Absolutely extremely technical
I have a Sensirion transducer (SDP810-125PA at DigiKey $30.85) hooked up to an ESP32-S (ESP32-S3 Feather 8MB with w.FL Antenna at Adafruit $17.50). The transducer is for capturing infrasounds (< 20 Hz). Today was a milestone: the transducer detected an infrasound — its first “baby.”
I am building this experimental device inspired by the seminal work “Implementation, Characterization, and Evaluation of an Inexpensive Low-Power Low-Noise Infrasound Sensor Based on a Micromachined Differential Pressure Transducer and a Mechanical Filter” by OMAR MARCILLO AND JEFFREY B. JOHNSON of the Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, New Mexico and DARREN HART of Sandia National Laboratories, Albuquerque, New Mexico, published in American Meteorological Society in their JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY, September 2012 (link).
Here are photos of the transducer.
Basically, if one port of the sensor is exposed to open air and the other has a back pressure such as a tube to a closed container with a tiny leak in it, the transducer will be able to detect low frequencies. By placing a 15 foot tube which daylights to open air at its end on one of the ports, I created a pneumatic impedance/mechanical filter. in other words the tubing changes the pressure response seen by one side of the differential sensor. I ran two runs:
- 10 minutes with both port exposed to open air
- 10 minutes with one port connected to 15′ of 4mm (ID) tubing
And then I processed the data of both logs and it appears I have captured a 3.95 Hz frequency. See the plots at https://salemdata.net/HDC/dev/sensirion/sdp810_compare_20261006_152720.html
Though I cannot yet say what caused the 3.95 Hz signal, the experiment shows that my Sensirion-based system is responding to pressure variations in the infrasonic frequency range. Now I need to determine whether I measured the environment or my instrument.
Vogue !
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