KETOTEK Digital pH & TDS Meters Water Quality Test Kit, pH Pen Tester TDS PPM Meter 2 in 1 Kit with 0~16.00ph and 0~9999ppm Measure Range for Hydroponic, Aquarium, Drinking Water, RO System, Pool

I didn't have to calibrate as mine came just perfect it seems out of box. Tested using known water amounts for both PH and TDS. I have been using it for about a month now on aquarium water and so far both have been working with no issues. PH is always around 7.1 to 7.25 which is where it was using API test kit or test strips. TDS slowly goes up over the course of a week until water change, then back down slightly and repeat.If yours comes calibrated or you can get it calibrated using the power (if it comes with meters, read sometimes it is missing) then these are definitely worth the money.

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Accuracy seems to be good but had to buy separate PH test solutions. The PH tester was missing one of the solution packets and was OBVIOUSLY a return from some other buyer. There was water in the PH test unit on arrival. The TDS meter had no calibration or test solutions.This is the problem with Amazon products these days. If a customer returns an item, Amazon just puts it back on the shelf and sends the same DEFECTIVE item out to the next person that orders that item. Come on Amazon...how many times does an item need to be returned before you take it off the shelf? This crappy cycle of having to return something to Amazon has led me to believe that if I want a complete and functional product the first time I order, I need to order it from a reliable source (like directly from the manufacturer.) I don’t buy as much stuff from Amazon anymore because 70% of the time products are broken, missing parts or not fully functional. You are losing my confidence and purchasing dollars, Amazon, and I’ll be looking elsewhere for items I need to work the 1st time I use it. Dang Amazon. Get your crap together. It’s really about customer service from FRONT TO BACK! When I order something, I want it functional and complete when I receive it. NOT AFTER MULTIPLE RETURNS.ARE YOU LISTENING AMAZON???

I have been using these for a week now and they are very accurate and fast. A huge savings over name brand meters like Bluelab but less durable. If you are safe with you tools its a great buy. I will never buy anything else again. I tested it against calibrated meters when I first got it and it was dead on so I saved the calibration solution. If you grow any plant hydroponically, you need these meters. Find ppm and pH guides for the plant you specialize in and adjust accordingly to maximize growth.

2 1/2.. That's the rating. TDS meter works fine for the most part, from what I can tell it's pretty accurate, the pH meter is garbage, never fully settled down, at best was within .8 of actual pH.. After a week it stopped reading anywhere near correct, a 4.1 was reading at 10.2 and such.. Then it just stopped turning on.. So yeah.. Garbage. But they are easy to use and the TDS meter has a hold button so you don't have to leave it in the bucket or cup to read the results.

So yeah, these work perfectly. Double checked them with some other meters I have. For the price, these are amazing! If they last, then great! If they don't, they still paid for themselves at this price point. But so far so good! They don't really take that long to settle out after introduction to a fluid - maybe a minute at most. But that's about the same speed as my bluelab probe used to take.

TDS meter was half the correct value. I used a 1000 ppm calibration solution for two other meters to check (this meter does not even calibrate). Junk! Don’t waste your money. The ph meter worked well for a few weeks, even calibrated we’ll, then ended up pinned to 3.42. I’ve purchased several other brands of these meters and these are the worst.

To accurately measure the PH of your liquid you need to buy a pre-made solution of alkaline water made specifically to calibrate PH readers.The PPM meter works very well and requires no setting up! A+!