At 09:34 PM 8/10/2011, Jouni Valkonen wrote:
Galantini stated a fact from manual: «4- The
thermometers have a margin of error of +/- 0,05 Celsius»
Lomax replied with speculation: «This depends
on the probe. However, from other data (such as
probe rated temperature of 150 C.) the probe has
an accuracy of +/- 0.4 C. He's greatly
overstated the accuracy, it seems, and that is
crucial here. The *resolution* is 0.1 C., and I
think he munges that into +/- 0.05.»
Thermometer must be calibrated in respect of
boiling point of water (or other known
temperature that is relevant for what is
measured) before it can be used for accurate
measurements. Without calibration, it's accuracy
is just ±0.4°C. But thermometer
reproducibility is ±0.05°C and this means that
thermometer gives same reading with this
accuracy in two consecutive measurements.
No, the resolution is 0.1 degree.
As Mats Lewan calibrated the thermometer that
boiling point was 99.6°C, altough real boiling
point in Bologna in that particular day was
99.9°C. This is what it meas that thermometer
accuracy is ±0.4. But relative accuracy or
precision or reproducibility is always higher in
thermometer than the resolution of display. In
this case digits are by one decimal, hence ±0.05°C accuracy.
This assumes that if one sees, say, 100.1 C.,
that the real temperature is between 100.05 and
100.15. However, the calibration, even if done
with a perfect temperature standard, would only
be good to that range. The maximum error in the
actual measurement, then, will be +/- 0.1 degree,
plus a little, so that it *might* be off by
another digit under some circumstances. I.e,
suppose the calibration reads 100.0, but the
internals of the meter is saying 100.0499. So we
then have a systematic error of -0.0499 degree.
Then we go to measure a temperature of 100.0998
degrees. The meter will "read" 100.0499, rounding
down to 100.0. An error of almost 0.1 degree.
With fancy calibration you might be able to
improve this. You'd adjust to the center between flips of a digit.
I have said this before, but it seems that you
are not familiar with this calibration issue.
Actually, I wrote extensively about it.
But it was from Galantine vulgar mistake to
think that reproducibility or resolution
(±0.05) is the same thing as absolute accuracy without calibration (±0.4).
But, no other negative comments on your
Galantini critique. It was quite accurate up to precision of ±0.05.
Why, thanks. However, the resoluton is 0.1 C. He
made up the 0.05. The manufacturer says 0.1, and
that's how these things work. It's a displayed
resolution, it's not really a +/- thing.
