Q - Why does the CE7000A require a black trap, but other units do not?
A - Due to the precision of the CE7000 and CE7000A, it is imperative that you use the black trap for the black calibration. The CE7000 and CE7000A are very sensitive to the black calibration, and the black trap is provided to eliminate any unintentional user interference. Other units are not as sensitive, so an open port is sufficient for a black calibration.