I had one that was always off by about 15-18%. I eventually replaced it becuase it didn't have a calibration button. Not sure if it would have stayed accurate or not; I just got tired of doing the math everytime I checked the rh!
both of mine have a calibration button. Once it's in the container with damp salt overnight, I just pressed it and it went to 70RH. Every time I test now, it's dead on.
Make sure you leave it in there with the salt completely sealed for at least 8-10 hours. I like to go 24 hours just to be sure. I usually hit the calibrate at around 10 hours and see if it stays for the 24.
Mine took around 3 tries.
Look at the calibration knob. Find the mark on it, and place it center of the calibration span.
Right when you put it into a SMALL ziplock baggie with half shot glass of salt ( beach sand wet no more) hit the reset button, wait til reading goes to Celsius and change to Fahrenheit if desired. Blow some air into the bag and zip it closed. Let sit AT LEAST 6 Hours at 68 to 70 deg F.
If its way off ( +/- 5% ) at 6 hours. Start over until its its reading within 5% of 75 Rh.
Again it took me three tries but now its dead on.
Make sure you leave it in there with the salt completely sealed for at least 8-10 hours. I like to go 24 hours just to be sure. I usually hit the calibrate at around 10 hours and see if it stays for the 24.
this is what i do but on a longer time frame. 24 hours hit the button, 24 hours to see if it sticks.
Just re calibrated all 4 of mine for the season change here in pa. About the fifth year I've done this, I've learned a few things. The mixture of salt and water to get the wet sand texture is very important. Distilled is a must, tell me your used distilled water? Last, for even my expensive meters, I have to have very small air pockets between the salt and meter in a sealed bag for it to be at 75 in even 12 hours. Sorry but I think you his saying 6 or 8 hours are nuts. Give it 24 hours and check it. Calibrate, if needed, ONLY after 24 hours in that salt calibration bag.
Just re calibrated all 4 of mine for the season change here in pa. About the fifth year I've done this, I've learned a few things. The mixture of salt and water to get the wet sand texture is very important. Distilled is a must, tell me your used distilled water? Last, for even my expensive meters, I have to have very small air pockets between the salt and meter in a sealed bag for it to be at 75 in even 12 hours. Sorry but I think you his saying 6 or 8 hours are nuts. Give it 24 hours and check it. Calibrate, if needed, ONLY after 24 hours in that salt calibration bag.
All I can tell you is no. Simple tap water. Have done it forever this way. And they are tested against the boveda 65% bags. So nuts maybe. Wrong doubtful. the water should be clean of course but that meter cares not if its distilled or not. And thus the small bag. Less rh to be stabilized in less oxygen in a small confined place, with a salt catalyst. Not a gallon bag. A simple sandwich will suffice. The amount of moisture in the surrounding air, at the meter, should be somewhere near 75rh even after only 6 to 8 hours. Laws of physics and chem 101. Rocket science its not. . Now add more oxygen you certainly need more time to stabilize the environment.
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