Just test with 4 than rinse and dry the prob off and do the seven,no need to wait.If your positive your tap water is always the same you can just use that but I'm not to sure if it will be the same all the time.
If it's like my Bluelab pen, you drop it in the 7, wait until it settles at or near 7, then press calibrate. When it finishes that calibration, drop it in the 4 and wait until it settles at or near 4, then press calibrate. Bam, done.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.