Real Time Data from a US East Coast Infrasonic Pressure Detector used to Determine Effects on Two Yuma Seismometers

Infrasonics is the study of sounds beneath 20 Hz down to 0.001 Hz. It is used for monitoring earthquakes, waterfalls, volcanoes, thunder, tornadoes, charting rock and petroleum formations below the earth, geomagnetic activity, ocean waves, and also for monitoring underground and above ground nuclear explosions. The Comprehensive Nuclear Test-Ban Treaty signed in 1963 was due, in part, to the successful deployment of a global infrasonic monitoring network. Infrasound has the ability to cover long distances with little dissipation.

The data collected here will be used to determine the possible effects of atmospheric pressure variations on Two Yuma Seismometers.

This microbarograph used to detect infrasound uses an Ashcroft Low Differential Pressure Transducer XLdP. It uses a single crystal Silicon and Aluminum diaphram capacitor for the sensor.


  1. Measurement range: 0.25 inches water column (WC)
  2. Accuracy: 0.5%
  3. Interface: 4-20 ma current loop
  4. Output voltage span: 1-5V with 250 Ohm resistor and 24 V Supply
  5. Reference volume: 0.5 Liter glass vacuum bottle
  6. Control leak: 10" length of stainless capillary tube (0.006 in ID)
  7. High pass corner frequency: 0.32 mHz at 71F
  8. Quantization for 16 bit digitizer: 0.019 micro bar per count (ubar/count), 61 uV/count

Unit Conversions: 1 Atmosphere = 29.9 inches Hg = 406.4934 inches H2O = 14.7 psi = 1,012,530.2 ubar

This 24 hour output from WinSDR is updated every 5 minutes, with a gain divisor of 50, no filtering, and sampled at 100 SPS. The vertical scale is 34.7 ubar per line. Note: a green line in the data indicates the instrument is offline.

Event Frequency Ranges:

Simple micro barometer using glass thermos and Ashcroft pressure transducer. A port for a syringe pump allows for measurement of the time constant.