HM Digital PH-200 Waterproof pH Meter, 0-14.00 pH Range, 0.01 pH Resolution, +/- 0.02 pH Readout Accuracy

FWIW, I'm writing the review from the POV of a spa user. You can use this tester for your pool, salt water aquarium or your hydroponic planter. My supposition is, you're looking at this item because you have needs above and beyond test kits or simple test strips. With this pH meter (potential of hydrogen), you'll be able to quickly tell what your water's pH is. HM also has a total dissolved solid (TDS) meter, the COM-100, which I've had for about a week and absolutely love.The unit is waterproof, light weight, a bit smaller than the size of a small "C" cell flashlight or about the size of a large cigar. It's easy to use, easy to maintain, has a small form factor for storage purposes and once calibrated, I feel it's an accurate piece of test equipment that gives you the feeling of having control over your spa tub water chemistry. The unit comes from the distributor pre-calibrated. Batteries are included. A cautionary warning note, the sensor periodically needs to be replaced. The replacement sensor number is: SP-P2. Replacement is a simple process of remove, replace and calibrate. Delivered, the sensor runs about $45.00.Knowing the pH of your water is an important aspect of monitoring spa water chemistry. Without a pH meter of this kind, one won't have a dependable clue what their pH level is. Using test strips or a test kit, my experience, readings can easily be off by up to 1.1 pH. Having your pH out of whack can cause you to have the condition of your water being too acidic, which can damage your heater element as well as low pH can be hard on eyes and skin. If the water is too base, you'll have to deal with calcification/scaling/cloudy water problems which is hard on the tub, jets and plain yucky to get in. The alternative to this meter, test strips or test kits is having to take the time and regularly drop in to your local pool/spa supply house with water sample in hand, where they're going want you to spend more money. And I hate spending money on chemicals I might not need. This all so I feel good about getting my water tested for free. With this tester, that's no longer an issue. And If you're a bit geeky, enjoy the feel of accurate test data and like the peace of mind created knowing you have control over your water's chemistry, after using this tester a few times, you'll feel confident that you're finally in control of your water's pH reading.Yes, in my opinion, the PH-200 is a bit expensive but if you have the extra green, for the peace of mind and control over your water chemistry this tester gives you, you'll quickly come to the same conclusion I came to; money well spent. Why? Because this tester is da bomb.Note 1. Be sure to buy some calibration solution so you know your reading is accurate due to proper calibration. Calibration is simple. Holding the middle button in for a few seconds puts the unit in calibration mode. Place the meter in the calibration fluid and then fine tune the reading displayed in the LCD using the up/down arrows. In this case, for spa water, I use 7.0 pH calibration fluid. You want to use a calibration fluid that's close to your expected needs: 4.00, 7.00 or 10.00 pH. In the case of this tester, calibration is no more difficult than using a television remote control.Note 2. Amazon has calibration packets for sale and with distilled water from the grocery store, you can mix up your own calibration fluid. FYI, you will need to have something like a 100ml graduated cylinder on hand to accurately measure the amount of distilled water you'll need when you mix up a batch of calibration fluid. Also needed, is some "electrode storage solution" to keep the sensor bulb wet. No big deal to use. Put a half dozen drops of fluid in the protective cap that covers the sensor, place the cap on the tester like a pen and you're good as long as the tester is stored standing upright to keep the fluid inside the cap. This is a very sensitive measuring device. This extra effort is not as big of a deal as I make it out to be. Once you do the first time, you're good. And if you care about decent testing gear, you won't mind this bit of extra effort and you'll be glad you got one of these pH testers.Hope the above helps.

I assume that most of the folks who have broken this quality probe or complained about how fragile it is have never used a quality/accurate PH meter before. The nature of the beast requires that the sensor be made the way this one is, and also that it remain wet with a storage solution at ALL TIMES! There is no gray area here folks! If you fail to rinse the end of the probe off with a spray bottle of distilled water after each use and then store it in the special reservoir cap with the sponge to hold the storage fluid up against the glass/gel sensor, YOU ARE ASKING FOR TROUBLE!The original unit I bought (Not from Amazon) arrived dry as a bone with the storage solution evaporated. I returned it for a refund and purchased the meter from another dealer who took better care of his stock. If your meter arrives dried out, I would suggest doing the same thing. Although the sensor can sometimes be rehydrated, I would be dubious as to the accuracy and prefer to get a replacement that was stored properly and/or didn't sit on a dealer's shelf for an eternity.In terms of the fragility of the glass sensor itself... The sensor end of the probe has a three sided housing that is designed to extend out beyond the actual glass sensor bead and shield it from impact from the sides, but obviously, if you manhandle the thing like a Gorilla and carelessly dunk it into a glass beaker or other container, there is a good chance that you are going to bring the sensor bead straight down onto the rim of the container or something and crack or shatter the sensor! DUH!! This thing is definitely not IDIOT PROOF, so idiots should probably look for something else or have someone with better hand/eye coordination do their testing for them!I purchased my original PH-200 well over two years ago and use it several times a day in my hydroponic garden. NEVER broke a sensor, never had one dry out, never had a problem with calibration, never had a problem with the device in any way! I like this brand and this model so much, I just bought another one here on Amazon because my original is getting close to needing a sensor replacement, and I had a gift card here and figured it would make sense to just buy an entire new unit for now and a new sensor for the original later!The auto calibration is GREAT! Buy yourself some calibration reference solution of 4.0 and 7.0 PH and READ THE INSTRUCTIONS ON THE LABEL ON HOW TO CALIBRATE the device. Unlike other meters in this general price range, there is no calibration screw to turn, no hassles at all! Just hold the CALIBRATE button down while the probe is immersed in the "quality" reference solution of your choice, and wait till the display reads "END". Takes about 5 seconds from start to finish after letting the sensor sit in the reference solution for a FULL MINUTE before hitting the button!DON'T DO WHAT MOST OF THE 1 AND 2 STAR REVIEWERS HERE DID AND CONTAMINATE THE CALIBRATION REFERENCE SOLUTION, AND THEN WHINE ABOUT THE UNIT FAILING TO CALIBRATE PROPERLY!Some lab guys calibrate before every test, and with this model, it is so easy to do, it really can be done in less than 5 seconds by pushing a button and waiting for the probe to self calibrate to the solution it is sitting in. It uses its PH measuring ability to identify the PH of the base solution you are using and calibrate accordingly. (7.0 or 4.0) In terms of accuracy... Like one of the other owners said... This thing is almost as accurate as the $1500.00+ lab grade PH meters, which is definitely saying something!So... Like anything, the device is only as good as the person using it and most of the low review scores are testament to how NOT TO USE THIS DEVICE! If you treat your equipment like crap and don't like reading owners manuals then this probe is probably not for you. If on the other hand, you are looking for an excellent WATER PROOF probe made by a company well respected in the laboratory equipment industry, a model that is considered by those who should know to be one of the best PH probes you can buy, then look no further than the PH-200.And when your unit arrives... READ the manual, and use some COMMON SENSE in handling it and it should give you years of trouble free service!I would give this thing 10 stars if I could, it is that good!

The HM meter costs a bit more than the Hanna machine, but the difference is worth the cost and more.I bought the Hanna machine, but soon I accidentally immersed it beyond the maximum line, and the unit has never recovered. I took it apart and dried it under gentle heat and then soaked the sensor in pH 7.0 solution for days, but no good. It would not calibrate over the 4.0 to 7.0 range repeatedly.The HM meter is waterproof, very sturdy, and measures temperature as well as pH. Its readout goes to two decimals instead of one. The readings may vary within +- 0.02, but not beyond that. It is quite repeatable.Automatic calibration is a snap. If you read the instructions, you cannot fail.Conclusion: It is the most hardy, reliable, and useful of all the meters under $100.