This sensor can measure the static pH values of common liquids. -Durable Electrode -Designed for Long Life -Sealed Reference System -Gel Fill It also measures changing values in titrations or experiments. The sensor gives a fast response across the full pH range and can be calibrated with any standard buffer solution. Its sealed reference system and gel fill make it easy to use and maintain. With an epoxy body, it's a durable electrode to use in the laboratory and in the field. Insert the sensor into a buffer of your choice, hold the push button for three seconds, and the reading will calibrate to that buffer's pH. It supports experiments lasting between one second and 31 days.