The General Tools REF114ATC 0-32% Hand Held Brix Refractometer with Automatic Temperature Compensation specifically measures Brix (°Bx) levels in liquid, or the mass ratio of dissolved sugar to water in a liquid. The Refractometer also has an ATC function, or Automatic Temperature Compensation. Meters and controllers with automatic temperature compensation (ATC) receive a continuous signal from a temperature element and automatically correct the pH value based on the temperature of the solution..