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From: firstname.lastname@example.org (N. Thornton)
Subject: Re: How to make/solder a circuit fast?
Date: 29 Sep 2002 06:15:32 -0700
References: <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: 29 Sep 2002 13:15:33 GMT
The little lost angel and Roger Johansson wrote:
>>Wouldn't it be easier to use a voltmeter to measure the DC and use
>>soundcard for the AC content of the same signal?
Bear in mind your sound card wont go much below 20Hz, and your DVM
sure wont reach 20Hz... so you're left with an unmeasured gap. And 5
or 10Hz fluctuations are entirely possible.
>It doesn't sound like you have any problems with the DC part of the
>signal, so why measure it.
I thought that was an issue needing monitoring. Thermal drift is no
rarity after all.
>Also, the other problem is I haven't managed to find a cheap DVM that
>can do 1~100mV good enough for measuring current.
It sounds easy to use an opamp to amplify that upto easily measured
>It is maybe not the fault of the voltmeter, if you use cables
Well, it IS. Because my Fluke measures it correctly. A 5A current
reads out 5.x mV on the Fluke. I get anything from 20mV to 40mV on
cheapo ones. I need like 3~4 of them for current readings, and 4
Flukes would really kill my budget.
4 opamps would come in at around 10 bucks for the ICs.
>>If you had used a piece of thick cable, as I told you months ago,
>>which gives you 10 times or a hundred times higher voltages, this
>>would be much less of a problem.
>heehee, I couldn't find thick cables here. When I asked for AWG10,
>people gave me blank looks. And the thickest they had, was a
>to cut and coil. I gave up on the idea very quickly.
Can't you use a row of parallel pieces of mains cable? Or if you want
ready-made thick, a set of car jump-starting leads.
>So I read the spec and found a whole lot of stuff I've never thought
>of when this testing idea first came to up :P
Lol, you like sticking your tongue out :)
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