Jim Yanik wrote:
gregz wrote in

rg:

Spehro Pefhany wrote:
On Tue, 29 May 2012 11:36:59 -0400, the renowned "Johnny Appleseed"
wrote:

I have a digital thermometer like the one he

http://www.walmart.com/ip/Acurite-Wi...meter/16888921

The temperature the outdoor sensor reads is at least 3 degrees off
from what it should be. Is there any way to adjust the temperature
reading in these units? The instructions don't say anything about
this issue.

Thanks,
John

These type of things use a "precision" thermistor that is supposed to
be good to a degree or so against an internal fixed reference
resistor. There is no individual calibration. You could try to trim
the reference resistor, but personally I'd f'dget about it. 3 degrees
(F?) could be the difference between being in the sun and not, for
example.

What do you expect for $10?


Best regards,
Spehro Pefhany

I got two different devices with fairly constant 3 degree difference.
My one with wind gauge, I don't believe. I think it reads half. I'm
going to take it for a ride some day.
One transmitter failed after a few years. Bought replacement. I have
other cheap units go bad, but my current models are half decent.

Greg


My WalMart $10 Acurite wireless remote thermometer also seems to read about
that high.
it's on my covered,screened patio,out of direct sun,and sheltered.

FYI,real cal labs use a platinum platinum-rhodium resistance thermometer
with a correction chart(from NIST) for really precise temp calibrations.
We had a temp-controlled circulating mineral oil bath in which to put the
DUT and reference thermometer.
I used to do that in the USAF.(PMEL)


Oh, I remember PMEL. Had one on NASA site. I used to make do with what I
had, and accuracy necessity, in a research design, and repIr shop.

Greg