How can I transform the variation over temperature: 25 ppm/K to ppm/°C?
I was searching for the formula and all I could find was that 100 ppm/K = 100 ppm/°C.
Is this true?
Asked
Active
Viewed 9,198 times
5
Volker Siegel
- 1,076
- 2
- 12
- 26
electricalEN
- 103
- 1
- 7
3 Answers
19
Kelvin and Celsius are the same scale, but Kelvin is shifted so zero lines up with absolute zero while Celsius is shifted so zero lines up with the freezing point of water, for convenience. The step size of both are the same.
It is like how km can be used to measure distance from my hometown instead of your hometown to the same location. The size of each km is the same, but your reference point is different.
The difference is 273.15 K or °C. So 0 °C is 273.15 K, but that is absolute temperature. A ppm/K or ppm/C is a relative measurement that only cares about changes in temperature and in that case the 273.15 term appears twice, once for K and once for °C so it subtracts itself out of the equation.
Volker Siegel
- 1,076
- 2
- 12
- 26
DKNguyen
- 56,670
- 5
- 69
- 160
-
4I tend to argue that temperature differences should actually always be written in K, not in °C. Celsius isn't really a physical unit at all, just an affine scale. – leftaroundabout Oct 25 '19 at 13:31
-
@leftaroundabout Do you say "it's cold in here. Turn up the thermostat a couple of Kelvin" ;) – DKNguyen Oct 25 '19 at 13:34
-
usually I rather say “it's way too hot, turn off the bloody heating”! Or when I try to be polite, “please turn down the heating _a bit_”. – leftaroundabout Oct 25 '19 at 13:37
-
@DKNguyen - LOL... I'm actually going to start saying that! – Greenonline Oct 25 '19 at 20:37
11
Yes it is true because a change of 1 °C is the same as a change of 1 K.
Volker Siegel
- 1,076
- 2
- 12
- 26
Justme
- 147,557
- 4
- 113
- 291
-
I still can't see the link between the two. how can it be the same if they are in a different range? – electricalEN Oct 24 '19 at 12:21
-
2@todiOdi If x changed from 20 ºC to 21 ºC then there would be a 25 ppm change in y. If x changed from 293 K to 294 K then there would be a 25 ppm change in y. – Andrew Morton Oct 24 '19 at 12:28
-
1@todiOdi - see https://en.wikipedia.org/wiki/Thermodynamic_temperature – Peter Smith Oct 24 '19 at 12:28
-
3@todiOdi: Justme didn't say that C is the the same as K, he said a "change of 1C is the same as a change of 1K". – Curd Oct 24 '19 at 12:31
-
-
NXP (and now Nexperia) routinely use the term K for temperature effects in their datasheets. – Peter Smith Oct 24 '19 at 13:58
-
-
3
I was searching for the formula and all I could find was that 100 ppm/K = 100 ppm/°C.
Remember that the value that's changing is the measurement - resistance, voltage, current, intensity, length, etc. For example, the calibration of a range sensor may vary by 100 ppm/K which means that the distance measured may vary by 100 ppm (0.01%) for every one kelvin change.
Is this true?
Since the kelvin unit is the same as 1°C the statement is true.
Transistor
- 175,532
- 13
- 190
- 404
-
@VolkerSiegel, thanks for the edit but I rejected it. "Units: The names of all units start with a lower case letter except, of course, at the beginning of the sentence. There is one exception: in "degree Celsius" (symbol °C) the unit "degree" is lower case but the modifier "Celsius" is capitalized. Symbols: Unit symbols are written in lower case letters except for liter and those units derived from the name of a person (m for meter, but W for watt, Pa for pascal, etc.)." See NIST. – Transistor Oct 29 '19 at 17:20
-
Thank you, I thought the unit kelvin would be written upper case because it is derived from the name Lord Kelvin. – Volker Siegel Oct 29 '19 at 17:29