From: root@elektro.cmhnet.org (Charlie Smith)
Newsgroups: rec.motorcycles
Subject: Re: Pocket size multimeter
Summary: Arrrgh Pttoooiiee!
Date: 9 Oct 92 14:59:47 GMT
Article-I.D.: elektro.1992Oct9.145947.3659
Followup-To: charlie@elektro.cmhnet.org
Distribution: usa
Organization: Why do you suspect that?

Maybe I'll change my mind about supporting a rec.motorcycles.tech group.

I propose that the following, and all the rest of this thread be moved to
either rec.motorcycles.tech and/or alt.dweebs.proving.whose.smartest


Charlie Smith   charlie@elektro.cmhnet.org  csmith@dsac.dla.mil  whois ces10
MOA# 52888, RA# 15633, DoD# 0709, AMA# 574722, Buckey Beemers 411, BK Ohio V
BMW K1100-LT, R69S, R27 and other even less worthwhile [ 2 | 3 ] wheel stuff
            {  Friends don't let friends ride Japanese bikes  }
...........................................................................

In article <jlp.718561688@wink> jlp@blink.att.com (Jon Peticolas(x7058)) writes:
>thompson@Apple.COM (Paul Thompson) writes:
>
>>jlp@blink.att.com (Jon Peticolas(x7058)) writes:
>
>>>thompson@Apple.COM (Paul Thompson) writes:
>
>>>>Placing a 1uF capacitor between the leads should solve this problem.
>
>>>I'm unconvinced, I might try it, but I've looked at ignition noise
>>>with a 'scope (points, coil and condensor - electronic ignition may 
>>>differ) and thar's alot of energy in them spikes. A pi network might
>>>do it but....
>
>>Oscilloscopes measure voltage, not energy.  
>
>DUH.. Nevertheless, if you can see multi-volt high frequency 
>spikes at the terminals of a sizable lead-acid battery, it is 
>reasonable to extrapolate from those voltage/frequency measurements 
>and the load in question, the conclusion that there is more energy 
>in those spikes than can be suppressed with a mere 1uF cap. Noise 
>like this is what causes automotive radio manufacturers to place 
>large inductors (AKA chokes) on the power supply leads of their equipment.
>
>>If the 1uF cap still isn't enough (and I bet it is), then put a 10K 
>>resistor in series with one of the leads.  
>
>I see, a series resistor, a parallel capacitor, one more cap and
>you've got a pi network.
>
>>Which brings up yet advantage to digital meters - high
>>input impedance!
>
>Of negligible value in the environment under discussion. 
>In fact high impedance, fast response times and low capacitive 
>load work against you when making simple voltage measurments 
>in a noisy environment.
>
>>>>Then you can get the advantages of a digital multimeter - it's more
>>>>accurate, more rugged, more reliable, 
>
>>>Don't buy it. My cheap analog meters have taken some serious abuse
>>>and survived. My DVM has a LCD display that mere moisture makes 
>>>unreadable.  It also requires batteries. I can leave a cheap analog 
>>>meter in my tail pack/glove box for years and when I pull it out
>>>some dark night on the side of the road I'm not going to be stopped by
>>>dead batteries.
>
>>Well, my cheap analog meters break when I drop them, and the lithium
>>batteries in my DMM are good for several years.
>
>Can I help it if you're buying crap meters? And for that matter
>with the sterling reliability of the various heaps I ride/drive,
>it may well be years before I pull that meter out on the side of 
>some dark road miles from anywhere I could possibly buy a replacement
>lithium battery for a digital volt meter.
>
>>>>cheaper.
>
>>>On what planet?
>
>>Earth.  I'm sorry, I neglected to check where you were posting from.
>
>New Jersey, arguably not in the same galaxy. Around here DVMs 
>usually run about twice the price of a comparable analog meter.
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