The Beverage Doctor portable pen style pH meter is an excellent value. It has a resolution of 0.01 pH. It is entirely waterproof, made of high quality components and includes automatic temperature compensation (ATC). The probe is designed to be easily and affordably replaced when needed. The cap seals perfectly over the probe to prevent it from drying out and decreasing lifespan.
This unit features three point calibration. To calibrate: insert the probe into the pH calibration solution closest to the pH of the sample you want to test and push the CAL button. The meter will detect the solution value and then auto calibrate it in less than 5 seconds.
A great device at an amazing price!