What are 6.5 Digit Multimeters Good For?
in [Design]
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From: AZ Nomad on 12 Mar 2010 15:56 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? That's how a four wire ohmeter works. By use separate pairs to supply current and measure voltage, you mostly eliminate the effects of the resistance of the probe.
From: D from BC on 12 Mar 2010 16:00 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.
From: John Fields on 12 Mar 2010 16:03 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
From: John Fields on 12 Mar 2010 16:31 On Fri, 12 Mar 2010 20:33:42 GMT, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >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? --- If you can't understand it in plain English, what makes you think you'll be any less confused in "electronics English", whatever that may be? The point I was making was that your statement that 6.5 digit multimeters aren't needed is wrong, since without one you wouldn't be able to determine the accuracy of the cheap multimeter. JF
From: Spehro Pefhany on 12 Mar 2010 16:36
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. A potentially bigger problem is the BFC across the output, which means you might get a very high current for a while, enough to destroy transistors etc. if the output cap is charged to a high enough voltage. The current will eventually settle down to the limit setting, but that could be small consolation if you've fried something. |