A Resonant Photoacoustic CO2 Sensor Based on MID-IR LED and MEMS Microphone Technology Operating at 4.3μm

This paper presents work on the development of a MID-IR LED-based photoacoustic (PA) Carbon dioxide (  sensor. The transducer used is a MEMS microphone and the sensor was operated in the resonant mode, which makes it the first time that this light source and transducer combination are used in this mode for PA gas sensing, as far as the authors know. Optimisation of the sensor’s operation in the resonant mode was done using COMSOL Multiphysics to simulate the fundamental resonance frequency of the PA cell and the optimum position for the microphone. The COMSOL Multiphysics and analytical results computed were validated experimentally. Reduction of the inlet and outlet pipes diameter immensely minimized gas flow noise introduced into the PA cell. Cheaper, miniaturised and stand-alone PA sensors can be produced from Mid-IR LEDs and MEMS microphones because they are small in size, inexpensive and consume less power. The importance of this work largely lies in the fact that the huge market demand for this type of sensors could be met by higher volume production at low cost using this technology. Ultimately the work will be an effective contribution to the monitoring and control of carbon emission. Keywords: Photoacoustic, Mid-IR LED, MEMS microphone, resonance, COMSO

Firmware-based Capacitor and Equivalent Series Resistance (ESR) Meter

This paper presents the development of a capacitor ESR meter, which covers capacitance and ESR measurements as well as the interrelationship of the constituent parts/circuits. The idea is to keep the hardware design simple, transferring the complexity to firmware which controls the hardware. In particular, it uses automatic functions controlled by relays thus there is no need for switches and its automatic calibration ensures there is no need for menus. This work covers voltmeter function, C/R time constant function and ESR function using Arduino Uno boards. Each firmware code was developed one after the other, starting with the voltmeter function then C/R time constant function and finally ESR function. Results were checked by serial data transfer from Arduino Uno board to the laptop that is running the Arduino compiler with terminal. One Arduino Nano interface was constructed to interface the project shield. The firmware was developed to provide the voltmeter function, C/R time constant function and ESR function. An organic light-emitting diode (OLED) display was used to show measurement results. Logic control was added to provide the required functions to work as intended, as well as an automatic short circuit detection at DUT terminals firmware which includes a calibration cycle. Conventional ESR meters are usually have complex hardware, in contrast the design presented in this work shifts the focus to the firmware so that hardware is uncomplicated. This reduces the cost that typically comes with more hardware components. Keywords: Capacitor, ESR Meter, C-R Time Constant, Arduino, OLED Display, Calibration DOI: 10.7176/CEIS/13-1-02 Publication date: January 31st 202