The HANNA HYGROCHECK® uses the advanced TFPC* sensing method to measure humidity and an integrated electronic circuit to perform all relative conversions. This method of Relative Humidity measurement assures a quick and accurate readings. With a complete measurement range of 10% to 90% RH and an accuracy of 3% across the entire range, HYGROCHECK® is the most complete and versatile pocket-sized Hygrometer available! Most hygrometers on the market are too large or heavy to be carried around with other instruments for on-the-spot testing. The pocket-sized HYGROCHECK® is only 180 x 30 x 15 mm ( 7.1 x 1.2 x 0.6 " ) and weighs just 62 grams ( 2.2 oz.) . This compact, rugged unit will slip right into your pocket to be carried anywhere! The housing is constructed of durable ABS material and the LCD is protected behind a transparent plastic cover. The LCD displays the RH reading which can be read from any angle. Also, a vented cap protects the sensor while allowing maximum airflow for fast response.