<font><font face="verdana,sans-serif">For those who want to read more about these instruments, I pulled this off an Amazon review of the Caliber III hygrometer<font>: S</font><br><br></font></font><br>I do environmental surveys as part of my professional work and use a
variety of expensive analog and digital instruments, thermometer wet/dry
bulb psychrometers, multi-hair recording hygrothermographs, some
instruments with NIST certification (but not mirror instruments). I've
bought several analog and digital hygrometers costing under $150.00
(including the Caliber III) to play with and check for use by my
daughters who humidify and dehumidify their living and storage spaces
for violins and violas. I give this little instrument 5 stars for being
accurate for its price - certainly accurate enough for musical
instrument storage, cigar humidors, and basic building environmental
monitoring. However, don't expect that "accurate" means what the
instrument displays is what the environment really is. And do not expect
these inexpensive instruments to all read the same. All the inexpensive
instruments I purchased and all my professional instruments costing
into the thousands do not give exactly the same readings when placed
together in a controlled climate chamber. Do not expect a lot of
precision in humidity measurement for a number of factors too
complicated to go into here but related to particles and various gaseous
molecules in the air. For most instruments costing under $150.00
reading, let's say, 50% RH, just believe the RH is in the range 46-54%.
For instruments up to $1,000, a 50% RH reading probably represents
actual RH of 48-52% RH. Do not expect more. One other thing you must
know about digital hygrometers, and this is critical to recognize, they
are fast and accurate (again within reason) and they quickly read their
local environments which includes your body heat, skin moisture, breath
moisture, and varying temperature and humidity in local air currents you
may not even feel. You are a walking cloud. Certainly don't hold one
and expect it to match another instrument sitting next to it on a shelf!
The heat of your hand warms the plastic case raising the temperature
reading and thus also drastically affecting RH. Don't even stand within
three feet of one and expect it to match the display of one four feet
from you. Also, this digital instrument and others like it will detect
and display numbers representing the real differences in the environment
that can exist just inches apart. That's why two of the same
instruments next to each other may not match - its not bad quality but
high sensitivity. This speed and accuracy of even inexpensive
hygrometers is probably the sole cause of people complaining about
"inaccuracy" of digital hygrometers and the frustration they experience.
For more information related to how difficult it is to really get
accurate RH readings and difficulty in calibration read reprinted
articles on the Veriteq website. If you want just "a little more
accuracy", you can get "a little more accuracy" by paying a few extra
hundred dollars, like over $500 for a Vaisala HM34. For the price, and
considering how nearly impossible it is to get a true measurement of RH,
maybe its good enough for you just to know, for example, "well, the RH
is somewhere between 50 and 60 according to this instrument." Even
knowing this a digital hygrometer's speed and sensitivity can still make
one feel frustrated.