How is the calibrated White tile used to make a measurement. Follow
Our technical staff realized that:
a) the white tile data are located into the instrument firmware (all the instruments?) All HunterLab instruments have their calibrated white tile data stored in ROM on the Signal Processing (SP) or Data Aquisition (DA) board. When the instrument is powered on this data is moved to RAM.
b) the white tile data can be entered by a sw. The user software EasyMatch QC has no ability to load white tile data to ROM. The Diagnostic software supplied with each instrument does have the capability to load white tile data to ROM. But it is not fully clear how these values are used in the calibration and in the measurement routine.
During Standardization the following two terms are created Instrument Dark ( spectral result of measuring Light Trap or Black Glass ) and Standard White (spectral result of measuring Instrument White Tile )
When the user reads a Sample the value for the sample reading shown on the screen is calculated from the following formula;
Sample Value = ((Sample reading minus Instrument Dark) divided by (Standard White minus Instrument Dark)) times Calibrated White values
This formula is the same for all current color spectro manufacturers.
For example the MiniScan EZ and ColorFlexEZ units (stand alone mode); if the customer changes the white tile (once bought the option L02-1014-418), what will happen to the measure values stored in the instrument (sensor) database? Nothing happens to the data stored in the database. There is no reason to change that data.
Are the measures stored still valid? Of course, what would invalidate them? The white tile that HunterLab labels instrument white standard is directly assigned relative to PTFE. The difference between white tiles is much less than the difference between individual instruments.
There is any kind of correlation with the new white tile data by preventing any drift to them? I don't understand the question, do you mean "difference" instead of "drift". Drift means that the value slowly changes. Difference means that the is immediately not the same.
In case of double measure on the same sample before and after the white tile change, would you confirm the reliability of the measured value? What kind of DE we may expect? Less than inter-instrument agreement specifications.
Considering one of your instruments (sensor) connected to the software Easy Match QC how do you manage the white tile data? Since EasyMatch QC has no ability to alter the ROM in the instrument it has no ability to manage the white tile data.
To be more specific, what might happen to my data (stored in the Easy Match sw) in case of white tile replacement? Nothing happens to the stored data. Why would you think that the stored data would change?
Does the software use the white tile data stored in the instrument firmware? If yes in which way? In the equation described earlier where the ((Smp-Drk)/(Std-Drk))*Calibrated data the Calibrated data comes from the instrument firmware.
We noticed that the white tile of the instrument (sensors) are different from MiniScan EZ, UltraScan VIS, ColorFlex EZ. Is there a specific reason? MiniScan EZ, ColorFlex EZ, SpectraTrend HT, D25NC use a porcelain enameled steel white tile as their top of scale standard, this tile has curve shape that mimics TiO2 and average reflectance greater than 85%, the UltraScan Vis and UltraScan Pro use an EverWhite Japanese Opal tile as their top of scale, this tile has a curve shape that mimics PTFE and average reflectance greater than 95%.
Could You please send us a program to see how it uploads the white tile data into the firmware?
See attached instructions on how to load White tile data into an LabScan XE using LabScan XE Diagnostics software. This basic procedure is the same for all of the different diagnostics programs. Also attached is a sample White tile data file. these files have the extension .rfl and are typically named with the instrument serial number.
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