PH meter is useless, TDS meter seems ok
Reviewed in Canada on 3 July 2021
TL:DR; PH meter varies wildly and never settles on a reading. EC/TDS meter seems "good enough."
UPDATE JULY 15 2021:
PH meter has gone crazy, never settles to 0000 when turned on, readings in air are all over the place, 3.43 one second, 5.77 the next, 12.53 after that. 4.00PH Calibration solution reads anywhere from 2.75PH to 6.85, never settles on a number but gets NEAR to 4.00 just as the screen times out. Turning it back on right away it'll creep slowly up and down, around 0.5PH out depending on if it started high or low(IE 4.5PH if it started above 4, or 3.5PH if it started below). Calibrating with provided 4.00PH solution seems to work, until I remove it from said solution, at which point it goes crazy again. Already replaced the batteries, but tried brand new ones anyways, no difference.
Here's the deal for my order; PH meter instructions say to soak it in distilled water if it has been unused for longtime, i did so(3-4hrs). After this i tested some other distilled water(ph7, and i used fresh water and brand new solo cups every time in the following tests/calibrations). Reading showed 5.50 initially and dropped constantly for the next 5mins, I gave up on it at 3.27. Tested several times, roughly the same results(2.85, 3.76, 4.22, etc...) Calibrated using 6.86 powder dissolved in 250mls distilled water. Meter now reads 0.15 permanently (used to show 0000) and distilled water now reads 8.5 and climbing(+0.1 every 3-5secs) . Gave up after 5mins again, meter was at 13.29. Calibrated using 4ph powder in distilled water, tested in distilled water again. Initial reading was 3.25, rapidly climbed to 6.5, almost settled, then started falling. After 5mins reading was 1.29. Calibrated using 6.86, then 4.0, then 9.18 (still following instructions) and retested. Reading was 7.15 initially, after 2-3mins it actually SETTLED!! At 5.29. Tried again, this time it settled at 5.86 after 30-45seconds then started falling slowly. Sensor bead is full of liquid(water?), and there's a tiny white plug beside it in the bottom/sensor end of the device. I suspect this is supposed to be filled with liquid of a particular PH or with specific additives, and has actually been filled with whatever water was on hand in the "cheap knockoffs" factory my PH meter VERY obviously comes from. ALSO, there was some sorta white plastic sealant all over the area around the sensor, had a few gobs hanging out when i opened the cap for the first time. I VERY carefully used tweezers to pull off the gobs but left the rest alone.
EC meter: i made 4L of hydroponic solution using General Hydroponics Flora series nutes, following their growth charts for aggressive feeding, week 1, bloom. PPM @ 23°C showed 1226ppm. Charts say 1200, this is close enough for the girls I'm growing.
That's all, but since i have only had my order 6hrs I'll come back and update if the EC meter craps out in the next, say, 6-8mths. Stars given are average values, atm EC meter gets 4stars in everything, while the PH meter gets 1 for all.