From the product description, check product page for current description, price and availability:

• Easy setup and storage
• Battery operation with Low Power indicator
• Automatically turns off after 3 minutes of non-use
• Single-point calibration with distilled or deionized water

The MA884 is optical instrument that is based on the measurement of the refractive index of a solution. The measurement of refractive index is simple and quick and provides the vintner an accepted method for sugar content analysis. Samples are measured after a simple user calibration with deionized or distilled water. Within seconds the instrument measures the refractive index of the grape. This digital refractometer eliminates the uncertainty associated with mechanical refractometers and is easily portable for measurements in the field.