I use a ph meter for plant nutrient solution. Previously, I had a couple of cheap China imports, which seemed reasonably accurate for a while, but don't last long. All ph probes degrade over time, so rather than keep buying cheap, I decided to get a more reliable one with a replaceable probe. This is quite expensive compared to some other brands with good reviews, say the Essentials PH Meter, and @ £29 the replacement probe is not much cheaper than buying a new Essentials meter. However, replacing just the probe reduces waste, and gives you options: there are 4 compatible probe types (all available on Amazon), which you can buy separately as replacements, or to measure different substances. The glass bulb is for liquids, the spear probe for solids, such as foods, soil, the flat probe for paper, cloth, skin etc. And you can buy an ORP (Oxygen Reduction Potential) probe to use with this meter, which tells you the "killing power" of your solution/water (sterilising or not, a simplification of complex subject). The life of the probe will depend on how often you use it, and how you treat it. The probe is supposed to last 12 - 24 months - it's CE rated for 6 months (for safe use), but that's NOT its life expectancy. It CAN be stored dry, without degrading it, according to instructions, but storing it dry will affect its sensitivity. So if you store it dry, for accuracy, you need to soak it in the provided solution before use. It can be stored in the soaking solution, but NOT in purified water. The kit comes with everything you need: soaking solution, 2 calibration solutions, batteries, lanyard (quite a long one), 2 containers for calibration, instruction manuals in English and German, as well as a laminated quick reference chart, all in a hard plastic case. The instructions are clear, easy to understand, and contain all relevant info. Instructions say not to use soaking/storage solutions from other companies, but as long as the same (potassium chloride or kcl @ 3 molar strength) and/or for the same type of ph meter, I don't see why. Will be ignoring that myself (no Apera replacements on Amazon, either). The calibration solutions will last quite a while, the soaking solution is enough to fill the cap to the mark about twice. 2 reviews for the replacement probe said the glass bulb was too exposed and breaks easily. I disagree - the bulb is inside and above the plastic rim, which does have gaps in the side, but doubt it would break if dropped on flat surface. IP67 means it's dust proof, and can be immersed in up to 1 m of water, or for up to 30 mins, depending on info source. It doesn't mean it's hermetically sealed, though. Overall, the meter seems robust, and looks like it will stand up well to any normal use. So far, would recommend, despite quite high price, as seems well worth it, all things considered. Just to add: been using this for a while now, and still very happy with it. Like the back-light feature, and it's very easy to calibrate.
