> I checked with my (German) electronic supplier (www.reichelt.de) and > found these two pots: > > for $8: 20K, 10 turn, at temperature coefficient the specs say: "20ppm/ > degC (standard values, wire > only)"http://www.reichelt.de/?ACTION=3;ARTICLE=2544;PROVID=2402 > > for $0.50: 20K, 25 turn, but cermet with > 100ppm/degChttp://www.reichelt.de/?ACTION=3;ARTICLE=2722;PROVID=2402 > > So probably the first one, right? But does it really have such a small > temperature coeffient? The "standard values, wire only" confuses me. > > Jens
Cermet (100ppm, 0.01% ) is good enough for what you're doing. Mouser (here in the US) has wirewounds for only a buck or two, so its tempting. Its just that there's a lot of cheap stuff floating around, especially if you're in a place like Los Angeles (my local), where we're a gateway for all the stuff coming in from China. In dowtown L.A. there are districts where you can get all things fresh out of China. A toy district, a consumer electronics district, restaurant supply section, .... Its all crap, but its cheap crap. Great for party favors, but not for something that you need to rely on. Just stay away from parts where you can't reference a datasheet. That 20ppm part is way to expensive, and much tighter than your needs. 'Wire only' may either mean wire leads, or wirewound (?) There's a point of diminishing return, where its gets way too expensive for only minor improvements. Like using metrology grade resistors: http://www.vishay.com/docs/63186/z203.pdf Or super high end stereo equipment. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
