Description

Refractometer 1.435 to 1.520 oil tester

Calibration should be conducted at the start of each day or when any shifts in ambient temperature occur. If recalibration is impractical, refer to the directions for temperature correction on the following page. For standard calibration procedures, please follow the directions below.
Open the daylight plate and apply one or two drops of a liquid standard on to the surface of the prism [a 1.504 nD @ 20°C oil standard is used for this example. A prepared solution of a known concentration (minimum 1.435 nD) may also be used for calibration purposes]. Hold the prism at an angle close to parallel with the floor so the liquid standard will not run off of the prism.
Gently close the daylight plate over the prism. The liquid standard should spread as a thin, even layer in between the daylight plate and the prism. By looking through the daylight plate, ensure that the liquid standard covers the ENTIRE surface of the prism. If there are bubbles and gaps or if the liquid standard is only on one portion of the prism, the liquid standard must be reapplied (Figure 1). Inaccurate calibrations will result if the prism is not covered correctly.
Looking through the eyepiece, hold the refractometer and direct the daylight plate upwards towards light. If the scale is not in focus, adjust it by gently turning the eyepiece (rubber hood) either clockwise or counterclockwise. Be careful not to overturn the focusing mechanism.
When the refractometer scale is viewed through the eyepiece, the upper field of view will be seen as blue and the lower field will be seen as white (Figure 2). Confirm that the boundary line crosses the scale at “1.504” (or the value of the liquid standard being used) (Figure 3).
If the boundary line falls above or below “1.504”, gently loosen the set screw on the calibration ring. While looking through the eyepiece, gently turn the calibration ring clockwise or counterclockwise until the boundary line is at “1.504.” Once this is achieved gently tighten down the set screw. (NOTE: Do not over-tighten. If the set screw is over-tightened, the boundary line may shift slightly).
When calibration is complete, gently wipe the prism using tissue paper