The Beverage Doctor portable pen style pH meter is an excellent value, considering all of the features it comes with. It is very accurate with 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 its lifespan.
This particular design is very easy to calibrate. You insert the probe into the pH calibration solution closest to the pH of the sample you want to test and push the CAL button, it detects which solution value it is, and then auto calibrates in less than 5 seconds. 3-point calibration allows this unit to be calibrated at three different standard levels - 4.00, 6.86 or 9.18. These standards are included with the pH meter, and refill packs are also available.
The Beverage Doctor is a great device at an amazing price!