What are 6.5 Digit Multimeters Good For?
in [Design]
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From: D from BC on 12 Mar 2010 12:33 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.
From: Wanderer on 12 Mar 2010 12:39 On Mar 12, 12:33 pm, D from BC <myrealaddr...(a)comic.com> wrote: > In article <hndc5b$37...(a)news.albasani.net>, pNaonStpealm...(a)yahoo.com > says... > > > > > > > On a sunny day (Thu, 11 Mar 2010 17:56:35 -0800) it happened D from BC > > <myrealaddr...(a)comic.com> wrote in <MPG.26033f321480b13989...(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. One use is to find shorts on circuit boards. The really accurate resistance measurement lets you home in on the offending part :)
From: Jim Thompson on 12 Mar 2010 12:44 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 -- | 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: John Larkin on 12 Mar 2010 13:08 On Fri, 12 Mar 2010 09:39:45 -0800 (PST), Wanderer <wanderer(a)dialup4less.com> wrote: >On Mar 12, 12:33�pm, D from BC <myrealaddr...(a)comic.com> wrote: >> In article <hndc5b$37...(a)news.albasani.net>, pNaonStpealm...(a)yahoo.com >> says... >> >> >> >> >> >> > On a sunny day (Thu, 11 Mar 2010 17:56:35 -0800) it happened D from BC >> > <myrealaddr...(a)comic.com> wrote in <MPG.26033f321480b13989...(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. > >One use is to find shorts on circuit boards. The really accurate >resistance measurement lets you home in on the offending part :) Get an adjustable power supply and set it to low volts, 1 amp current limit. Connect that to a pc board, to a trace or a shorted plane or something, then measure microvolt drops here and there. With a good DVM you can resolve micro-ohms. It's interesting to calculate the resistance of traces and actually measure them. Most pcb houses skimp on plating, so when you specify "1 oz" copper, you seldom get it. John
From: Joel Koltner on 12 Mar 2010 13:24
"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:mh0lp5t4e1abliki9ra07qgrpb9q56ej6k(a)4ax.com... > It's interesting to calculate the resistance of traces and actually > measure them. Most pcb houses skimp on plating, so when you specify "1 > oz" copper, you seldom get it. I figured that it's a somewhat open-loop process where they stick your board in a tank and set a timer (based on calculations of their chemistry and the size of your board) so it's probably no better than +/-20%... and apparently many customers aren't really relying on the spec anyway so only a few places bother measuring it for you. I wonder what the uniformity of plating is anyway though? It seems that it would be subject to "shadowing" and concentration effects just like etching is, and hence require agitation to make it more uniform. |