pH PenPlus
From Bluelab, the pH PenPlus is a compact and handheld digital measurement tool for nutrient solution pH and temperature, with a double-junction and screw-cap replaceable probe design for easy replacement and long-term use. Additionally, the pH PenPlus can read temperature in °C or °F, features an auto-off function to conserve battery, and holds a IP68 dustproof and waterproof rating.
