Stationary sensor

Monitoring is basically of at least two dimensions space and time. In many cases there is a need to monitor a constant location, which means that the sensor is fixed in space and monitoring becomes only time-dependent. For this mission, a stationary remote environmental sensor is the evident option. A stationary sensor is more flexible in terms of dimensions, weight, and power supply. This flexibility also lowers the cost of the sensor. Stationary sensors are quite common, less common are stationary sensors that are controlled remotely. 

In Chapter 3 we briefly outline the methods of manufacturing of sensitive elements of semiconductor sensors in order to proceed with the studies of several physical and chemical processes in gases, liquids as well as on the surface of solids. Here we show the peculiarity of preparation of these elements depending on objective pursued and operation conditions. We outline the detection methods (kinetic and stationary), their peculiarities and advantages of their application in various physical and chemical systems. 

Of all existing methods to monitor electrical properties while using semiconductor sensors, only two [5] have become widely implemented both in experimental practice and in industrial conditions. These are kinetic method, i.e. measurement of various electrical parameters under kinetic conditions, and stationary (equilibrium) method based on the measurement of steady-state parameters (conductivity, work function. Hall s electromotive force, etc.). 

It should be noted however that the method related to the measurements of equilibrium or stationary oxygen concentrations by means of sensors is not always applicable and convenient even in this particular case. Sometimes too much time is required to conduct these measure-... 

It was first shown in study [37] that adsorption of N-atoms on films of zinc oxide reduces its conductivity to a certain stationary value which depends, as with oxygen atoms, both on the stationary concentration of particles in the volume adjacent to the sensor s film and on the temperature. 

Calculation yields that in these experiments the stationary concentration of radicals [ 4] for the maximum intensity of light of a mercury lamp SVDSh-500 was no more than 10 radicals/cm, the stationary conductivity of a ZnO film at 300 C changing by 300 to 400% compared to its initial pre-adsorption value. Thus, in accordance with the above formula (3.21), concentrations of radicals equal to 10 -10 radicals/cm may be detected by means of semiconductor sensors which is 7 magnitudes lower than existing methods would allow. 

Note in conclusion, that similar problem can he solved at temperatures of the liquid lower than room temperature. At lower temperatures one may expect longer times of establishing stationary electric conductivity of the sensor, in the first place due to lower rate constant of the reaction between adsorbed oxygen and solvent. Consequently, at lower... 

The second group of recently developed ionic liquids is often referred to as task specific ionic liquids in the literature [15]. These ionic liquids are designed and optimised for the best performance in high-value-added applications. Functionalised [16], fluorinated [17], deuterated [18] and chiral ionic liquids [19] are expected to play a future role as special solvents for sophisticated synthetic applications, analytical tools (stationary or mobile phases for chromatography, matrixes for MS etc.), sensors and special electrolytes. 

In irons, acceleration sensors are used that cause the iron to switch off when in an unwanted position or stationary. 

The rheometer most often used to measure viscosity at low shear rates is the cone and plate viscometer. A schematic of a cone and plate rheometer is found in Fig. 3.24. The device is constructed with a moving cone on the top surface and a stationary plate for the lower surface. The polymer sample is positioned between the surfaces. Two types of experiments can be performed the cone can be rotated at a constant angular velocity, or it can be rotated in a sinusoidal function. The motion of the cone creates a stress on the polymer between the cone and the plate. The stress transferred to the plate provides a torque that is measured using a sensor. The torque is used to determine the stress. The constant angle of the cone to the plate provides an experimental regime such that the shear rate is a constant at all radii in the device. That is, the shear rate is independent of the radial position on the cone, and thus the shear stress is also independent of the position on the cone. 

---