On Tuesday, December 14, 2021 at 5:40:50 PM UTC+11, John Doe wrote:> Anthony William Sloman <bill....@ieee.org> wrote: > > On Saturday, December 11, 2021 at 1:14:23 PM UTC+11, palli...@gmail.com wrote: > >> whit3rd > >> ======================== > > ===========> > > >> > > PT1000/PT100 is ~0.4%/C > >> > > >> > Oh, that's just about true for all classical metals; getting a non-PTAT (proportional to absolute temperature) resistor is a notable materials-science achievement. > >> > > >> > At 20 C, proportional to absolute temperature means about 0.0034 per kelvin; for copper, resistance goes 0.00386, for tungsten 0.0045, for aluminum 0.00429, for platinum 0.0039 ... > >> > > >> >The impure (alloyed) metals used for low tempco have very non-ideal meta llic nature. > >> > > >> ** " very non- ideal metallic nature" ??????? > >> > >> Could you please be bit more ambiguous ?? > >> > >> Cos some fuckheads here will imagine it makes sense. > > > > Back when I was in paid work we got a marketing talk from Vishay on their very low temperature coefficient resistors which could get below +/-5ppm per degree Celcius, if you were willing to buy their most expensive parts (which we were, if not all that often). > > > > They not only mucked about with the composition of the materials they laid down in their thin films, but they also figured in temperature generated strain by laying down material with one cofficient of thermal expansion on a substrate with a a different one. This is a longer way of saying that they got non-ideal behaviour. I can see whit3rd might have wanted to avoid testing your attention span (which isn't all that long).John Doe posted his usual drivel (which I've snipped)- he seems to be even more ignorant about low TC resistors than Phil Allison, and even more dedicated to being obnoxious. -- Bill Sloman, Sydney
Low coefficient NTC resistors?
Started by ●December 10, 2021
Reply by ●December 14, 20212021-12-14
Reply by ●December 14, 20212021-12-14
On a sunny day (Fri, 10 Dec 2021 22:50:31 +1100) it happened Sylvia Else <sylvia@email.invalid> wrote in <j1gt8aF63iuU1@mid.individual.net>:>Anyone aware of such a thing? > >Clearly, one can achieve that just by putting a thermistor in series >with an ordinary resistor, but my UPS seems to contain a single >component that behaves that way - perhaps less than 1% at 20 Celcius - >it's in the circuit that controls the battery charging float voltage. > >Did they perhaps exist 20 years ago (when my UPS was made), for some reason? > >SylviaUsed a simple Si diode as temp sensor in some equipment. -2 mV / degree C or there about, linear at that.
Reply by ●December 14, 20212021-12-14
On Friday, December 10, 2021 at 8:51:53 PM UTC-4, bill....@ieee.org wrote:> On Saturday, December 11, 2021 at 11:30:50 AM UTC+11, David Eather wrote: > > On 10/12/2021 9:50 pm, Sylvia Else wrote: > > > Anyone aware of such a thing? > > > > > > Clearly, one can achieve that just by putting a thermistor in series > > > with an ordinary resistor, but my UPS seems to contain a single > > > component that behaves that way - perhaps less than 1% at 20 Celcius - > > > it's in the circuit that controls the battery charging float voltage. > > > > > > Did they perhaps exist 20 years ago (when my UPS was made), for some > > > reason? > > > > lead acid batteries are temperature sensitive when recharging > All batteries - as electrochemical devices - are temperature sensitive > > https://en.wikipedia.org/wiki/Gibbs_free_energy > > If you scroll down to "In electrochemical thermodynamics" you will get to the Nernst Equation > > https://en.wikipedia.org/wiki/Nernst_equation > > which can be seen as the Gibbs Free energy equation for electrochemical systems - curiously, Nernst formulated it in 1888 some twelves years after Gibbs had published the more general formulation. Thermodynamics isn't easy to get your head around - even if you are as clever as Nernst, who eventually got a Nobel prize in 1920 for his work on the third law of thermodynamics. Once instilled, it does tend to stick - as an undergraduate in 1961 it took me a while to get my head around that particular bit of the chemistry course.I remember seeing bumper stickers that read, "Honk if you passed P-Chem". Thermo was the ball buster section of the ball buster P-Chem I course with Castellan who wrote a book and of course used it in his class. The book sucked! The part of the class that covered quantum mechanics was easier and better covered. -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
Reply by ●December 14, 20212021-12-14
On Friday, December 10, 2021 at 9:02:59 PM UTC-4, Sylvia Else wrote:> On 11-Dec-21 11:30 am, David Eather wrote: > > On 10/12/2021 9:50 pm, Sylvia Else wrote: > >> Anyone aware of such a thing? > >> > >> Clearly, one can achieve that just by putting a thermistor in series > >> with an ordinary resistor, but my UPS seems to contain a single > >> component that behaves that way - perhaps less than 1% at 20 Celcius - > >> it's in the circuit that controls the battery charging float voltage. > >> > >> Did they perhaps exist 20 years ago (when my UPS was made), for some > >> reason? > >> > >> Sylvia > > > > lead acid batteries are temperature sensitive when recharging > Yes, this is presumably the reason for the NTC resistor in the charging > circuit. But if it has a typical thermistor characteristic, then in this > particular implementation, the compensation will be out by a factor of > ten, which is probably worse than no compensation at all. > > I may have to remove it from the circuit to better characterise it.I worked on a design last year where the charging circuit had a thermistor to adjust the batter voltage. I pointed out the resistor was on a board near a motor and other power circuits that would certainly make the PWB hotter than the battery at the other end of the cabinet. The designer didn't care. He would often wax on about the various nits he had picked up over the years and yet could not understand something so simple as a temperature sensing thermistor needed to be thermally coupled to the battery rather than the motor the battery would be driving. -- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
Reply by ●December 15, 20212021-12-15
NOBODY likes this troll's contentless spam. After being spanked in the electronics repair group, it wants to annoy everybody. This nym-shifting stalker Corvid/Edward/others is upset because it will never again troll USENET without its nyms being exposed... =?UTF-8?Q?C=c3=b6rvid?= <bl@ckbirds.org> =?UTF-8?B?8J+QriBDb3dzIGFyZSBOaWNlIPCfkK4=?= <nice@cows.moo> Banders <snap@mailchute.com> Covid-19 <always.look@message.header> Corvid <bl@ckbirds.net> Corvid <bl@ckbirds.org> Cows Are Nice <cows@nice.moo> Cows are nice <moo@cows.org> Cows are Nice <nice@cows.moo> dogs <dogs@home.com> Edward H. <dtgamer99@gmail.com> Edward Hernandez <dtgamer99@gmail.com> Great Pumpkin <pumpkin@patch.net> Jose Curvo <jcurvo@mymail.com> Local Favorite <how2recycle@palomar.info> Peter Weiner <dtgamer99@gmail.com> Sea <freshness@coast.org> Standard Poodle <standard@poodle.com> triangles <build@home.com> and others... -- Edward Hernandez <dtgamer99@gmail.com> wrote:> Path: eternal-september.org!reader02.eternal-september.org!2.eu.feeder.erje.net!feeder.erje.net!newsfeed.xs4all.nl!newsfeed9.news.xs4all.nl!news-out.netnews.com!news.alt.net!fdc2.netnews.com!peer03.ams1!peer.ams1.xlned.com!news.xlned.com!peer01.ams4!peer.am4.highwinds-media.com!news.highwinds-media.com!fx02.ams4.POSTED!not-for-mail > From: Edward Hernandez <dtgamer99@gmail.com> > Subject: Re: Low coefficient NTC resistors? > Newsgroups: sci.electronics.design,free.spam > References: <j1gt8aF63iuU1@mid.individual.net> <bc47ce70-539b-48dd-9469-9ad789009e31n@googlegroups.com> <2085e59f-c355-447e-be76-fc9b9b4c3604n@googlegroups.com> <0d6a94d9-e1e5-45c9-a353-41ba02182ff5n@googlegroups.com> <54d7ef11-d692-4e27-b3d6-6dc820a380ean@googlegroups.com> <sp9e9b$q3d$1@dont-email.me> > Lines: 22 > Message-ID: <exXtJ.1173034$mMM3.1091099@usenetxs.com> > X-Complaints-To: https://www.astraweb.com/aup > NNTP-Posting-Date: Tue, 14 Dec 2021 07:16:26 UTC > Date: Tue, 14 Dec 2021 07:16:26 GMT > X-Received-Bytes: 1600 > Xref: reader02.eternal-september.org sci.electronics.design:654848 free.spam:16807 > > The John Doe troll stated the following in message-id > <sdhn7c$pkp$4@dont-email.me>: > >> The troll doesn't even know how to format a USENET post... > > And the John Doe troll stated the following in message-id > <sg3kr7$qt5$1@dont-email.me>: > >> The reason Bozo cannot figure out how to get Google to keep from >> breaking its lines in inappropriate places is because Bozo is >> CLUELESS... > > And yet, the clueless John Doe troll has itself posted yet another > incorrectly formatted USENET posting on Tue, 14 Dec 2021 06:40:44 -0000 > (UTC) in message-id <sp9e9b$q3d$1@dont-email.me>. > > This posting is a public service announcement for any google groups > readers who happen by to point out that the John Doe troll does not even > follow it's own rules that it uses to troll other posters. > > mFpwbmxNA8bW > > >
Reply by ●December 15, 20212021-12-15
The John Doe troll stated the following in message-id <sdhn7c$pkp$4@dont-email.me>:> The troll doesn't even know how to format a USENET post...And the John Doe troll stated the following in message-id <sg3kr7$qt5$1@dont-email.me>:> The reason Bozo cannot figure out how to get Google to keep from > breaking its lines in inappropriate places is because Bozo is > CLUELESS...And yet, the clueless John Doe troll has itself posted yet another incorrectly formatted USENET posting on Wed, 15 Dec 2021 18:12:56 -0000 (UTC) in message-id <spdb78$p47$3@dont-email.me>. This posting is a public service announcement for any google groups readers who happen by to point out that the John Doe troll does not even follow it's own rules that it uses to troll other posters. 1jqv3YkW8CYw
Reply by ●December 16, 20212021-12-16
On Mon, 13 Dec 2021 22:40:09 -0800 (PST), Anthony William Sloman <bill.sloman@ieee.org> wrote:>Back when I did one, back in 1979, you needed a lot of gain in that one op = >amp. I ended up going with four - it made the low pass filtering a lot easi= >er. My bosses got tetchy, so I had to draw the one, two and three op amp op= >tions. Electrotherm had a bulk deal on the uA715, so the one amplifier opti= >on wasn't all that expensive, but nothing else around at the time had that = >much gain.Odd, RTDs have such high output even a single LM358 should be about good enough for *most* purposes unless you're running them at much lower than normal current or looking for off-label uK performance (which I remember you were doing with thermistors). At 0.5mA you get ~200uV/�C with a Pt100 ohm DIN RTD. Interchangability is maybe 1/3�C for inexpensive ones (at room temperature) and a degree or two at extremes, so for normal purposes- any modern op-amp assuming you don't mind trimming the offset. Coincidentally, about the same output as you get measuring temperature with silicon BJT(s) operated at 10:1 current ratio.>The linearising involved a smidgen of positive feedback which fr= >ightened the guy who took over the project, and nobody could make him see s= >ense.Shouldn't be too hard to show mathematically that the net feedback is strongly negative for all sensible RTD values. And that break protection is in the safe direction. He probably would be terrified (with some justification) by an enhanced Howland current source. The cool thing is that the same resistor that linearizes the RTD can be used to avoid having an active current source for excitation. Just a resistor from a reference voltage will do for excitation- there is no advantage to using a current source.>--=20 >Bill Sloman, Sydney-- Best regards, Spehro Pefhany
Reply by ●December 16, 20212021-12-16
On 14-Dec-21 8:04 pm, Jan Panteltje wrote:> On a sunny day (Fri, 10 Dec 2021 22:50:31 +1100) it happened Sylvia Else > <sylvia@email.invalid> wrote in <j1gt8aF63iuU1@mid.individual.net>: > >> Anyone aware of such a thing? >> >> Clearly, one can achieve that just by putting a thermistor in series >> with an ordinary resistor, but my UPS seems to contain a single >> component that behaves that way - perhaps less than 1% at 20 Celcius - >> it's in the circuit that controls the battery charging float voltage. >> >> Did they perhaps exist 20 years ago (when my UPS was made), for some reason? >> >> Sylvia > > Used a simple Si diode as temp sensor in some equipment. > -2 mV / degree C or there about, linear at that. > > >In the end, it became apparent that this thermistor is in parallel with an ordinary resistor far away on the board. Also, that the temperature compensation it provides is much too low. That will be fixed, along with putting the thermistor on the batteries. Sylvia.
Reply by ●December 16, 20212021-12-16
On 15-Dec-21 3:06 am, Rick C wrote:> On Friday, December 10, 2021 at 9:02:59 PM UTC-4, Sylvia Else wrote: >> On 11-Dec-21 11:30 am, David Eather wrote: >>> On 10/12/2021 9:50 pm, Sylvia Else wrote: >>>> Anyone aware of such a thing? >>>> >>>> Clearly, one can achieve that just by putting a thermistor in series >>>> with an ordinary resistor, but my UPS seems to contain a single >>>> component that behaves that way - perhaps less than 1% at 20 Celcius - >>>> it's in the circuit that controls the battery charging float voltage. >>>> >>>> Did they perhaps exist 20 years ago (when my UPS was made), for some >>>> reason? >>>> >>>> Sylvia >>> >>> lead acid batteries are temperature sensitive when recharging >> Yes, this is presumably the reason for the NTC resistor in the charging >> circuit. But if it has a typical thermistor characteristic, then in this >> particular implementation, the compensation will be out by a factor of >> ten, which is probably worse than no compensation at all. >> >> I may have to remove it from the circuit to better characterise it. > > I worked on a design last year where the charging circuit had a thermistor to adjust the batter voltage. I pointed out the resistor was on a board near a motor and other power circuits that would certainly make the PWB hotter than the battery at the other end of the cabinet. The designer didn't care. He would often wax on about the various nits he had picked up over the years and yet could not understand something so simple as a temperature sensing thermistor needed to be thermally coupled to the battery rather than the motor the battery would be driving. >As I've indicated in my reply to Jan, I believe that the circuit in my UPS is not providing anything like the required compensation. Perhaps the designer's remit was to provide some temperature compensation, so he did, without caring whether it was the correct amount. Sylvia.
Reply by ●December 16, 20212021-12-16
On Thursday, December 16, 2021 at 5:20:17 PM UTC+11, Spehro Pefhany wrote:> On Mon, 13 Dec 2021 22:40:09 -0800 (PST), Anthony William Sloman <bill....@ieee.org> wrote: > > >Back when I did one, back in 1979, you needed a lot of gain in that one op amp. I ended up going with four - it made the low pass filtering a lot easier. My bosses got tetchy, so I had to draw the one, two and three op amp options.> ElectrothermActually Eurotherm. I was working for Chessel Recorders at the time (which was part of the Eurotherm group. > had a bulk deal on the uA715, so the one amplifier option wasn't all that expensive, but nothing else around at the time had that much gain.> > Odd, RTDs have such high output even a single LM358 should be about > good enough for *most* purposes unless you're running them at much > lower than normal current or looking for off-label uK performance > (which I remember you were doing with thermistors).It certainly wasn't for micro-Kelvin applications. Chessel Recorders were manufactured in high volume for low end applications like bakeries and breweries.> At 0.5mA you get ~200uV/°C with a Pt100 ohm DIN RTD. Interchangability > is maybe 1/3°C for inexpensive ones (at room temperature) and a degree > or two at extremes, so for normal purposes- any modern op-amp assuming > you don't mind trimming the offset.If you wanted 10 degrees to fill the 0 to 10V span of the chart recorder that's a gain of 5000, which is quite high. It's forty years ago, so the details are hazy.> Coincidentally, about the same output as you get measuring temperature with silicon BJT(s) operated at 10:1 current ratio. > > >The linearising involved a smidgen of positive feedback which frightened the guy who took over the project, and nobody could make him see sense. > > Shouldn't be too hard to show mathematically that the net feedback is strongly negative for all sensible RTD values. And that break protection is in the safe direction.He seemed to think that any positive feedback was risky https://en.wikipedia.org/wiki/Geometric_series makes the point that the sum with any r less than one is finite, which isn't exactly higher mathematics, and r was about +0.003> He probably would be terrified (with some justification) by an enhanced Howland current source. > > The cool thing is that the same resistor that linearizes the RTD can be used to avoid having an active current source for excitation.That wasn't the approach I was using, We just pushed the current through the sense resistor up a bit as it got hotter to compensate for the slow decline in sensitivity with rising temperature. Very crude.> Just a resistor from a reference voltage will do for excitation- there is no advantage to using a current source.There is a bit. A Wheatstone bridge throws away a bit of the sensitivity - in a symmetrical bridge, half of it. It certainly isn't worth the trouble of going to current source excitation. -- Bill Sloman, Sydney
