Biomedical Engineering Reference
In-Depth Information
3. An indicator or chemical reagent placed inside, or on, a polymeric support near
the tip of the optical fiber is used as a mediator to produce an observable optical
signal. Typically, conventional techniques, such as absorption spectroscopy and
fluorimetry, are employed to measure changes in the optical signal.
2.6 Analytical Measurement Sensor
Many chemical composition measurements may be made indirectly by means of
electricity, if those measurements are related to the concentration of ions (elec-
trically charged molecules). Such measurements include:
• pH of an aqueous solution
• Oxygen concentration in air
• Ammonia concentration in air
• Lead concentration in water
Humidity Measurement
Gas or air humidity measurements are becoming more and more important.
Constant improvements to the technical processes, higher demands on quality and
energy saving require an accurate, stable, and affordable measuring procedure to
measure air humidity.
Dew point Measurement
Humidity measurement finds wide applications in different process industries.
Moisture in the atmosphere must be controlled below a certain level in many
manufacturing processes, e.g., semiconductor devices, optical fibers, etc. Humidity
inside an incubator must be controlled at a very precision level. Textiles, papers
and cereals must be dried to a standard storage condition in order to prevent the
quality deterioration. Figure 2.15 shows the dew point meter illustration.
The humidity can be expressed in different ways:
1. absolute humidity,
2. relative humidity, and
3. dew point [ 12 ].
Various types of analytical sensors comparison is shown in Table 2.10 .
2.7 pH Sensor
pH is a parameter to indicate the level of acidity or alkalinity in a chemical
solution. It defines
the
concentration
of
hydrogen
atoms
in
the
solution
in
grams/liter and is expressed as:
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