I used to by the cheap HM Digital pH pens. Finally said ftw and bought a Bluelab combo meter. Gives super fast readings, very reliable, and even reminds you monthly to calibrate, even though it’s never been off in the 2 years I’ve had it.
https://www.amazon.com/Bluelab-7164...549071281&sr=8-1&keywords=bluelab+combo+meter
https://www.amazon.com/Bluelab-7164...549071281&sr=8-1&keywords=bluelab+combo+meter