The Extech EC400 ExStik® features six units of measure, internal memory that stores up to 15 labeled readings for easy recall, adjustable conductivity to TDS ratio factor from 0.4 to 1.0, and self-calibration upon power up. The EC400 incorporates the latest microprocessor chip technology and patented sensor technology to enable the simultaneous measurement of conductivity, TDS, salinity, and temperature. With the touch of a button the EC400 allows you the flexibility of interchangeable cell constants and has made the job of testing fast, accurate, and repeatable.