I have an Apera Ph tester (GS4). My usage is a bit erratic. Each time I change a nutrient or soil recipe or change the brand of something in them, I test. I test occasionally even if I didn’t change anything, but I don’t test every time I water.
Anyway, I was looking in the manual for something and came across the notice that probes only last about 18 months and I should replace them on that cycle. The probe is replaceable, but the replacements are expensive. It’s probably worthwhile to just replace the entire tester if the probe is bad. I haven’t done this and it’s been well over 18 months.
Do I really need to change it? How will I know that it really needs changed? It seems to work fine still. It calibrates painlessly and the results of the tests are about what I expect. I have the feeling Apera is just trying to boost sales. It would be nice to know the symptoms of needing a change rather than an expected service life.
My current probe is over two years old and going strong, I calibrate once a month, BUT, I’m checking it each watering because I feed a set amount and I know the EC and PH of my feeds, the tester is just another verification that the mix and the tester are the same each time. My meter is 5 yrs old and this is my second probe.
From my experience working in a lab here were some signs it was that time.
pH readings totally off expected values. This is particularly relevant when calibrating with fresh/good pH buffers/standards. Example, when typically a calibration only required an adjustment of 0.1 units now requires a full 1.0 adjustment.
pH meter takes much longer to settle on a value than before.
You’ve already touched on this but unexpected readings from typical pH tests.
Maintenance and proper storage of the pH probe (e.g. storage solution per manufactures guidance) are key and trump any predetermined lifespan estimate.
