What are 6.5 Digit Multimeters Good For?
in [Design]
|
From: BarnCat on 12 Mar 2010 22:34 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. > > You do not need to measure. Just model the conductor runs by length and use them as resistive elements of the sim circuit. No need to measure what can easily be calculated to fairly extreme accuracy.
From: BarnCat on 12 Mar 2010 22:36 On Fri, 12 Mar 2010 16:36:25 -0500, Spehro Pefhany <speffSNIP(a)interlogDOTyou.knowwhat> wrote: >On Fri, 12 Mar 2010 12:43:08 -0800, D from BC ><myrealaddress(a)comic.com> wrote: > >>In article <hne7cu$st1$1(a)news.albasani.net>, pNaonStpealmtje(a)yahoo.com >>says... >>> >> >>> I have a controlled current souce. >>> Stuff 1 A through the .1 resistor and measure the voltage drop? >> >>Huh..My power supply does have constant I mode.. I'll try that someday. > >Be careful using power supplies that way. It's more intended as a >current limit than as a constant current supply. For one thing, it's >not very stable. Looks like you get the smarts award for today. It cannot be a mere current limit watchdog circuit. A constant current supply is a different animal.
From: Joel Koltner on 12 Mar 2010 23:11 "John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:1d3mp55bbhshdo7da63ifht2rdh5q2j4iu(a)4ax.com... > I have an Agilent 34401A, in the same class as the Keithley 2100 and > the Fluke 8845A. The Fluke is the best. The Agilent kicks a huge > amount of noise from the VF display into the input terminals. Ha... I had just mentioned all that noise to Joerg yesterday as I was hunting around for noise sources entering a receiver! Good to know we don't have a busted 34401 and it really is "just" poor design. :-( > The Fluke has the nicest menus, too. Both the K and the A can be > really obtuse menu-wise. I've never figured out why there seems to be little correlation between instrument cost and whether or not it gets a nice dot-matrix LCD/VFD/whatever vs. just a segment-mode display. Similarly there seems to be little correlation between the quality of the menu structures/input means and, e.g., how much screen real estate is avaialble. ---Joel
From: John Larkin on 12 Mar 2010 23:57 On Fri, 12 Mar 2010 20:19:12 GMT, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >On a sunny day (Fri, 12 Mar 2010 09:19:04 -0800) it happened John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in ><2jtkp5l6640dtc9b5tujet830kbqtap7i4(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. >> >>Does your e5 multimeter resolve microvolts? If not, it's useless for >>designing thermocouple stuff. > >Use a LM335, faster, cheaper, better :-) Try welding one of those to the stator of a jet engine. John
From: Jan Panteltje on 13 Mar 2010 08:17
On a sunny day (Fri, 12 Mar 2010 15:03:42 -0600) it happened John Fields <jfields(a)austininstruments.com> wrote in <8talp59g6d4lma3q6p93ttnnsn4cnm6m71(a)4ax.com>: >On Fri, 12 Mar 2010 20:15:16 GMT, Jan Panteltje ><pNaonStpealmtje(a)yahoo.com> wrote: > >>On a sunny day (Fri, 12 Mar 2010 09:33:25 -0800) it happened D from BC >><myrealaddress(a)comic.com> wrote in <MPG.26041ac522f727379896f0(a)209.197.12.12>: >> >>>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. >> >>I have a controlled current souce. >>Stuff 1 A through the .1 resistor and measure the voltage drop? > >--- >And you've determined the accuracy of the current source and the >resistor, how??? > >JF The question was not about accuracy, but how to measure .1 Ohm. |