HDE Digital pH Meter Tester This digital pen style pH meter is an ideal instrument for anywhere you may need to test pH levels. Excellent meter, very accurate and durable. Measuring pH Range: 0.0 - 14.0 pH. Resolution: 0.1 pH. Accuracy: 0.1 pH (20C), 0.2 pH. Operating Temperature: 0 - 50C (32 - 122F). Meter comes with protective plastic case and calibration screwdriver. Size: 6" x 1" x 5/8";