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When I first used this meter I of course calibrated it. It held the calibration for about a week then the readings went wild...oh no. So, I calibrated it again and it has been consistent ever since. I routinely verify its reading with another (way more expensive) meter and some paper pH test strips and this YINMIK is spot on. I like it especially for the price. It is my 'daily driver'.

I’m actually surprised at how well this ph meter works. I owned for 6 months now and started to have doubts about its accuracy. I purchased a more expensive $85 meter and after calibrating it I tested both meters in water.To my surprise Both came out with the same reading. I have only calibrated this meter once when I first got it. Very nice to see a $20 meter holds up to a much more expensive one. This only complaint I have about this meter is lack of the backlight staying on while I measure the water. For the price this is an extremely well made meter that holds calibration well over time. I would definitely recommend this meter

Works good make sure you follow the instructions for the calibration solution and calibrate every few weeks for safe measure only problem I have is it jumps all over the place once you pull it out of the water or solution your testing even after rinse and drying it seldom sits on 0.0 like it should but as soon as I put it in the water I'm testing or the calibration solution it reads perfect I'd say good buy for the cost when comparing to some of the other stuff

Item was delivered on time. One of the nicest meters I have ever bought. The display screen is very easy to read and very bright. Simple instructions. It even came with extra ph solutions. It seems to be built very solid and the size is perfect. I didn't even calibrate it before first use. I am going to say that it is a quality meter with a low price. Will buy again.

Works great

Probe is reading pH's of buffer solutions almost 1.01 whole point lower than each pH packaging implies should be (4.00 solution offers 3.01 reading, 7.00 solution offers 6.01 reading, and the 10.10 offers 9.11 reading). pH of buffer solution was tested w/ pH strips to ensure the solution values were accurate prior to attempting calibration, and of course mixed the powders with 250ml of distilled water as directed. The whole point of calibration is being able to adjust output readings based on input values so that output is setting out the correct measurements. This pH probe is useless as is unless I want to add .99 to each and every measurement I take, though I have no confidence in the product anymore anyway. Also, the cap contained a sponge that instructions indicated was supposed to be moist. It wasn't, and there was some kind of unknown clear slime on the inside of the cap that I'm sure the probe had contact with or that somehow leaked from the probe. Either way, I'm not happy. Product packaging instructions indicated it could be returned or replaced within 12 months, but Amazon's stated option is only 30 days. We're about 15 days past that, so I guess I'm just ripped off. Sometimes it reads straight 0000 across unless you kind of knock it against the glass, insinuating that there is a faulty connection or chip in there somewhere (despite unscrewing and ensuring everything is connected properly). *Editing to add* This product did not come with the calibration solution for EC/TDS settings either, nor the storage solution (I read in a review that product finally calibrated correctly after being submerged in SSolution for 24 hours, and given the cap sponge was so dry, thought I would try BUT I don't even have that option here. Did add a couple of drops of distilled water to cap sponge as per instructions, but it does not seem to matter much) And, only 2 packets each of 4-7-10.01 pH buffer solutions, which is also unhelpful beyond 2 calibrations, IF they had worked in the first place.

Works as expected

Ok let me start by saying I was skeptical. So skeptical I bought a bluelab which is $100 + pen (which I initially didn't want to purchase, but did) Now yinmk says out of the box it's pre calibrated. It was off from factory so I would suggest calibrating when you get it! Now I calibrated my blue labs because both read 1.0 off which is a huge difference a make or break when it comes to a grow. After calibrating the blue lab in bluelab solution I retested side by and the yinmik was .30 off which wasn't terrible but also not properly calibrated. I also tested in 7.0 solution, and 4.0 solution and yes .30 off in both solutions. So I calibrated in 7.0 and 4.0 and then went side by side and both seem to read exactly the same now. The provide a powder mix solution but I'd buy a better grade liquid solution to calibrate with. Blue labs gives a checkmark when you're calibrated and checkmark leaves when it's time to recalibrate. I've only used for 2 weeks so far its very good for the price. Pros to the yinmk 1. Extra batteries 2. Calibration Solution powders 3. Feels good quality/probe looks good too 4. Easy to use and can compare to a big dollar ph pen. Cons. 1. Claims calibrated but off 2. It's a little over worked, bottom unscrews, top unscrews, just more to not have properly positioned right. 3. It doesn't tell you that it's calibrated or when to re calibrate like a bluelab. Update: broke, water got inside somehow and stopped reading ph.

Followed instructions exactly. Tried 20 times. You’re supposed to turn on unit, place it in 7 ph calibration solution, let it settle and then hold cal button for 5 seconds. That’s supposed to enter calibration mode. Tried holding everywhere from 2 seconds to 30 seconds. No matter what it won’t calibrate making it useless. Unless the seller can fix this I’ll be sending it back. Waste of money and most importantly time.