wrote in message
oups.com...
This is getting, confusing, complex and interesting!

In the same line as the Omega hint, and in the same cole palmer
catalog, I saw a Digi-sense Digital Handheld thermistor thermometer,
which has range of -40 to +125 Degree C and claims accuracy of +- 0.2
Degree C. Also offers an optional probe. Now is there any fine print
here?


I looked at the Cole-Parmer web site and tried to find the specific unit you
saw. I'm looking at their model 93210-00 thermistor thermometer. And there
is fine print.
If you took the time to download and read the instruction manual for that
model, you would see that it uses a YSI 400 series calibrated thermistor.
These thermistors are manufactured and specified to very close tolerances,
and can be used to good advantage in temperature measuring equipment. The
model 93210-00 thermometer is specified to have an accuracy specification of
+/- 0.2 deg C, but look at the specs a bit further. This accuracy is only
valid over the temperature range of 18 to 28 deg C. The "useful range", or
the range of temps that are deemed to be "in the ballpark", is a bit larger
at 0 to 40 deg C. Everything else is meaningless.
This same method of specification of themometers applies to most other
consumer-level (cheap) instruments. You have to read the complete spec..
not just the one that the marketing folks use to catch your eye.


so what I mean is, Can he use this 30$ Digi-sense thermometer at the
site and just take a sample and note it and claim that AT THAT POINT ON
EARTH AT THAT TIME the temperature was X degree C +- 0.2 deg C? or it
just dosen't work like this?


I couldn't find any of the Cole-Parmer models for $30 US... Which model
did you see for that price?


But I shall, at least in my spare time and slowly, wish to interface
and calibrate the sensor, because he takes PDA computer, and it has a
RS 232 port, and I'd love it if he just pressed a button and the
temperature was directly logged with the time and the GPS position (yes
the GPS is fairly inaccurate!)

I did see a model EW-93210-50 logging thermometer that boasts much better
accuracy, but it's also twice the price of the other unit. It offers you an
RS-232 port for connection to your laptop or handheld computer. These units
can offer the higher accuracy because of the tightly specified thermistors
used in the probes, and by use of a microprocessor-based measuring system.
The processor uses a lookup table that was created at the time of
calibration to compare the thermistor reading to the table of temperature
values. The temperature from the lookup table is the value displayed. When
these units are calibrated, they have to be calibrated as a probe-instrument
set. In order to maintain the stated accuracy, they have to be used as a
set.


It also occurs to me that I need to better understand this "temeprature"
term!

I'm not sure that "temperature" is your problem. I think you might need to
understand how to read and interpret manufacturers specs, which should be a
required course toward an engineering degree. {:) Just be sure that you
look at the complete spec before you buy (or recommend) an instrument.

Cheers!!!
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!