Indiana University-Purdue University Indianapolis (IUPUI) / In this work we have designed and simulated a thermal bi-directional integrated circuit mass flow sensor. The approach used here was an extension to the gas flow model given by Mayer and Lechner. The design features high precision response received from analog integrated circuits. A computational fluid dynamic (CFD) model was designed for simulations with air and water Using COMSOL Multiphysics. Established mathematical models for the heat flow equations including CFD parameters were used within COMSOL simulation(COMSOL Multiphysics, Sweden). Heat pulses of 55 °C for a period of nearly 120 seconds and 50% duty cycles were applied as thermal sources to the flowstream. The boundary conditions of the heat equations at the solid (heating element) fluid interface were set up in the software for the thermal response. The hardware design included one heating element and two sensing elements to detect the bi-directional mass flow. Platinum sensors were used due to their linear characteristics within 0 ºC to 100 ºC range, and their high temperature coefficient(0.00385 Ω/Ω/ºC). Polyimide thinfilm heater was used as the heating element due to its high throughput and good thermal efficiency. Two bridge circuits were used to sense the temperature distribution in the vicinity of the sensing elements. Three high precision instrumentation low power amplifiers with offset voltage ~2.5μV (50μV max) were used for bridge signal amplification and the difference circuit. The difference circuit was used to indicate the flow direction. A LM555 timer chip was utilized to provide the heat pulse period. Simulation and experimental measurements for heat pulses with different amplitude (temperature) were in good agreement. Also, the sensitivity of the flow sensor was observed to remain unaffected with the change in the duty cycle of the heat operation mode.

Automating tasks and processes are becoming more and more common in both corporate and everyday life. The aim of this project is to assist the company Hotswap in the development of a safety system for an existing automatic flagpole. The safety system should be able to monitor wind velocity and, optionally, wind direction as well as communicate the data to the flagpole’s main control unit. The thesis describes and discusses the different possible mechanisms, solutions for measuring wind, and a possible implementation. A method for measuring wind velocity by utilizing an FS5 thermal mass flow sensor was selected and a prototype was developed for testing the performance of the implementation. The tests showed that the thermal mass flow sensor fulfilled the requirements regarding wind velocity measurement and accuracy with an average deviation of 0.19 m/s from the reference value. The solution was then discussed and compared with Hotswap’s existing prototype. The comparison showed that the prototype was a viable alternative. Finally, some suggestions for further development were presented along with the conclusion that the prototype provides a proof of concept for a fully realizable solution. / Automatisering av arbetsuppgifter och processer blir mer och mer vanligt både på företag och i vardagslivet. Detta projekt hade som mål att bistå företaget Hotswap med utvecklingen av ett säkerhetssystem för en befintlig automatisk flaggstång. Säkerhetssystemet ska kunna mäta vindstyrka och vindriktning och kommunicera den uppmätta datan till flaggstångens kontrollenhet. Rapporten beskriver och diskuterar de olika möjliga mekanismer och lösningar som finns för att mäta vindhastighet samt en möjlig implementering. En metod för mätning av vindhastighet där en hot-wire flödessensor valdes och en prototyp utvecklades sedan för att testa den implementerade metodens prestanda. Testen visade att användning av flödessensorn tillfredsställde de ställda kraven på prototypen gällande vindhastighetsmätning och mätprecision med en medelavvikelse på 0.19 m/s från referensvärdet. Lösningen diskuterades och jämfördes sedan med Hotswaps befintliga prototyp. Jämförelsen visade att prototypen var ett rimligt alternativ. Slutligen presenterades några förslag på vidareutveckling tillsammans med slutsatsen att prototypen är en konceptvalidering för en fullt realiserbar lösning.