BLUE lab PH meter/doser expected accuracy over time.

I'll usually check my guardian's probe in pH 7 calibration buffer every 2-3 weeks and recalibrate as necessary. Those pH probes do not last forever, they aren't designed to, and you can expect more drift the more use it gets. Blue Labs is fairly generous with their 6 month limited warranty. How long should they last? Depends on how you use it but at most a few years? Stretch out their life by cleaning before testing and/or recalibration and storing the tip in a 3-4 M KCl solution as much as possible. Not very practical with a doser I know, and I tend to leave mine in nutrient solution as well, but I have noticed less drift after storing it in KCl for a couple days, then at least 12-24 hours every week or so (easier for me since it's not on a doser). Replace the KCl storage solution occasionally as it will concentrate via evaporation if left out, and get contaminated by whatever is on the probe. Good info to follow here: https://support.bluelab.com/hc/en-us/articles/115002306603-what-is-kcl-storage-solution- "For this reason, when you hydrate or store your pH probe in our KCl solution, this helps to re-vitalise the KCl reference solution that is inside your pH probe. This is because some of the gel that inside your pH probe can flush out during use - if this happens in storage however, it means that fresh new KCl solution (from your storage cap of your pH probe) will then replace the solution that has flushed out of the probe. This means that the probe is almost 're-vitalised' while it is stored in the KCl solution." The connector and signaling on that probe is pretty standard and you can find cheaper 3rd party probes that will work with the Bluelab just fine. However, they will probably start drifting just as fast, if not faster than a bluelab probe if you don't use a KCL solution. Hope that helps.

I calibrate every 30days when the lights on the bluelab start blink and it's always just +-0.1 drift...so still very accurate after 30days I doublecheck PH/EC with milwakee instruments