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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.

Worked OK at first after calibrating it new out of the box.Reading seemed to vary about .05. 7.01 solution would drift from 7-7.5.Even immediately after first calibration.The powder calibration solutions are trash, take forever to dissolve, and require too much purified water, in my opinion.I used this meter for around 5-6 months and is already broken.I followed all instructions to a point, cleaned, and stored, exactly as described.Now, approximately 6 months later, whenever I use the meter, the PH reads an entire point high - 7.0 reads 8.0 - even immediately after a new calibration.I calibrated it several times, but whenever I would turn the unit off and then back on, would read 1 point higher than the actual solution ph.This has caused me issues and stress by putting my trust into a faulty piece of "technology" giving me FALSE READINGS!DO NOT BUY! Not just this brand, but every PH meter cheap or expensive that I have used has become inaccurate after 6 months.I am quite convinced these digital meters are a flawed ineffective and expensive technology to "read" PH. Now I am stuck with a broken piece of trash that I can't seem to return now. I will go back to using liquid or paper tests.

Seems to work well. During storage the bulb on the end needs to stay moist. I had mildew problems with mine. Otherwise it's ok. Nice it came with a few calibration packets to verify it's operation.

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 yinmk1. Extra batteries2. Calibration Solution powders3. Feels good quality/probe looks good too4. Easy to use and can compare to a big dollar ph pen.Cons.1. Claims calibrated but off2. 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.

This pen is very easy to setup. Comes with batteries ready to go. Comes with packets to balance the pen. You will need some distilled water to help calibrate. I recommend it. So far so good few years in.