Bad resistors
in [Design]
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From: John Larkin on 23 Jun 2010 12:30 On Wed, 23 Jun 2010 08:37:52 -0700, DrParnassus <DrParnassus(a)hereforlongtime.org> wrote: >On Wed, 23 Jun 2010 07:05:09 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>Extech makes nice stuff. I think FLIR bought them to keep them from >>introducing a competitive IR imager. >> >>John > > Total bullshit. > > Extexh did not nor does not have the expertise to make an IR imager. > > I worked for an IR instrument maker, and FLIR buys calibration >equipment from them, and never felt threatened by our IR imager, which >has been around since before extech even existed. > > Raytheon or Square-D is a bigger threat in that market, and I am sure >that FLIR has no worries about them either. FLIR has a main market niche >that nobody encroaches on. > > Extech was NEVER a player in IR and especially not ANY military IR, and >any gear they did carry, they bought elsewhere and put their name on it. > > You're a goddamned idiot, as usual. http://www.extechstore.com/extech-irc40.aspx One day in the not-so-far future you'll be able to buy thermal imagers at Home Depot for under $250, eventually under $100. John
From: DrParnassus on 23 Jun 2010 12:30 On Wed, 23 Jun 2010 08:50:37 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >Too bad about the noise. A single 0603 100M thickfilm would have been >cheap and a lot less hassle. 0603 and 100M. That just sounds funny. Like simply looking at it could change the value between the nodes.
From: DrParnassus on 23 Jun 2010 12:32 On Wed, 23 Jun 2010 16:00:03 +0000 (UTC), Cydrome Leader <presence(a)panix.com> wrote: >DrParnassus <DrParnassus(a)hereforlongtime.org> wrote: >> On Tue, 22 Jun 2010 21:58:52 +0000 (UTC), Cydrome Leader >> <presence(a)panix.com> wrote: >> >>>what's the color code for M again? >> >> Wow, you really are a fresh out of or still in school know nothing >> dweeb. > >So do people describe you as dull, humorless and quick to use childish >insults like "dweeb"? It was not an insult. Your question above, and your inability to find the answer yourself, proves to everyone just where your head is at, boy. Sorry to be the bearer of the facts, Jack.
From: DrParnassus on 23 Jun 2010 12:33 On Wed, 23 Jun 2010 09:10:07 -0700 (PDT), George Herold <gherold(a)teachspin.com> wrote: >Was this 1/f noise? Noise that only showed up when you drove some >current through them? > >George H. It usually is 'one over f' noise.
From: John Larkin on 23 Jun 2010 12:35
On Wed, 23 Jun 2010 09:10:07 -0700 (PDT), George Herold <gherold(a)teachspin.com> wrote: >On Jun 23, 11:50�am, John Larkin ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >> On Wed, 23 Jun 2010 08:24:02 -0700, DrParnassus >> >> >> >> >> >> <DrParnas...(a)hereforlongtime.org> wrote: >> >On Wed, 23 Jun 2010 19:28:15 +1000, Sylvia Else <syl...(a)not.here.invalid> >> >wrote: >> >> >>On 23/06/2010 9:54 AM, DrParnassus wrote: >> >>> On Tue, 22 Jun 2010 21:51:47 GMT, Jan Panteltje >> >>> <pNaonStpealm...(a)yahoo.com> �wrote: >> >> >>>> Got 10 resistors on tape marked 2M7. >> >>>> Used one, circuit did not work right. >> >>>> Took some testing ... before I measured the resistors. >> >>>> Of the 10 several are 620 k and not 2M7. >> >>>> Bought fromwww.voti.nl, so beware. >> >>>> All are marked with the right color code for 2M7. >> >> >>>> New to me :-) >> >> >>> � �A normal handheld DVM barely measures 1MOhm correctly so anything up >> >>> there and over will not likely be easily measured with cheap handhelds. >> >> >>Still, you'd expect it to give the same wrong reading for the same >> >>resistances. >> >> >>Sylvia. >> >> > �That should be where their other clue comes from, because the readings >> >are typically not repeatable. >> >> But they are, to a fraction of a per cent. In the case of the carbon >> film resistor, I can hold the resistor body and see the resistor TC >> effect, also repeatable. High-ohm resistors do tend to have bad TCs. >> >> There is nothing different between using and measuring a 10K resistor >> or a 10M resistor. Or, assuming a little basic cleanliness, a 10G >> resistor. >> >> We recently needed a 100M metal-film resistor to use in a photodiode >> TIA thing. We tested a bunch of thickfilms and all had too much excess >> noise; the testing itself is a nuisance. We settled on some axial RC07 > >Was this 1/f noise? Noise that only showed up when you drove some >current through them? Right. I don't know if it was 1/f or wideband shot noise, or maybe both, but they were a lot noisier than the metal films, which seemed to be at the Johnson noise level, independent of bias. Capacitance limited our home-made test rig, so the noise spectrum was hard to decode. The bottom like is that the thickfilms were noisy and the Dales weren't. I was just thinking, in the shower, about developing a cool high-ohms resistance and resistor noise measurement box, USB interfaced. That would be fun. I probably won't do it, because it would be a fair amount of work with an unknown market. John |