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
Low coefficient NTC resistors?
Started by ●December 10, 2021
Reply by ●December 10, 20212021-12-10
On Fri, 10 Dec 2021 22:50:31 +1100, Sylvia Else <sylvia@email.invalid> 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? > >SylviaYes, I have purchased custom positive temperature coefficient resistors in relatively small lots (10K, if memory serves). They're usually in around the tempco of metals and alloys. (a few thousand ppm per degree C, positive and fairly linear. You can find a few values of nickel thin film resistors on Digikey that have a similar tempco. Putting a resistor in series with a conventional NTC does not work so well over a wide temperature range because of the nonlinearity of the thermistor. -- Best regards, Spehro Pefhany
Reply by ●December 10, 20212021-12-10
On Friday, December 10, 2021 at 11:43:16 PM UTC+11, Spehro Pefhany wrote:> On Fri, 10 Dec 2021 22:50:31 +1100, Sylvia Else <syl...@email.invalid> > 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? > > Yes, I have purchased custom positive temperature coefficient > resistors in relatively small lots (10K, if memory serves). > > They're usually in around the tempco of metals and alloys. (a few > thousand ppm per degree C, positive and fairly linear. > > You can find a few values of nickel thin film resistors on Digikey > that have a similar tempco. > > Putting a resistor in series with a conventional NTC does not work so > well over a wide temperature range because of the nonlinearity of the > thermistor.My impression was that nickel thin film resistors were the poor man's platinum resistance sensor. They had around the same temperature coefficient - the resistance was more or less proportional to absolute temperature around room temperature. They weren't as good as platinum resistance sensors - for one thing they oxidise if they get too hot. Wikipedia says that they go non-linear about about 300 Celcius. https://www.prelectronics.com/the-fundamentals-of-rtd-temperature-sensors/ https://en.wikipedia.org/wiki/Resistance_thermometer -- Bill Sloman, Sydney
Reply by ●December 10, 20212021-12-10
fredag den 10. december 2021 kl. 12.50.41 UTC+1 skrev Sylvia Else:> 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? >PT1000/PT100 is ~0.4%/C
Reply by ●December 10, 20212021-12-10
On Fri, 10 Dec 2021 05:43:39 -0800 (PST), Anthony William Sloman <bill.sloman@ieee.org> wrote:>On Friday, December 10, 2021 at 11:43:16 PM UTC+11, Spehro Pefhany wrote: >> On Fri, 10 Dec 2021 22:50:31 +1100, Sylvia Else <syl...@email.invalid> >> 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? >> >> Yes, I have purchased custom positive temperature coefficient >> resistors in relatively small lots (10K, if memory serves). >> >> They're usually in around the tempco of metals and alloys. (a few >> thousand ppm per degree C, positive and fairly linear. >> >> You can find a few values of nickel thin film resistors on Digikey >> that have a similar tempco. >> >> Putting a resistor in series with a conventional NTC does not work so >> well over a wide temperature range because of the nonlinearity of the >> thermistor. > >My impression was that nickel thin film resistors were the poor man's platinum resistance sensor. They had around the same temperature coefficient - the resistance was more or less proportional to absolute temperature around room temperature. They weren't as good as platinum resistance sensors - for one thing they oxidise if they get too hot. Wikipedia says that they go non-linear about about 300 Celcius. > >https://www.prelectronics.com/the-fundamentals-of-rtd-temperature-sensors/ > >https://en.wikipedia.org/wiki/Resistance_thermometerPropietary nickel alloy base metal sensors are used in HVAC applications by folks like Honeywell. Ni120 sensors (wound and now thin film) are traditionally used in some applications like bearing and motor stator winding temperature (sometimes they use Cu RTDs for the latter). The SMT 0603 etc. Vishay ones I was mentioning are pretty awful for sensors, almost a 10% tolerance on Tempco and a max temperature of 150�C minus self-heating so their applications would be limited. The ones I sourced from a Japanese factory had much tighter tolerance on tempco. -- Best regards, Spehro Pefhany
Reply by ●December 10, 20212021-12-10
On Fri, 10 Dec 2021 10:16:46 -0500, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:>On Fri, 10 Dec 2021 05:43:39 -0800 (PST), Anthony William Sloman ><bill.sloman@ieee.org> wrote: > >>On Friday, December 10, 2021 at 11:43:16 PM UTC+11, Spehro Pefhany wrote: >>> On Fri, 10 Dec 2021 22:50:31 +1100, Sylvia Else <syl...@email.invalid> >>> 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? >>> >>> Yes, I have purchased custom positive temperature coefficient >>> resistors in relatively small lots (10K, if memory serves). >>> >>> They're usually in around the tempco of metals and alloys. (a few >>> thousand ppm per degree C, positive and fairly linear. >>> >>> You can find a few values of nickel thin film resistors on Digikey >>> that have a similar tempco. >>> >>> Putting a resistor in series with a conventional NTC does not work so >>> well over a wide temperature range because of the nonlinearity of the >>> thermistor. >> >>My impression was that nickel thin film resistors were the poor man's platinum resistance sensor. They had around the same temperature coefficient - the resistance was more or less proportional to absolute temperature around room temperature. They weren't as good as platinum resistance sensors - for one thing they oxidise if they get too hot. Wikipedia says that they go non-linear about about 300 Celcius. >> >>https://www.prelectronics.com/the-fundamentals-of-rtd-temperature-sensors/ >> >>https://en.wikipedia.org/wiki/Resistance_thermometer > >Propietary nickel alloy base metal sensors are used in HVAC >applications by folks like Honeywell. > >Ni120 sensors (wound and now thin film) are traditionally used in some >applications like bearing and motor stator winding temperature >(sometimes they use Cu RTDs for the latter). > >The SMT 0603 etc. Vishay ones I was mentioning are pretty awful for >sensors, almost a 10% tolerance on Tempco and a max temperature of >150�C minus self-heating so their applications would be limited. The >ones I sourced from a Japanese factory had much tighter tolerance on >tempco.The ZNI1000 nickel RTD is a cool part. It can be linearized with one resistor. Of course, ic temp sensors are cheap and can be had analog or SPI. -- Father Brown's figure remained quite dark and still; but in that instant he had lost his head. His head was always most valuable when he had lost it.
Reply by ●December 10, 20212021-12-10
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? > > SylviaThe only thing that comes to mind is a diode. 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
Reply by ●December 10, 20212021-12-10
Stupider than Anyone Else wrote:> > Anyone aware of such a thing? >** Yawnnnnnnnn...> 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. >** Thermal tracking is often built inside the charging controller IC used. https://www.ti.com/lit/ds/symlink/bq24450.pdf?ts=1639171712003&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FBQ24450 ..... Phil
Reply by ●December 10, 20212021-12-10
On Fri, 10 Dec 2021 22:50:31 +1100, Sylvia Else <sylvia@email.invalid> 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? > >SylviaCarbon comp resistor, roughly -1200 ppm/c. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
Reply by ●December 10, 20212021-12-10
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? > > Sylvialead acid batteries are temperature sensitive when recharging
