Extech 445580 Humidity and Temperature Pen Sized Meter with Pocket Clip

A Gem in a Field of Cheap Toys
I want to preface this review with the caveat that in order to achieve accurate relative humidity readings, this psychrometer will require the use of a 33% and 75% calibration salt kit. While they cost as much as this meter, they at least ensure accuracy, which was NOT achieved through factory calibration. As shown in the review image, the RH% reading is not calibrated we’ll out of the box, but that can be expected as calibration can change in storage or shipping.I went through and returned several other psychrometers on Amazon before finally finding this one, which actually worked as described. The entire market is saturated with cheap Chinese clones where a company (sometimes reputable) slaps their name on, or changes the color of, the same generic Chinese psychrometer (often 12 degrees F or more off and unable to be calibrated). This meter, however, is unique in on the market and has the backing of the company that produced it.The calibration procedure with the Extech salt kit is easy. The meter is perfectly sized to fit within their calibration bottles and the directions are clear on how to calibrate both to 33% and 75% relative humidity.The construction of the meter exceed that of the competition as well. While It is still plastic, that plastic feels thicker and more solid than the other models on the market which feel like cheap toys. The meter reacts very quickly to changes in temperature and humidity, possibly sub-second, but does take a good 20 seconds or so to stabilize in a new environment.My goal for the meter was to establish as accurate a baseline reading for Temperature and Relative Humidity as possible for use in calibration many other sensors of varying makes and brands within my home automation system and I can gladly report that the goal has been achieved through this meter.

Easy to use, includes relative humidity, great for residential HVAC maintenance work.
No dislikes, great accuracy and easy to use and easy to read.

Accuracy
I purchased this as an inexpensive tool to have for checking clients humidity levels in businesses. I found myself questioning its accuracy. The tool does not adjust as quickly as expected from exterior reading to inside reading. I’ve used extract in the past and I thought I was getting extract quality. I should have purchased their more expensive unit that I deem reliable.

Celcius Degree Users FYI
The pen looks nice. I usually use °C and what bothered me is when I turn off the instrument an turn it on, it is in °F again.After reading the manual I realized there is a procedure to make °C permanent. That was a relieved.

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Needs to be calibrated for the humidity reading.The calibration bottle cost a bomb,much more than the device itself.DO NOT BUY.Amazon and the seller were kind enough to arrange for a promt refund.One should buy only the thermomter….