The Triplett PH185 is a replacement flat surface electrode for the PH180 PH Pen. The Triplett PH185 can be used to measure pH in liquids, semi-solids or any flat surface. Measurement range is from 0 to 14 pH with 0.01pH resolution. The Triplett PH185 features ATC (Automatic Temperature Control) that compensates for temperature changes. RENEW warning when the probe needs cleaning or replacement.