Sensors static characteristics

Poisoning and thermal aging are the main reason why the lambda characteristic and dynamics of the sensor changes with lifetime [1, 31-33]. Plugging of the porous electrode protective layer by oil, ash, or silicon oxide favors the diffusion of hydrogen to the electrode, which leads to a lean shift in the static characteristic curve [31]. 

In addition to the static characteristics, there are dynamic ones. These are related with the sensor s response to a time-related input. As sensors perform the transduction between a domain under analysis and a processable domain, the understanding of the dynamic characteristic of a sensor becomes fundamental. 

The interaction of the exhaust-gas composition with the catalytic activity of the electrode and the diffusion of the gas through the porous layers is the most important factor affecting the static and dynamic signal characteristics of the sensors. 

Figure 5 shows the dynamic response of each sensor in the array as it senses the volatiles desorbed from the fibre. The general profile reflects a combination of factors inherent within the measurement system namely desorption characteristics of the volatile species from the SPME fibre, diffusion of the volatiles through the static headspace between the fibre and the sensors and the response characteristics of the sensors to the volatiles. Different portions of the general response profiles are potentially of use in terms of resolving differences between samples and thus classifying sample types. 

There are many acoustical methods proposed for measuring flow resistivity (Delany and Bazley, 1971 Smith and Parott, 1983). A method that uses a standard impedance tube directly to measure the static flow resistivity without any additional requirements to tube modification or sensor location change is described in ISO Standard, 10534-2 (1998) and by Tao et al. (2015). In the method, the specific acoustic impedance on the front surface of the test specimen is measured first by using the traditional transfer function method with the test specimen being placed against and with a known interval to the rigid termination, and then the characteristic impedance, the propagation constant, and the static flow resistivity are calculated based on the obtained impedance transfer functions. 

A large-scale pneumatic conveying test rig was employed to transport the above four test materials. Two Afferent pipelines were connected to the test rig. The characteristics of the pipelines are listed in Table 2. The product mass flow rate, mg was determined from load cell readings and the air mass flow rate, mf was determined by an air flow sensor, Annubar. The static air pressmes were measured by the pressure transducers. 

Depending on the purpose of the application, sensors characteristics can be divided into two categories static and dynamic. It is the full understanding of the sensor characteristics that allows its performance to be assessed. 

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