Sensing mode

Notice, that with these extremely good resolutions in case of surface sensing contamination of the sensitive layer with solid particles has to be avoided completely, e.g. by an appropriate filtering of the sample solutions. Notice also that the temperature coefficient of the refractive index of water is about 10-4 per °C. So if applying the surface sensing mode using watery solutions indeed a perfect balance of both branches and low temperature gradients have to be aimed at. 

The third block in Fig. 2.1 shows the various possible sensing modes. The basic operation mode of a micromachined metal-oxide sensor is the measurement of the resistance or impedance [69] of the sensitive layer at constant temperature. A well-known problem of metal-oxide-based sensors is their lack of selectivity. Additional information on the interaction of analyte and sensitive layer may lead to better gas discrimination. Micromachined sensors exhibit a low thermal time constant, which can be used to advantage by applying temperature-modulation techniques. The gas/oxide interaction characteristics and dynamics are observable in the measured sensor resistance. Various temperature modulation methods have been explored. The first method relies on a train of rectangular temperature pulses at variable temperature step heights [70-72]. This method was further developed to find optimized modulation curves [73]. Sinusoidal temperature modulation also has been applied, and the data were evaluated by Fourier transformation [75]. Another idea included the simultaneous measurement of the resistive and calorimetric microhotplate response by additionally monitoring the change in the heater resistance upon gas exposure [74-76]. 

Calorimetric Sensing Mode for Operation at Constant Temperature... 

A problem of the calorimetric sensing mode is its cross-sensitivity to changes in ambient temperature. The realization of an additional temperature sensor on the bulk chip solves this problem. The signal-to-noise ratio of the calorimetric mode... 

Hydrogen detection. Detection of hydrogen (H2) is based on its high solubility in palladium. H2-induced lattice expansion of Pd causes the latter to swell, changes its conductivity and refractive index. The swelling effect can be sensed with FBGs in strain sensing mode. 

Another possibility is switching between the sensing and actuating functions of the IPMC. The same pair of electrodes can be used along with a switching control to switch from an actuation mode to a sensing mode. 

Response times for the lactate dehydrogenase biosensor in either the lactate or pyruvate sensing mode range from 6 to 12 minutes. Faster response is obtained with higher concentrations. In addition, the lifetime of this sensor is from 3 to 7 days depending on the extent of enzyme loading and the storage conditions. 

Table 36.2. Various sensing modes of proton conductor H2 sensor...

Sensing mode Sensor signal characteristics Remarks Ref. 

ESTIMATING S0 STRESS BY CHLOROPHYLL FLUORESCENCE MEASUREMENTS WITH ACTIVE SYSTEM USED IN THE REMOTE SENSING MODE... 

We will first outline the scope of this chapter. The emphasis is on principles and problems associated with the use of these materials rather than on providing an exhaustive review of the literature. The examples quoted are intended only as illustrations of specific aspects. In the first section we will address the general aspects of preparation of selective layers based on EPs and their interactions with chemical species present in the sample, i.e. the issue of selectivity. The specialized use of polymers as barriers is also included here. The use of electroactive polymer layers in three principal transduction sensing modes is then discussed. Each of these sections contains examples of typical applications of electroactive polymers for chemical sensing. The overview, comparisons and future directions are discussed in section 10.6. 

Yang, W. Lai, R. Y. Integration of two different sensing modes in an electrochemical DNA sensor for approximation of target mismatch location. Electrochem. Commun. 2011,13, 989-992. 

Sensor configuration Sensing mode PO2 range 90 % response time Refertmce... 

Sensor configuration Sensing mode Pq2- range T ( C) Response time (90%)... 

Maximum actuation strain (%) 380 120 Free strain. Strain in generator and sensing modes can be greater than that in actuation. 

All tests were remotely controlled from a control room located approximately 800 m away from the test cell. All pressure, temperature, and flow data was recorded using a computer DAQ. A picture of the screen used to determine the LL in the tank is shown in Figure 9.7. Diodes were used in dual sense mode as temperature or liquid level sensors, as controlled on the right hand side of Figure 9.7. All data was scanned and recorded at 2 Hz. A camera was used to detect LAD breakdown, and the video feed was sent to the control room monitor to view the LAD output in real time. 

In addition to the modes described in the above sections, several other sensing modes have been employed with CPs. All of these however have either been unsuccessful. 

Outline the principles of working of the six primary and two derivative modes of sensing with CPs identified in Sec. 17.1 and at least two other sensing modes identified in Sec. 17.9. 

---