Moisture sensors

Capacitive Sensors. This device usually consists of a capacitor which is formed either from two concentric cylinders or from a pair of parallel plates. The solid sample to be analyzed for moisture content is passed between these plates. Since w has a large dielectric constant, the w content of the sample causes a significant change in the dielectric constant of the solid, which is measured using bridge or frequency techniques. 

P. J. Prado 2001, (NMR hand-held moisture sensor), Magn. Reson. Imag. 19, 505-508. 

Electrical resistance blocks Measures resistance resulting from a gradient between the sensor and the soil higher resistance indicates lower soil moisture Consists of electrodes embedded in a gypsum, nylon, or fiberglass porous material... 

Russell A.P., Fletcher K.S., Optical sensor for the determination of moisture, Anal. Chim. Acta 1985 170 209. 

Fig. 1.98. Schema of the fiber-optic sensor to measure the residual moisture content (RM) through the bottom of the container with the product.

A new desiccant formulation was prepared from a mixture of submicron-sized silica gel and molecular sieves to achieve the best combination of large water capacity, rapid moisture adsorption and easy regenerability. The formulation also tolerates the presence of VOCs and smokes. Commercial NaX and silica gel were crushed and mixed in the proportion of 1 2 and wash coated on a monolith for testing. The same test cell shown in Fig. 12.7-2 was used. The airflow to the saturator was adjusted to obtain the desired humidity in the feed air. Humidity sensors located at the flow cell inlet and outlet, were used to... 

Belt with nucleonic sensor <25 (or <0.3 m3/s) 0.5 to 1 Preferred when material is difficult to handle, e.g. corrosive, hot, dusty, or abrasive. Accuracy greatly improved when particle size, bulk density, and moisture content are constant, when belt load is 70-100 per cent of maximum. 

Material balance analysis proves to be a critical diagnostic tool for the development of portable DMFC systems. In this analysis methanol balance on the anode side along with the methanol crossover rate typically measured by an infrared CO2 sensor is conducted. In addition, water balance on both anode and cathode sides is performed in which the cathode water amount is carefully collected by a moisture trap and measured. From such analyses Muller et al. " revealed that the water balance on the DMFC anode is highly negative, thus calling for membrane development with low water crossover in addition to low methanol crossover. 

Figure 9.11 Predicted and measured plot for granule moisture contents, calibrated on data from 5 months of production. Sensor B was used in this model (eight PLS components). Cray curve measured, black curve predicted.

J. Rantanen, S. Lehtola, P. Ramet, J. Mannermaa, J. Yliruusi, On-line monitoring of moisture content in an instrumented flnidized bed grannlator with a multi-channel NIR moistnre sensor. Powder TechnoL, 99(2), 163-170... 

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