Epson manual XDT User’s Manual Appendices

XDT User’s Manual Appendices

Of course analyzing on a wet-up step will produce much faster results, because all sensors are fast on wet up, since Al2O3 (like most materials) adsorbs faster than it desorbs. Testing with a small step e.g. in the -10°C to 0°C dewpoint range will produce even faster results, and allow manufac- turers to make far-fetched claims of response time of 5seconds for a 90% of step change. The cus- tomer has to be aware of these manipulations of data and be able to ascertain the real-world response time they can expect out of a sensor.

As can be seen from the graph the Xentaur sensor is appreciably faster than any competitors'. This is due to the Hyper Thin Film (HTF) technology, an explanation of the workings of the sensor is provided in theXentaur Hyper-Thin-Film (HTF) Aluminum Oxide Technology notes. We can comfortably make the claim that the Xentaur XTR-100 sensor is faster than any on the market today.

To compensate for their sensors' slow response some manufacturers resort to software accelera- tion of response time, even though this scheme provides a seemingly faster response to a single step change, it creates great errors in real systems where multiple changes occur consecutively in differing directions. The sensors' real response lag to consecutive step changes in differing direc- tions is erroneously interpreted as belonging to a single step change, and thus large errors of mea- surement are introduced for long periods of time. An analogy of this situation can be imagined with a defender in a football (soccer) game. A slow player cannot defend by just anticipating the next move of the forward wing; he will simply be faked out by a series of back and forth maneu- vers (consecutive step changes in differing directions). While a fast defender cannot be faked out, he simply follows the forward wing as fast as he moves (Hyper Thin Film).

47