At 09:17 PM 8/10/2011, you wrote:
Abd ul-Rahman Lomax <<mailto:a...@lomaxdesign.com>a...@lomaxdesign.com> wrote:
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.
5- I made my measurements only when the temperature was exactly 100.1 Celsius
Plus or minus 0.4 C.
I have a number of electronic and red-liquid
thermometers. I have never heard of one with
higher resolution than accuracy, after you
calibrate. That makes no sense. If it was
plus/minus 0.4 deg C they would set the display
to show only half-degrees. (Some do that.)
No, they wouldn't. You can use the resolution to
make temperature comparisons. Jed, maybe I
misread the specifications. I did not, however,
make this up. And I do know for a fact that most
instruments have higher resolution than accuracy.
I'm surprised you way what you said.
Also, I have not heard of a thermocouple that
goes from 0 to 150 deg C but is plus/minus 0.4
deg C. That's 0.3% accuracy. My old Radio Shack
one circa 1975 was like that, which is why it
displayed only 0.5 deg C increments. I doubt any
modern laboratory grade electronic instrument
would is that inaccurate. Here are the specs for my Omega HH12B:
Measurement Range: -200 to 1372°C (-328 to
1999°F) Accuracy (Type K Chromium-Alum): ± (0.1%
rdg +1°C) on -60 to 1372°C ± (0.1% rdg +2°C) on
-60 to -200°C ± (0.1% rdg +2°F) on -76 to 1999°F
± (0.1% rdg +4°F) on -76 to -328°F
<http://www.omega.com/ppt/pptsc.asp?ref=HH11B>http://www.omega.com/ppt/pptsc.asp?ref=HH11B
That's 0.1%, for an instrument costing $74. It
has a gigantic range, but anyway it is 0.1%.
Apples and Oranges. Sure, it might be possible to
calibrate the thing. Galantini mentioned no calibration.
Now, I didn't check something. There is a
high-precision probe, but Galantini has not specified it.
It does have an accuracy of +/- 0.05 C.
However, Galantini, in his mail to Krivit, said
he used "testo 176 H2" That's a 4-channel data
logger for temperature and humidity. Accuracy,
+/- 0.4 C. (Resolution 0.1 C). But those are the probes that come with it.
I have some probes for my LabJack. I think I
bought the cheap probes, they are +/- 1 C. The
more expensive probes are +/- 0.4 C. Apparently
that's some kind of common standard accuracy....
Resolution is not a probe characteristic, this is
an analog device. The cheaper probe provides a
voltage, 10 mv/degree K. The higher accuracy
probe provides about 18 mv per degree K. The
resolution is the resolution of the voltmeter,
and don't remember how that works out, with the
A/D converters in the LabJack....
This isn't about percentage accuracy. It's about absolute temperature accuracy.
