Zero Point Calibration - KERN ORA 4 RR Operating Manual

7.1 Zero point calibration

Hold up the refractometer against a sufficiently bright light source and look
through the eyepiece [5], holding the rubber eyeshade [4] closely against your
eye/glasses.
Rotate the eyepiece [5] to adjust it for your eyesight, until you can see the
scale sharply.
Open the prism cover [1].
Thoroughly clean the prism [2] and the underside of the prism cover [1] using
a soft cloth or soft paper (with alcohol if necessary) and wipe dry. Water
should only ever be applied to the measuring prism, not to other parts of the
device.
Now apply a few drops of the calibration liquid [10] onto the prism surface [2].
The calibration liquid for the ORA 4RR is Brix 78.8% with block. Confor-
mity at 1.4875 nD
close the prism cover [1]. The amount of fluid should be sufficient to moisten
most of the prism surface. There should not be any air bubbles between the
measuring prism [2] and prism cover [1].
Wait about 30 seconds to allow the temperatures of the test fluid and prism to
equalise.
Look through the eyepiece [4] while pointing the refractometer's prism surface
[2] at a bright light source.
Through the eyepiece [4], you will see a bright and a blue field. The boundary
line between them shows the refractive index value on the scale which is also
visible through the eyepiece [4].
Use the supplied adjustment tool [11] to turn the adjustment screw [3] behind
the prism surface [2] (under the rubber cap), and adjust the scale so that the
measuring device is optimally set up. The bright/dark boundary line should be
at 0% Brix. For refractometers which are not adjusted at 0% Brix using distilled
water and have a special calibration liquid, set the bright/dark boundary line to
the calibration line in the field of view. The room temperature must be +20 °C.
For refractometers without automatic temperature compensation (ATC): Con-
vert the measured value to take account of the deviation in room and sample
temperature from +20 °C. (See the table at the end of this manual, point 13.)
Repeat step 4 (cleaning).
Important!
The ambient/room temperature and the sample temperature influence the refracto-
meter measuring result.
The scales are designed for an ambient temperature of +20 °C!
If the measurements are carried out at a temperature other than +20 °C, the results
must be correspondingly corrected.
A correction table can be found in the annex, Point 13.
ORA_4RR-BA-e-1510 8