Servomex NanoTrace DF-760E, Instruction Manual

Page: 146 / 182

142 DF-760E Theory of Operation
The Stablex electrode pair effectively isolates the sensor cathode from the interference
caused by oxygen that is dissolved in the electrolyte. The Stablex cathode, located directly
in front of the sensor cathode, removes dissolved oxygen. Stablex provides an active
dissolved oxygen barrier and removes the need to sparge the electrolyte. (Sparging
involves bubbling pure nitrogen through the electrolyte and it causes significant levels of
electrochemical interference to the oxygen measurement process)
10.2
The Moisture Measurement
Figure 144: Schematic of Moisture Cell
10.2.1 Moisture and the IR Spectrum
The NanoTrace Moisture Analyzer uses infrared (IR) absorption as its detection method.
IR absorption is but a subset of the overall field of “spectroscopy,” which measures the
interaction of light and matter.
The basis of absorption spectroscopy is when an electromagnetic wave (i.e., the scientific
description of “light”) with a particular wavelength impinges on a substance that absorbs a
fraction of the total electromagnetic radiation. The wavelength of radiation is well known,
for instance, in differentiating colors in the visible light spectrum.
In the infrared spectral region, the wavelength of light overlaps with discrete absorptions
created by molecular vibrations. IR absorption is often used in diagnosing molecular
composition based on “fingerprints” of these absorptions over a wide wavelength range.
Conversely, if the strength of a single vibrational absorbance is known, a single
wavelength is often used to determine the amount of a particular substance. This is how
we measure moisture.