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Date:         Fri, 27 Aug 1999 02:51:37 -0700
Reply-To:     Coby Smolens <cobys@WELL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Coby Smolens <cobys@WELL.COM>
Subject:      Re: Which Voltmeter to use?
Comments: To: David Beierl <dbeierl@IBM.NET>
In-Reply-To:  <4.2.0.58.19990826190308.0711e6c0@pop01.ny.us.ibm.net>
Content-Type: text/plain; charset="iso-8859-1"

I'm gonna check this in the literature tomorrow - I seem to remember that although the readings you see on-screen on a good DMM, whether numerical output or simulated analog (the little bar graph thingy that approximates a moving needle) are "averaged", the min-max feature works differently. Since it doesn't have to produce real-time displays it records actual minimum and maximum readings and holds them in memory until one requests them. Thus, if the V. drops to zero, even for a thousandth of a second, that fact will be captured by the machine. Or have I been bamboozled?

Incidentally, my meter of choice for years was the Fluke 88, but I switched to the Blue Point (Snap-On) version recently and I'm regretting it. I switched because the Fluke display was losing it (couldn't tell a three from a two anymore, etc.) and figured the cost of repair would be prohibitive. Also I liked the idea that the BP unit has temperature measuring capability built in, unlike the Fluke which provides a temp-transducer gizmo -- for an extra couple hundred clams. But the d*** BP temp sensor was the first thing to fail, just when the Snap-On truck stopped coming to our neck of the woods. Again.

> -----Original Message----- > From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf > Of David Beierl > Sent: Thursday, August 26, 1999 4:10 PM > To: vanagon@GERRY.VANAGON.COM > Subject: Re: Which Voltmeter to use? > > > At 14:31 8/26/99 -0700, Coby Smolens wrote: > >I like David's list, I would add only one thing to the "should-have" > >section: Min-max record. This is invaluable (read that extremely > valuable) > >in finding "drop outs", as in when a bad temp T2 sensor in an > aircooled van > > Yes, wonderful feature, sorry I forgot it. Just bear in mind that a > typical digital meter integrates (for this context you can think > "averages") the input for usually a second or two, so you won't see > anything that doesn't last longer than that (and will get strange readings > on values that change faster than that -- that's why the O2 sensor reading > jumps around on the display when in fact it's varying rapidly but smoothly > up and down). Every time the display blinks or updates it has > completed an > integration cycle. If you need faster response than that you're probably > looking at a 'scope. > > The bargraph display that a lot of meters have works faster and less > accurately than the digital display, but even it takes maybe > 1/4-1/2 second > to update. > > There are meters with much faster response times, but they are > $exotic$ beasts. > > david > David Beierl - Providence, RI > '84 Westy "Dutiful Passage" > '85 GL "Poor Relation" >


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