2 months ago
#12913 Quote
The easiest way is to use a saturated salt solution.  see


for guidance.

As an example to check the RH accuracy of a A-1 probe drill a 3/16" hole into the side of a taller (about 4 " tall) Tupperware container about 1" from the top, fill the container with 1" of distilled water, add table salt (aka NaCl aka sodium chloride) salt and stir until added salt no longer dissolves into the solution indicating it is "saturated".  Seal the container and insert the A-1 probe tip into the container such that the probe tip will be exposed to the air above the saturated salt solution.  Wait until the RH has stabilized.  Make sure the Tupperware container is in a temperature stable environment, a large cooler can help with this.  

If it touches the salt solution immediately unplug it and rinse thoroughly with warm water, blow dry with compressed air and let dry for 24 hours before using it.