Measuring Air Speed With a Low-Power MEMS Ultrasonic Anemometer via Adaptive Phase Tracking

Abstract

Indoor air movement affects many functions of buildings, including ventilation and air quality, comfort and health of occupants, fire safety, and building energy use. Accurately measuring air movement has been difficult and expensive over extended periods of time, especially for velocities below 1 m/s. A new type of high frequency ultrasonic transceiver provides high sensitivity measurements and low cost through microelectromechanical systems (MEMS) manufacturing. However, at high frequencies, conventional ultrasonic signal processing algorithms function only over small ranges of ambient temperature and velocity. In this paper, we describe three algorithms that use the complex phase angle of an ultrasonic pulse to measure velocity and temperature over extended ranges of temperature and velocity. They employ heuristics to track the vibration cycle of the measured phase angle. These methods are applied in a pulse-based anemometer whose 176kHz MEMS transceivers both transmit and receive. In wind tunnel tests between 0-4 m/s, the tracking algorithm with a low-pass filter measured air speed with high sensitivity and accuracy (0.026 m/s mean absolute error). The ability to monitor to this accuracy with such low power draw and low cost is currently unprecedented in the industry.

Towards utilizing internet of things (IoT) devices for understanding individual occupants' energy usage of personal and shared appliances in office buildings

“…While the energy efficiency of building physical systems (e.g., HVAC&R, lighting, and water heating) has substantially been improved through technological advancements, energy savings through more energy-conscious behaviors are often ignored [3,4] . Adopting energy-saving behaviors among occupants is widely accepted as one of the most economical and feasible approaches to reduce the energy consumption of office buildings [5][6][7][8][9][10][11][12] . If occupants are educated to adopt appropriate energy-saving behaviors and practice such behaviors, it provides an opportunity for energy savings within all built environments [13] .…”

Three‐dimensional analysis of the effect of human movement on indoor airflow patterns

“…The ultrasound sensing system, utilized to log 4 data points of 3‐dimensional air velocity components per second, was developed indigenously at the Center for the Built Environment in University of California, Berkeley. At the heart of this lightweight and portable sensor, there is a CH‐101 ultrasonic transceivers, utilizing new microelectromechanical systems technology for ultrasonic range finding 44 . A tetrahedral arrangement of four such transceivers, minimum required number to capture 3‐D flow, was used that provided enhanced measurement redundancy.…”

Artificial Intelligence for Efficient Thermal Comfort Systems: Requirements, Current Applications and Future Directions

“…By outfitting mechanized windows and window shades with anemometers and light meters, respectively, the system would be able to detect changes in the airflow and intensity of sunlight and automatically adjust the operation of windows and shades to preserve a comfortable thermal environment. Duct anemometers can also be installed in the ducts of the HVAC system that can notify the user of the airflow movement within certain ducts (Ghahramani et al, 2019b). This will help users deduce whether retrofits are needed and more accurately dictate the setpoints for the HVAC system.…”