K-Patents PR-01-S - Manual (Page 39)

INSTRUCTION MANUAL FOR K-PATENTS PR-01-S (-AX/FM/CS) DOCUMENT/REVISION No. INM 1/14
Effective: May 15, 2009
37
5.4. BENCH CALIBRATION
The calibration can be checked off-line using Standard RI liquids. The exact procedure is described in a
separate K-Patents brochure No. IV95 “Instrument Verification For ISO 9000 Quality System”. The
"Standard RI(25 °C)" display should then show the corresponding value.
The check should be done at room temperature, but the temperature does not have to be exactly 25 °C as
the displayed value is temperature compensated. If the sensor is hot, let it cool down to ambient
temperature.
Standard RI (25 °C) Display: For Standard RI bias = 0, the indication is 0.0000. For off-set adjustment
(like in Section 5.1), the RI bias change has to be multiplied by 100. E.g. if indication is 0.0004 low, add
0.04 to the bias for RI bias (25 °C).
Standard RI liquids are also available directly from: Cargille Laboratories, 55 Commerce Road, Cedar
Grove, New Jersey 07009, USA. WWW: http://www.cargille.com/, e-mail: [email protected], phone:
(973) 239 6633, fax: (973) 239 6096.
A 12 bottles set of RI liquids are also available at K-Patents with part number PR-2000.
Figure 5.40 Sample holder.
Use a sample holder kept in place by a rubber link, Figure 5.40. Then just a few drops of sample are
enough. Avoid strong direct light on prism. Sample leakage from holder may give measurement error.
Always use repeated measurements for each sample. Sample holders are available at K-Patents (Part
number PR-5002).
Dispose of used RI-liquids. Do not put liquids back into the bottle after use!
Off-line calibration using process liquid seldom gives reliable results, problems are caused by
– low flow which makes sample to form an unrepresentative film on the prism
– sample evaporation at high temperature or undissolved solids at low temperature giving deviations
from laboratory determinations
– an ageing sample which is not representative
Calibration using the process liquid should be made in-line, see Field calibration (Section 5.3).