but he was referring to millohm measurements using a Kelvin connection. -- Jim Yanik jyanik at localnet dot com
From: Jim Thompson on 14 Mar 2010 22:10 On Sun, 14 Mar 2010 20:56:44 -0500, Jim Yanik <jyanik(a)abuse.gov> wrote: >Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in >news:041rp554feflu3181c1csiov3v4in58ubo(a)4ax.com: > >> On Sun, 14 Mar 2010 18:46:36 -0700, >> "JosephKK"<quiettechblue(a)yahoo.com> wrote: >> >>>On Fri, 12 Mar 2010 10:44:39 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >>> >>>>On Fri, 12 Mar 2010 09:33:25 -0800, D from BC >>>><myrealaddress(a)comic.com> wrote: >>>> >>>>>In article <hndc5b$37k$1(a)news.albasani.net>, >>>>>pNaonStpealmtje(a)yahoo.com says... >>>>>> >>>>>> On a sunny day (Thu, 11 Mar 2010 17:56:35 -0800) it happened D >>>>>> from BC <myrealaddress(a)comic.com> wrote in >>>>>> <MPG.26033f321480b139896e5(a)209.197.12.12>: >>>>>> >>>>>> >6.5 digit multimeters sell around $1000.00. >>>>>> >For electronics development, are these $1000 multimeters really >>>>>> >necessary? >>>>>> >What are they good for? >>>>>> >>>>>> They are not needed, all you need is a 5 Euro multimeter, >>>>>> and in extreme cases a precise reference. >>>>>> That means if you use one of those reference chips, you borrow >>>>>> the very accurate multimeter for a day, measure your reference >>>>>> chip, write it down, and use that to calibrate your cheap >>>>>> multimeter, or o compute it's real value, >>>>>> Saved: 1000$ >>>>>> >>>>>> Of course there are exceptions, >>>>>> but in places where that counts they usually have a lot of >>>>>> ++++expensive stuff anyways. Usually places where nothing really >>>>>> useful is done, like in CERN, or ITER, or LIGO, etc. >>>>> >>>>>How about mohm measurements? Maybe that's handy. >>>>>My DMM only goes to 0.1 ohm. >>>>>I thought of measuring DCR of coils or pcb trace resistance for sim >>>>>accuracy. >>>>> >>>>> >>>> >>>>Measuring milli-Ohms is tricky. Ideally you'd like 4-point-probe >>>>measuring... voltage "viewing" pins are separate from current forcing >>>>pins. >>>> >>>>I'd do it with an AC current source, so you can gain-up the resulting >>>>voltage. >>>> >>>> ...Jim Thompson >>> >>>So, you know some interesting tricks to make an AC current source >>>accurate to 0.01%? A lot of people would interested, especially if >>>it was a clean sine source. With a good clean DC current source i >>>have seen measurements all the way to 0.00002%. There be tradeoffs >>>here. >> >> Why do need "accuracy" to 0.01%? What are you trying to measure to >> that kind of accuracy? >> >> ...Jim Thompson > >Calibration source. You want at least 4x better accuracy than the DUT. > > >but he was referring to millohm measurements using a Kelvin connection. I think people with three place data and churning it to "accuracies" of 4 or 6 places are nuts equivalent to climate change scientists :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Archimedes' Lever on 15 Mar 2010 00:15 On Sun, 14 Mar 2010 19:10:00 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >On Sun, 14 Mar 2010 20:56:44 -0500, Jim Yanik <jyanik(a)abuse.gov> >wrote: > >>Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in >>news:041rp554feflu3181c1csiov3v4in58ubo(a)4ax.com: >> >>> On Sun, 14 Mar 2010 18:46:36 -0700, >>> "JosephKK"<quiettechblue(a)yahoo.com> wrote: >>> >>>>On Fri, 12 Mar 2010 10:44:39 -0700, Jim Thompson >>>><To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >>>> >>>>>On Fri, 12 Mar 2010 09:33:25 -0800, D from BC >>>>><myrealaddress(a)comic.com> wrote: >>>>> >>>>>>In article <hndc5b$37k$1(a)news.albasani.net>, >>>>>>pNaonStpealmtje(a)yahoo.com says... >>>>>>> >>>>>>> On a sunny day (Thu, 11 Mar 2010 17:56:35 -0800) it happened D >>>>>>> from BC <myrealaddress(a)comic.com> wrote in >>>>>>> <MPG.26033f321480b139896e5(a)209.197.12.12>: >>>>>>> >>>>>>> >6.5 digit multimeters sell around $1000.00. >>>>>>> >For electronics development, are these $1000 multimeters really >>>>>>> >necessary? >>>>>>> >What are they good for? >>>>>>> >>>>>>> They are not needed, all you need is a 5 Euro multimeter, >>>>>>> and in extreme cases a precise reference. >>>>>>> That means if you use one of those reference chips, you borrow >>>>>>> the very accurate multimeter for a day, measure your reference >>>>>>> chip, write it down, and use that to calibrate your cheap >>>>>>> multimeter, or o compute it's real value, >>>>>>> Saved: 1000$ >>>>>>> >>>>>>> Of course there are exceptions, >>>>>>> but in places where that counts they usually have a lot of >>>>>>> ++++expensive stuff anyways. Usually places where nothing really >>>>>>> useful is done, like in CERN, or ITER, or LIGO, etc. >>>>>> >>>>>>How about mohm measurements? Maybe that's handy. >>>>>>My DMM only goes to 0.1 ohm. >>>>>>I thought of measuring DCR of coils or pcb trace resistance for sim >>>>>>accuracy. >>>>>> >>>>>> >>>>> >>>>>Measuring milli-Ohms is tricky. Ideally you'd like 4-point-probe >>>>>measuring... voltage "viewing" pins are separate from current forcing >>>>>pins. >>>>> >>>>>I'd do it with an AC current source, so you can gain-up the resulting >>>>>voltage. >>>>> >>>>> ...Jim Thompson >>>> >>>>So, you know some interesting tricks to make an AC current source >>>>accurate to 0.01%? A lot of people would interested, especially if >>>>it was a clean sine source. With a good clean DC current source i >>>>have seen measurements all the way to 0.00002%. There be tradeoffs >>>>here. >>> >>> Why do need "accuracy" to 0.01%? What are you trying to measure to >>> that kind of accuracy? >>> >>> ...Jim Thompson >> >>Calibration source. You want at least 4x better accuracy than the DUT. >> >> >>but he was referring to millohm measurements using a Kelvin connection. > >I think people with three place data and churning it to "accuracies" >of 4 or 6 places are nuts equivalent to climate change scientists :-) > > ...Jim Thompson We got calculators and computers with big registers and mantissas these days. Keep all the accuracy possible along the entire observation chain, and do the rounding off at the end.
From: Martin Brown on 15 Mar 2010 04:20
D from BC wrote: > Neato :) They last about 25-30 years with the odd bit of refurbishment. A 7 DVM model still in use today (probably one of the last manufactured that way) is in the images online at Southampton university. http://www.noc.soton.ac.uk/isotope/Tims.htm Regards, Martin Brown |