Right. Stop and think.
-- John Larkin Highland Technology, Inc The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
Yes. The typical graph on the ADI data sheet has flat parts and steep parts.
-- John Larkin Highland Technology, Inc The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
I see, I skimmed too quickly sorry about that...
Could be. The old National LM121 precision preamp was like that (before they recycled the part number as a single version of the LM124, the dogs). When you zeroed out the offset, you also zeroed the drift. Pretty slick for its day.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Right. Well, that I2C A/D also has a voltage reference. I'm not sure how great it is but it seems to be good.
Carry on....
nd isolated
oces
s
MK, who is part vendor for these? One of the major U.S.s/UK, I hope. There is always a concern about mislabeled and falsified parts. You might think low-cost parts would not be profitable to fake. I'm not a conspiracy buff, but messing up our supply of reference devices would be a devious way to mess with manufacturing quality.. ;-) Cheers, Rich S.
I once bought a Motorola reference zener that came in a plastic tube with a signed certificate and a plot of voltage measured over 30 days. I don't expect that many modern parts are actually temperature tested on a production basis. They just fly through a test machine.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Statistical sampling? Like how they check that (almost all) pills coming off the assembly line at 1000 units/min have the proper amount of medication in them from the medicine-injector machine or (almost all) donut holes are the right diameter, test every Nth unit for sufficiently large N to apply the CLT and infer the population mean and standard deviation to some confidence.
Buy 100 small bags of potato chips, and note the labeled weight of the contents. Then actually weigh the chips. I've done it. None will be below the advertised weight, but none will be over by more than a fraction of the weight of the average chip.
After the bags are filled to a fraction-of-a-chip accuracy, and sealed, every bag is check weighed. I'd expect every pill to be inspected and weighed too.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Bags are weighed and fragments added to meet the threshold.
Pringles aren't done that way they meet the label spec by design and I expect pills are too.
-- Jasen.
No.
aka Partial Product Weighing Machine.
-- John Larkin Highland Technology, Inc The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
They came from RS Components in the UK - if I get to the stage of having evidence that will convince SED I'll take it up with RS - who probably have a better hotline to ADI than I do.
MK
Eventually, when I re-spin the pcb for this power supply I may replace the reference chip and using the processor's ADC with one of these: TI ADS122U04,
24 bit ADC with built in 5ppm (actually 30ppm worst case) voltage reference with typical 110ppm long term drift over 1000 hours and an on chip temperature sensor. Possible to calibrate over temperature by simple temperature sweep. Not sure about the drift - perhaps it'll have to demand re-cal.MK
The other thing that can cause this is die stress. SC70-package references are fairly famous for that. Routing a U around the reference is a good solution, but of course takes a hit in area and routability.
Cheers
Phil Hobbs
You can design any assembly-line process you like as best you can to meet the label spec "by design" and I would hope one would, but you gotta regularly verify that your process is, in fact, meeting the spec!
Neither the pills nor the assembly line is going to tell you if you just ask them like "hey can I ask you a personal question are all your parameters within tolerance today?"
Just weighing the pill doesn't give you the whole picture, part of the drug is medication and part of the pill is binder/other stuff, the weight could be right but the proportion could be off. The only way to verify that's right in the case of medication tablets is "destructively testing" i.e. a chemical analysis and you cant destructively test all your pills or you got no pills to sell.
ample.
well
may or
aard
Hey just sorta 1/2 lurking on this thread, but did anyone mention thermal stresses in the pcb... if it's held onto some piece of metal hard it could be stressed with temperature.
George H.
Watch the 34972A; You need slow/long measurement period and should avoid large voltage differences between subsequent measurements.
It pumps current into the measurement nodes at the time of switching and may also introduce CM loops, though 'isolated' from the internal meter.
RL
glue em back together. After unreacting them :)
NT
Thanks. Phill Hobbs mentioned that possibility. It would certainly explain the very odd "jumpy" behaviour of the Microchip LM4040 parts. I shall run a new test soon with a larger set of parts and over a wider temperature range.
MK
It's set up sensibly enough and the data doesn't look very symptomatic of the kind of problems you suggest. At some stage I can try using a DMM directly connected but that will limit me to testing less than 1 part per day !
MK
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