Hanna Instruments offers two instruments to meet water-testing requirements. The HI 991300C and HI 991301C provide the combination of pH, conductivity, total dissolved solids (TDS) and temperature requirements in degrees Fahrenheit or Celsius. With only two buttons, the user can select testing parameters, calibrate the sensor and change the TDS factor and temperature coefficient. The housing is waterproof and rated for IP 67 conditions, and the multi-functional industrial probe houses the pH and conductivity sensor, along with an integrated solid-state amplifier to eliminate noise and interference. Hanna Instruments, Card No. 287