Sensor response, speed

The process model can be obtained by different forms, and in bioprocesses mass balance equations canprovide much information. However, in order to have efficient process models and software sensors, a previous adjustment of the model is necessary using on-line data collected from a plant under different operational conditions. This databank is important to guarantee that the model remains calibrated and represents the plant adequately. Some requisites are indispensable for the experimental implementation of models in software sensors response speed to disturbances in the system and appropriate inference of primary variables of interest during key points of the process. 

For gas or ions, FET sensors response speed is not the main prerequisite because of the relatively long time constants associated with chemical measurements. However, the ON-OFF conductance ratio, as well as the transconductance IJ Vg should be maximized. As far as noise is concerned, attention shold be paid to reducing both the noise-equivalent input current zn and voltage vn generators of the sensor. In fact, the total rms input noise for unity bandwidth of such a device can be expressed in a first approximation as (Motchenbacher and Fitchen, 1973)... 

This effect is complete in the case of porphyrins 6-8,13, which behave in the same way, independent of metal present in the inner core of the macrocycle. In conclusion, the introduction of these alkyl chains from one side gives a higher porosity to the molecular film and, as a consequence, both a speed up of the response and an increase of the sensor response. On the other hand there is a significant decrease of the importance of the selective interactions in the sensing mechanism of the organic material and, as a consequence, a lowering of the selectivity of the sensor. 

The largest influence on the response speed is found to be the temperature. Wingbrant et al. has investigated the temperature-dependence of the response speed for a large number of different devices, with gate metals of 100-nm Pt + 10-nm TaSi, porous Pt, and porous Ir of different thicknesses used as both hydrogen and ammonia sensors [2] (Figure 2.18). 

Figure 2.19 illustrates the basic controls required to keep the compressor out of surge by quickly introducing an artificial load as the surge line is approached within some limit. In order to do this, the response speed of both the flow sensor and the valve must be very fast. 

Li et al. [37-39] described the use of the bacterial species Bacillus subtilis and Bacillus licheniformis entrapped between a polycarbonate membrane and a Teflon-covered DO probe. The differences between the steady-state signals before and after exposure to the test samples were used as a measure of the sample BOD levels. Riedel et al. [32-33] described the use of the yeast Trichosporon cutaneum, or both T. cutaneum and B. subtilis, sandwiched between a dialysis membrane and a polyethylene-covered DO probe. In these cases, the sensor response times were speeded up by measuring the initial rates of change of the signals. In this way, measurements could be made within 30 s rather than within 15-20 min for the steady-state approach [33]. 

The steady-state response of each sensor ( 5 min) was recorded for each substance. A training pattern was formed by converting each set of steady-state sensor responses to a bit pattern. Bit patterns generally consisted of no more than 200 bits. The low resolution of the training pattern maximized process speed for the test in an actual instrument, a small pattern size would also help to... 

Maekawa T, Anno Y, Tamaki J, Miura N, Yamazoe N, Asano Y and Hayashi K 1993 Development of semiconductor gas sensors to discern flavors of consomme soup Sensors Actuators B 13-14 713-14 Varfolomeev A E, Volkov A I, Eryshkin A V, Malyshev V V, Rasumov A S and Yakimov S S 1992 Detection of phosphine and arsine in air by sensor based on Sn02 and ZnO Sensors Actuators B 7 727-9 Hafele E, Hardtl K-H, Muller A and Schonauer U 1991 Semiconductor for a resistive gas sensor having a high response speed doped perovskite US Patent 4988 970... 

Based on the Equation (2), the speed of the sensor response (and hence time of the signal takes to fall hack to the clean air value) might be explained in terms of fundamental characteristics of the surface properties. 

A functionalized sensor with structure as shown in Fig. 7.15b had higher sensitivity and response speed. In this functionalized OFET sensor, 15 nm of 6PTTP6 and HO6OPT semiconductor blend, serving as a functionalized receptor layer, was coevaporated on top of a 35 nm 6PTTP6 film. 

OFET responses to an analyte vapor of wide interest can be enhanced by the appending of simple receptor functionality to the OSC molecules, and by the use of OSC heterostructures. Particular protocols for addressing the devices have also been developed. Thus, progress is demonstrated toward the speed, sensitivity, stability, and selectivity requirements of the national security research community. More importantly, careful consideration of many of the electronic and chemical mechanisms that could lead to sensor response allow for performance evaluation at a range of voltages, and predictions of optimal operational conditions. With the many research groups aiming to use... 

To test for sensor response time, a high shaft speed was desirable. Errors in response time resulting from liquid boil-off and measurement tolerances on actual sensors position could be kept below 2 msec by using shaft speeds between 23 and 60 in./sec. The available 6-in. stroke was sufficient to ensure that all sensors were completely submerged at the bottom end of the stroke and completely out of liquid at the top. 

The reliability of the data is important in sports performance. The system must always be able to capture the right data, in an accurate and timely manner and with the correct sensitivity. There are various factors to consider that can affect the quality of the data interference and noise caused by motion or micro-environmental conditions, hysteresis, speed of sensor response v/s sport requirement (data lag), loss of contact to the... 

Incorporation of the functionalized complex into the polymer matrix required some experimentation (7). The metal ion complexes may have limited solubility in the monomer solution. This can be addressed by adding an appropriate solvent to the mixture. The solvent has the further purpose of acting to help increase the porosity of the finished polymer. This simplifies the removal of the imprint molecule and increases the speed of the sensor response. Typically, a range of complex loading, crosslinking, and solvent addition are examined for optimal optical response. 

The converse electrostrictive effect—the stress dependence of the permittivity—is also used in stress sensors [19]. A himorph structure provides superior stress sensitivity and temperature stability. A measuring system with a himorph structure, which subtracts the static capacitances of two dielectric ceramic plates, has been proposed [ 19]. The capacitance changes of the top and bottom plates have opposite signs for uniaxial stress and the same sign for temperature deviation. The response speed is limited by the capacitance measuring frequency to about 1 kHz. Unlike piezoelectric sensors, electrostrictive sensors are effective in the low-frequency range, especially DC. 

Hughes RC, Schubert WK, Buss RJ (1995) Solid-state hydrogen sensors using paUadium-nickel alloys effect of alloy composition on sensor response. J Electrochem Soc 142 249-254 Jakubik WP, Urbanczyk MW (2005) SAW hydrogen sensor with a bilayer structure based on interaction speed. Sens Actuators B 106 602-608... 

Optimal sensor response requires a minimum and smooth downward speed of the CTD. Because of pitch and roll, this cannot be achieved on a ship. One particular approach is that records sampled at less than a pre-set minimum speed should be discarded. However, at least five records should be kept on the chosen vertical interpolation scale to avoid data with too many gaps if larger parts of the profile are at less than the minimum lowering speed for some reason. 

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