With a probe diameter of only 0.16 in., the HMP 42 is ideal for monitoring the dryness of structures during construction; after water damage; for spot-checking humidity and temperature inside walls, ducts or chambers, and under resilient floor, according to the manufacturer. The replaceable filter protects the sensor from dust and particles, ensuring reliable, accurate on-site measurements. The hand-held HMI 41 indicator features an easy-to-read, two-line LCD display with selectable metric or non-metric units. It is also designed to calculate dewpoint and wetbulb temperatures, absolute humidity, and mixing ratio.

— Vaisala

Woburn, MA