Our refractometers measures dissolved solids (soluble solids) using the "critical angle" technique (an interface measurement of refractive index). This measurement technique is not sensitive to suspended solids, turbidity, entrained air, viscosity, color, transparency, opacity, or flow rate, and the output readings are automatically corrected for variations in process temperature. The electronic circuitry includes a signal output, adjustable in both frequency and duration, for automatic washing of the sapphire sensing window face, when/if required. The measurement is displayed in the most useful terms for that particular application. The most common read-out units are % Solids, Brix, Refractive Index and TTA.