Extech EA11A-NIST with NIST Certificate:

Professional-grade pH meter with NIST-traceable calibration for accurate and reliable pH measurements. Features include:

NIST-traceable calibration certificate for laboratory-grade accuracy
Automatic temperature compensation for precise readings in varying temperatures
Large, easy-to-read LCD display with backlight for clear visibility
Waterproof and dustproof housing for durability in harsh environments
* Replaceable pH electrode for extended lifespan