Stat Fax 303 Plus - Calibration and Linearity Verification

36 Stat Fax 303 Plus Operator’s Manual Rev. J Awareness Technology, Inc.
2.4.5 Calibration and Linearity
Every instrument is calibrated during manufacture, using standards whose absorbance readings
are traceable to the NIST. Each instrument is also tested to verify its linearity to 2A. No
calibration adjustment is accessible to the operator, since the pre-set calibration is very stable.
Absolute calibration can not be readily verified without using a specifically designed product
called DRI-DYE
®
Check Strips, available from your instrument supplier. This is because in
vertical photometry, the fill volume and degree of meniscus determine the pathlength, and
absorbance is proportional to pathlength.
For lab test results that are based upon standards rather than upon absolute absorbances, the
linearity of the instrument is the more critical indicator of instrument performance. A gradual
reduction in linearity is indicative of filter degradation. If this occurs, filter replacement will be
required for continued reliable operation. A monthly verification of instrument calibration and
linearity is recommended. Such monitoring can be done using DRI-DYE Check Strips
®
. There is
more information about DRI-DYE Check Strips
®
in the Appendix.