Hanna pH/Temperature Waterproof Pen (pHep4 Meter) HANNA WATERPROOF PENS Hanna Instruments offer the most advanced pens in the market today. The pHep4 pH/Temperature waterproof pen has a .01 ph resolution. The Dist5 EC/TDS pen is unmatched in EC/TDS/Temperature measurement. The Combo pH/EC/TDS/Temperature pen offers highly advanced accuracy with a single tester. All Hanna Instruments pens offer replaceable graphite electrode, temperature in degrees C or degrees F, automatic temperature compensation with adjustable battery level indicator, stability indicator, automatic shut-off and automatic calibration all in a floating waterproof casing. MSRP: $102.95