Review on Accurate and Reliable VIVOSUN Digital PH Tester Pen for Water Testing by Paul Andrews

This helped me find the right pH for my plants. It seems well built. I really like how the display lights up on first use, although I wish it stayed lit because the first few seconds are never accurate, you have to let it calculate and set it to around 60 seconds. Pictured is my pen in my DIY solution vault after 24 hours. WARNING TO ALL NOOBS: Do not trust or test any of these products for water resistance. Don't throw them in the water. It is assumed that only the first 1-1.5 inches will ever get into the solution. This is indicated on the paper supplied with the product. To avoid contamination, do not test directly in your solution. To test, pour some of the solution into a small beaker. STORAGE: Store the product in the electrode solution after opening the pen. If you're not smart, buy a bottle of Revine's solution. If you're smart you can make your own: buy a 1lb bag of KCL, an AMIR portable scale, a couple of graduated pipettes and deionized water from the grocery store at Revain (I had a car that I had to run) . around to fill with fresh, filtered water). I tested distilled water versus reverse osmosis and the reverse osmosis water was closer to 7.0 so I used that for my solution. Then weigh and mix 7.45 g of KCL in 100 mL of neutral water to obtain a 4 molar (4 M) KCL solution. Boom. You now have a lifetime supply of storage solution. I found this with a quick google search (Omega Engineering pH Electrode PDF). Remove pen from solution, rinse with neutral water, place pen in small beaker with 1 inch (2.54 cm) of test solution, note value, rinse with neutral water, return pen to storage solution. I gave it four stars for several reasons: 1) "Very Accurate". This means it helps me get closer to my desired pH by improving accuracy in the 0.1 to 0.5 pH range. I don't trust the factory calibration because I've already used it with some deviations. I think as soon as you take the electrode out and use it on a water source you will affect its ability to test another solution. For analog chemical reagent tests, I used a general purpose whirlpool kit and a General Hydroponics reagent test. It outperforms the Whirlpool reagent kit many times over (since this reagent test only tests between 6.8 and 8.2) and the GH reagent kit with a pH range of 0.5-0.9. For example, GH showed 6.5 pH, actually 6.2 (with this pen). Then I adjusted the pH. GG showed 5.0. Actual result was 5.8 (with this pen) 2) "Cheap" - you can't find cheaper 3) It only includes 1 calibration test kit and no indication where to get more. I would pay $5-10 more to add a box of calibration pouches to my order. 4) The display backlight is off and there is no "light" button.