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Tests
run: When researching this product, I found that
the specifications listed on the package, in the online
instruction manual, and on La Crosses site differed.
Which specifications are correct? One way to find
out. I put a WS-9400U in our Tenney Jr. thermal test
chamber, allowing me to run it through a range of
temperatures under controlled conditions. This
chamber lets me control temperature, but not
humidity. The readings on the WS-9400U were compared
to two lab thermistor thermometers, a Cole Parmer and a
Digi-sense. With these two lab thermometers, chamber
temperature can be determined to an accuracy of about .25
°F. In addition, I put
a Taylor 5522S Masons Hygrometer in the chamber to get a
reading on the humidity in the chamber. With the
circulation fan running in the chamber, the 5522S is
probably accurate to 2% humidity, at least until the wet
bulb wick starts to freeze at lower temperatures.
Test
results: I tested the WS-9400U at 6 test points, 4 to
determine accuracy at high, medium, low and very low, and
two to determine the range capability:
| Chamber
Temp & Humidity |
WS-9400U
readings |
| Temperature
|
Humidity |
Temperature |
Humidity |
| 101 °F
+/-.25 °F
|
|
OFL |
|
| 99.5 °F
+/-.25 °F |
44 % |
99.3 °F
|
44% |
| 71.8 °F
+/-.25 °F |
23 % |
71.7 °F
|
25 % |
| 39.5 °F
+/-.25 °F |
44 % |
39.5 °F
|
39 % |
| -8.3 °F
+/-.25 °F |
|
-7.8 °F
|
42 % |
| -11 °F
+/-.25 °F |
|
OFL |
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First the
disclaimers: I tested one unit chosen at random, brand
new, with fresh batteries. There will be unit to
unit variation, and performance may vary as the unit, and
batteries age, so your results may vary some.
Conclusion:
First, the operating range of this unit is -9.9
°F to 99.9
°F, as listed on the
package. I could not verify humidity range as my
chamber doesn't control humidity. This unit
performed better than I expected. Temperature
readings were within the accuracy limits of my lab
thermometers at all but the lowest reading, which was
still well within +/- 1 °F. Although this test
wasn't meant to test the accuracy of the hygrometer
readings over a broad range, or to better than a few
percent accuracy, the readings obtained indicate that the
hygrometer appears to be reasonably accurate for an
inexpensive unit, within normal operating range.
Personally, I wouldn't expect better than +/- 5% accuracy
from a low priced electronic hygrometer, even less as
temperature and humidity vary from normal room values.
Marty
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