....are you looking for a pH meter, for testing liquids, or a pH probe, for testing in-pot soil/soilless mediums? The A8 in not for liquids,... I've used the A8 for a few years now, and it's been a valuable tool,.. for what it is, +/-0.2 pH is good enough to see what in-pot pH is,... but it needs to be used correctly! Dry or really soggy soil will give off readings I find,... also, don't test immediately after you have added nutrients or anything that may alter pH temporarily, until the soil has had a chance to react and stabilize,.... the probe has to sit in there for a couple minutes to stabilize,... bi-metal tip needs to be very clean and buffed out every time after storing, wiped clean between pot-to-pot uses, as any tarnishing/corrosion of the tip metals will mess with accuracy as well,...
... which model of BL pen is it?
Did you get storage solution and calibration standards for it as well? 7.0 and 4.0 are best,...
... having both of these on hand will help prevent big ph drifts in your pots,... adjusting your nutes before going in, and monitoring the in-pot pH regularly will all go a longs ways toward preventing this!