The metrological aspects related to the sensitivity and signal-to-noise ratio of the auto-normalized front pyroelectric technique for the measurement of thermal effusivity in liquids are investigated. The effect of the thermally thick approximation in the theoretical expressions for the photopyroelectric signal and its effect on the sensitivity of the technique are discussed. It is shown that the sensitivity of the technique decreases with frequency. In contrast, the signal-to-noise ratio increases for higher frequencies.

A microscale jet ejector driven by ethanol vapor is designed and tested to induce a suction draft using a supersonic converging-diverging micronozzle. A three-dimensional axisymmetric nozzle is fabricated using electro-discharge machining to produce a throat diameter of 187 μm with an expansion ratio of 3:1. The motive nozzle achieves a design mass flow efficiency of 93% compared to isentropic calculations. Two different ejector area ratios are compared using ethanol vapor and nitrogen gas separately to motivate and entrain ambient air. The experimental data indicate that the ejector can produce a sufficient suction draft to satisfy both microengine mass flow and power off-take requirements to enable its substitution for high-speed microscale pumping turbomachinery.

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Productive activities require measuring systems as a key tool for manufacturing quality goods. Metal mechanical industries develop their processes based on the control of a high precision fit between two pieces of a pressureassembled product. Therefore, engineering materials are constantly subjected to resistance tests. Balance test equipment and mechanical vibrations work under the principle of force measurements. The most precise stress measurement methods are done with electromechanical devices known as load cells. They basically consist of a tiny electric resistor that is adhered to a mechanical element that may be under stress. Cyclic stresses also directly affect the performance of the measuring element including the resistance itself, which changes as the cyclic fatigue progresses (the measuring element is a very thin coil with limited strength). In this research, we developed an optomechatronic load cell 1 whose operating principle is based on measuring the stress load applied to a mechanical element. The deformation causes a reduction in the distance between the emitter and the receptor producing an electrical signal. It must be established that the distribution of the light intensity varies between the emitter and the receptor due to the generated displacement. An infrared emitter was adapted to the load cell whose signal was received by the receptor at the other end. The second stage included a demonstration that the optoelectronic system is capable of measuring external stresses on a mechanical element by using an indirect method of measuring stresses. Here we present the results from those experiments, which include some adaptations on the mechanical element. We implemented a prototype sensitive to the deformation produced by the mechanical element (load cell). As a result of the two stages, we plan to test the system in academic and industrial applications. The third step in the research is to validate the optomechatronic load cell under the E74-065 ASTM Standard 2 showing the results based on the resolution, sensitivity, and repeatability required by the standard.