Hanna InstrumentsHI98108 pHep + pH Tester with Automatic Temperature Compensation, 0.0 to 14.0 pH, +/-0.1 pH accuracy, 0.1 pH Resolution

I bought this unit having owned the red version without atc for two years. I am prone to dropping these in what I'm measuring so this is a backup but functions perfectly. They are durable little units. My original phep has been dropped in solution several times. I remove the batteries immediately and just let it dry out, after a day or two I calibrate it and it's back to normal. During one of the events I bought a much nicer hannah unit here http://www.amazon.com/gp/product/B003IKNJIE?psc=1&redirect=true&ref_=oh_aui_search_detailpageI've never been able to calibrate the unit even with the hanna brand reference solutions. This device has been much better to me.recommendations:Always store it with a little storage solution in the cap.If it starts being unpredictable and you haven't been using storage solution soak it in storage solution for a couple days.

Good meter but needs to be calibrated regularly. Get both calibration solutions if you but this.

I find that after calibration with both pH 7 and 4 buffers this meter holds the calibration for at least a week, so far. I am using this for aquarium and soil testing and find it very helpful and easy to use. I think it could be improved upon by making the cap water tight so you could keep the storage solution in it without spilling. Currently, I store it standing in a small beaker of the storage solution. I highly recommend this pH meter for anyone who is looking for one. Just remember, DO NOT TOUCH THE CLASS ELECTRODE. It is very fragile. If you must wipe it, use a wet tissue and do it lightly. The glass electrode functions by soaking it in a storage solution to cause a very thin layer to absorb water and swell. This gel, so to speak, is fragile. You may need to allow it to soak a day or two to obtain stable readings again.Here it is October 2013 and this pH meter is only 0.1 pH off at 7.01 standard. Easily calibrated and back in business.

Works great. Easy to calibrate

the instruments working well , so far so good.

Poor quality. In storage solution and it crystallized. Will not buy Hanna again

I use it daily, and it needs re-calibration daily. The pH 7.0 calibration point drifts, unlike the Hanna HI98128 that it replaced. The cal adjustments are via plastic-shaft screwdriver-adjust trim pots that are not likely to last from needing daily adjustment. The 7.0 cal trim pot adjusts the reading from pH 3.5 to pH 10.4, a tremendous range for a single turn, probably 270-degree, trim pot. It's understandably touchy which may be a large part of the stability problem. Yes - I store the meter and the cal solutions in a controlled temperature environment. I recommend buying a higher end pH meter,

Well calibrated!! Performs well!

great quality for price