CoZroom Digital Water Tester Set, Aquarium PH, TDS Meter and LCD Thermometer with PPM Meter Pen Home Improvement Set Tools Digital PH meter in a pen style will be an ideal and perfect instrument for testing and your aquarium. Characteristics of this set: Excellent meter, very accurate and durable. Measuring PH Range: 0.0 - 14.0 PH. Resolution: 0.1 PH. Designed with LCD display for easy reading. Thermometer with suction cup and easy to installation; Temperature readings to within 0.1 degree Easy and simple to use. To turn on/off by press and hold the power (pwr) button for 5 seconds.