Any pH meter that costs less than $300 is a toy.
There was a time, not that long ago, when this was true but it isn't any more. There are a couple of meters out there at around $150 that are pretty good - certainly good enough for brewing.
Honestly, everyday use field testers have electrodes that cost $300. That's not lab quality I'm talking about, that's what your lawncare company is carrying around.
There are plenty of lab quality electrodes that cost around $300 (e.g. the Hach Platinum series that I use for all my lab work: $329 - lasts over 5 years, you cannot foul the junction, stable as a rock) and some field/factory electrodes that cost more. And there are lab electrodes that cost more too. Higher $ do not guarantee better accuracy and are usually associated with additional toughness for rough handling circumstances, signal conditioning in the electrode itself (simple serial digital interface to the 'meter') etc.
Ballpark is too strong a word. I thought it would be neat to carry around one of those pen types to ballpark tanks rather than run samples back to the lab- results are shockingly unreliable and they do not have adequate calibration checks.
You can obtain reliable readings with a pocket meter for half of $300 but you have to obtain a good meter, calibrate it properly and check on its stability. There are notes on how to do all that in a Sticky under Brewing Science. If a meter is given a proper cal and if it repeatedly reads the correct pH in a buffer over an extended period of time (your mission time) then it is accurate and you don't care how much it costs. As a pH meter is calibrated before use it is dead nuts on at the completion of calibration provided you wait long enough that the electrode is at equilibrium. This often takes a few minutes, even with a new electrode, and failure to wait long enough or to let the meter decide when to take the cal reading rather than making that decision your self based on observation is probably the biggest cause of poor pH readings with equipment which can potentially give much better results.
You won't know when it's lying to you,
You will if you do a cal check (not a full calibration) from time to time. But you will have verified that your meter is stable with a stability test before you go into the field with it and thus be confident in what it will do. It is, nevertheless, wise to trust but verify!
I bet a random list of feasible beer pH's would match a $20 pH meters accuracy. Paper strips is the best you can do on a budget.
At the $20 price point I agree but you don't need to spend $300 or more (who needs an RS232 interface, a memory which records the time, date, calibration parameters, mV and operator's name for each of 2000 readings?).
Also, a 1 point calibration is useless.
One point calibrations are fine if you are taking measurements near the pH of the buffer you used for the calibration. In brewing we are working about half way between and so must have 2 point. Of the 3 $120 meters we have vetted here on HBD (Hach, Milwaukee, Omega) all are capable of 2 (and 3 but 3 point cal doesn't buy you anything) calibration.
calibration doesn't make something accurate.
Calibration does make something accurate if the something is stable. If, IOW, a pH electrode reads 20 mV at 7.00 pH that can be calibrated out and the meter will be accurate 4 hour later if the electrode still reads 20 mV in 7.00 pH buffer. If it reads 30 mV the electrode has drifted. That is the problem with cheap meters. Their electrodes are not stable. State of the art with electronics today is such that the meter itself is not the problem.
Stick to papers for budget pH testing.
'Budget' hasn't been defined but if you can't afford $120 for a pH meter I always say forego 20 $6.00 pints at your local, use the money to buy a meter and brew an extra 20 pints over the course of the next couple of months. If you cannot do this don't use papers. They notoriously inaccurate. You would probably do better to rely on the predictions of one of the several available brewing calculators.
