Teledyne 8800A, Operating Instructions Manual

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8800 Series Trace Moisture Analyzer Instruction Manual Appendices
47
Of course analyzing on a wet-up step will produce much faster results, because all sensors are fast
on wet up, since Al
2
O
3
(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 our 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 the Hyper-Thin-Film (HTF) Aluminum Oxide Technology notes. We can comfort-
ably make the claim that the 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).