Implementation, characterization, and evaluation of an inexpensive low-power low-noise infrasound sensor based on a micromachined differential pressure transducer and a mechanical filter

The implementation, characterization, and evaluation of a low-cost infrasound sensor developed at the Infrasound Laboratory at the New Mexico Institute of Mining and Technology (Infra-NMT) are described. This sensor is based on a commercial micromachined piezoresistive differential pressure transducer that uses a mechanical high-pass filter to reject low-frequency outband energy. The sensor features a low-noise, 2.02-mPa rms (0.5-2 Hz), 5.47-mPa rms (0.1-20 Hz), or 5.62-mPa rms (0.05-20 Hz), flat response between 0.01 and at least 40 Hz; inband sensitivity of 45.13 ± 0.23 μV Pa ^-1; and a nominal linear range from 2124.5 to 1124.5 Pa. Intended for outdoor applications, the influence of thermal changes in the sensor's response has been minimized by using a thermal compensated pressure transducer powered by an ultralow drift (<5 ppm °C ^-1) and noise (<4μV from peak to peak) voltage reference. The sensor consumes a minimum of 24 mW and operates with voltages above 8 V while drawing 3 mA of current. The Infra-NMT specifications described above were independently verified using the infrasound test chamber at the Sandia National Laboratories' (SNL's) Facility for Acceptance, Calibration, and Testing (FACT), and the following procedures are for comparison calibration against traceable reference stands in voltage and pressure. Because of the intended broad frequency response of this sensor, the testing chamber was configured in a doublereference sensor scheme. A well-characterized microbarometer (with a flat-amplitude response between 0.01 and 8 Hz) and a microphone (with a flat-amplitude response above 8 Hz) were used simultaneously in this double-reference test configuration.