1. Look for a digital refractometer with a high accuracy rating. The accuracy rating should be at least 0.001 Brix or 0.1% salinity.

2. Check the range of the refractometer. The range should be wide enough to cover the range of measurements you need to make.

3. Look for a digital refractometer with a large, easy-to-read display.

4. Make sure the refractometer has a durable construction and is made from quality materials.

5. Check the warranty and customer service offered by the manufacturer.

6. Consider the cost of the refractometer. Quality digital refractometers can be expensive, but they are worth the investment if you need accurate measurements.