How to Standardize in TTRAN Total Transmission mode in EasyMatch QC Follow

FAQ: "We have the ColorQuest XE in our lab and are attempting to do a standardization in TTRAN Mode for the first time. I see in the directions that the black tab is placed inside, but it doesn't clearly specify if the light trap is placed outside like for the reflectance standardization, or if that area is left exposed to ambient light. Could you please explain how it should be set up?"

Technically you always standardize at the same place that the sample is being measured. So if it is in TTRAN, you place the light blocker in the transmittance compartment against the sphere. The light blocker is a black anodized plate with a little handle on it. You can place the Light Blocker at the TTRAN port. This bottom-of-scale standardization step blocks light getting to the lens and on to the detector, giving the instrument a reference for what is 0% transmittance. For this Light Blocker step, it does not matter what is at the reflectance port because you are blocking light from the position of the Light Blocker forward to the lens and detector. 

Setting the top-of-scale to 100% is similar. In this case you put a white tile at the reflectance port that fills in the sphere. It stays there for all subsequent measurements because effectively, it is part of the sphere wall. The instrument is standardizing on Air for transparent solid samples like plastic plaques, or if measuring transparent liquids, a cell of some path length filled with distilled water.

After successfully standardizing in TTRAN transmittance, read back the top-of-scale (Air or cell + distilled water) as a PQ Performance Qualification step. If you set it to 100% transmittance, it should always read L* = 100, a* = 0, b* = 0 if you are set up correctly. If so, you are performance qualified to continue with sample measurements.

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