Seven different refractometers were assessed (figure 4), including the Reichert 10440 used by the WFCS lab. Two of the models were digital, while the other five were standard hand-held analog models. These models were selected for the assessment based mainly on their price and availability. Prices ranged from $120 to $700.

Figure 4—Hand-held refractometers are held to the eye when being used.

The models evaluated were:

Some models have eyepieces that focus (ATAGO ATC–1, Bellingham & Stanley Eclipse, and Reichert Brix 35HP). All models, except the Bellingham & Stanley Eclipse, automatically compensate for temperature. The Bellingham & Stanley Eclipse includes a correction factor table to accommodate changes in temperature. The table is fairly easy to use, according to an airtanker base manager who uses the Eclipse. Additionally, all models have methods to calibrate the instrument. Digital refractometers should be calibrated daily using deionized or distilled water. Recalibration of analog refractometers should follow the manufacturer's suggestions.

Occasionally, refractometers may need to be recalibrated professionally. Tek-Net, a New Jersey company, will clean and recalibrate a refractometer for about $75 plus shipping costs. They also will let you know whether it is more cost effective to repair the refractometer than to purchase a new one.

Tek-Net
Attention: Ray Coles
1985 Swarthmore Ave.
Lakewood, NJ 08701
732–905–5530

Be sure to include your name, address, and phone number when shipping your refractometer.