Sensors hysteresis

Sensor hysteresis and fouling Not selective to hydrogen Limited operation range... 

Ideally, sensors should behave reversibly in response to the changes of the analyte. If they do not, we talk about sensor hysteresis. This phenomenon can be overlooked... 

Among all Fe(II) spin crossover compounds known to date, the extensively studied polymeric [Fe(4-R-l,2,4-triazole)3](anion)2 systems (R=amino, alkyl, hydroxyalkyl) appear to have the greatest potential for technological applications, for example in molecular electronics [1, 24, 25] or as temperature sensors [24, 26]. This arises because of their near-ideal spin crossover characteristics pronounced thermochromism, transition temperatures near room temperature, and large thermal hysteresis [1, 24, 27]. 

Limitations of the aluminum oxide sensor include (I) the sensor is a secondary measurement device and must periodically be culihraied to accommodate aging effects, hysteresis, and contamination and (2) sensors require separate calibration curves, which are typically nonlinear. 

Figure 10- Sheet resistance data illustrating the hysteresis in aged aluminum oxide moisture sensor. Reproduced with permission from reference 18. Copyright 1982 Institute of Electrical and Electronics Engineers.

Aluminum oxide charge-flow transistor, transfer function, 171,173,174f Aluminum oxide moisture sensor aging effects, 174f charge-flow transistor, 172f hysteresis effects, 175f... 

The nonlinearity and hysteresis have a profound influence on application of piezoelectric sensors and actuators, particularly in high precision devices. Details and additional references can be found in [4],... 

The bulk modulus cell consists of a hollow, cylindrical steel probe with a projecting stem (Figure 3.142). When exposed to a process pressure, the probe is compressed, and the probe tip is moved to the right. This stem motion is then converted into a pressure reading. The hysteresis and temperature sensitivity of this unit are similar to that of other elastic element pressure sensors. The main advantages of this sensor are its fast response and safety in effect, the unit is not subject to failure. The bulk modulus cell can detect pressures up to 15,000 bar (200,000 psig) with 1-2% full-span error. 

Only a few multinuclear cyanide complexes are known to exhibit spin crossover behavior. In all the cases described in Section IV.D, a gradual spin transition is observed, which can be explained by relatively weak intermolecular interactions in the crystal strucmres of these compounds. It is generally known that stronger interactions between individual SCO centers lead to cooperative behavior, abmpt spin transitions, and thermal hysteresis or bistability over a finite temperature range (276). The latter property renders SCO compounds attractive materials for the development of magnetic sensors and memory devices. It is expected that extended... 

FIGURE 6.7 Nonlinear zirconia gas sensor function with hysteresis. 

Dispersion of the output signal aroused by the hysteresis of the sensor function... 

The consecutive plan is widely used in many sensor experiments, especially in tests where the sequence of experiment itself is a peculiar parameter. Examples can be the sensor tests, where the sensor function is accompanied by hysteresis. 

The first restriction is an inability to use the randomization principle. It is explained by the fact that the majority of the zirconia gas sensors are based on using operational principles possessing hysteresis effects (hysteresis of the electrochemical reactions at the TPB, hysteresis of the setting-required tanperature of the sensor, etc.). 

Then, the zirconia sensor should be tested at the normal working conditions for example, examinations of its sensitivity at different temperatures, verification of the work function hysteresis, determination of the measuring concentrations range, and so on. After that, all other metrological characteristics of the sensor have to be... 

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