Real Time Data from US East Coast
Nelson-Nordgren, Astatic Spring, Broadband Force Balance, Vertical (FBV) Seismometers

  • Local Weather Conditions (Weewx on Pi-Zero)
  • Yuma Waveforms
  • Lenape Waveforms
  • Seneca Waveforms
  • OSOP RPi Shake 1D-V5

    Metrozet PBB200S High Gain Output, 24 bit Digitizer, Filtered for Distant Events

    Sensitivity: 1500V/m/sec over a bandwidth of 120 seconds to 50 Hz Configuration: Non-Galperin design with three force feedback sensors in Z, N-S, and E-W directions

    WinSDR updated every 5 minutes. YDivisor = 6, Filtered 0.002 Hz - 0.07 Hz, 100 samples/sec

    Metrozet PBB200 Low Gain Output, filtered for Local Events

    Metrozet PBB200S Period extended to 240 seconds


    1. Background
    2. Yuma Specifications
    3. Data Acquisition
    4. Raspberry Pi 3B Data Acquisition
    5. 3-28-2018 Installing WinSDR on Raspberry PI
    6. Hardware Photographs
    7. Solid Earth Tides
    8. Noise Power Spectral Density
    9. Whole Earth Oscillations
    10. Coherence Analysis with Pressure
    11. Real Time Atmospheric Pressure
    12. Lenape and Seneca Experiments
    13. Seneca II
    14. References
    15. Unit Conversions


    The Yuma Force Balance Broadband Verticle (FBV) Seismometer is the second in a series of three designs: the Inyo, the Yuma, and the still experimental Napa Seismometer. Each design is less than half the size of the preceding model, but each retains the same basic design principles of an astatic leaf-spring suspension and broadband force balance electronics.

    Dave Nelson of Palos Verdes, California, created the instrument's electronic and mechanical designs and has continued to perfect them over the years in a close collaboration with Brett Nordgren of Berkeley Heights, New Jersey. Brett, described as a Feedback Control System "guru", has produced dozens of white papers and spreadsheets which provide a detailed theoretical underpinning for these instruments. Brett has also provided supberb CAD drawings which allow anyone to reproduce these seismometers. Dave and Brett make available critical parts such as the 17-7 Precipitation Hardening Stainless Alloy leaf-springs, circuit boards, Kapton flexures, and high leakage resistence, (~20,000 MegOhm) capacitors. Brett and Dave are active on an email listserver along with a community of builders and people interested in the fascinating subject of Seismology. All are more than happy to assist the new builder. For more information email Brett at: .

    Yuma Specifications

    These Yuma Seismometers are located approximately 3 miles South of Princeton, NJ in central New Jersey, Mercer County. It is located between the physiographic provinces of the Coastal Plain and the Piedmont. They are underlain by the Pennsauken and Stockton Formations. These regions consist of sedimentary rock such as siltstone, shale, sandstone and conglomerate6. The instruments are located in the basement of a two story dwelling on a concrete surface in a quiet residential neighborhood. The Amtrack and NJ Transit NorthEast Corridor high speed line is located about two miles North-West of the instrument location.

    1. Response flat to velocity in the 0.02 Hz to 30 Hz band
    2. Instrument outputs: high gain, low gain, internal temperature, and centering force
    3. Coil Forcing Constant Gn: 10.4 Newtons/Ampere
    4. Coil Resistance: 41 Ohms
    5. Generator Constant (Ag): 285 Volts/Meter/sec
    6. Ag High gain output, (Ag HI): 28,300 V/m/s
    7. Ag Low gain output, (Ag LOW): 566 V/m/s
    8. Boom Period: 3 seconds
    9. Boom Moment, M0: 89.0 grams
    10. Integrater voltage vs. temperature: -309 mV/°C
    11. Spring constant error: -245.4 ppm/°C, Ri = 15K ohms
    12. Output velocity error with temberature: (42.3 um/s)/°C/hr.
    13. Quantization: 305.2 uV/Count
    14. Clipping level (HI) output: 353 um/s
    15. Clipping level (LOW) output: 1.8 cm/s

    Data Acquisition

    Larry Cochrane has designed an extremely cost effective 16 bit scanning A/D board which is well suited for Seismology. He is the auther of WinSDR and WinQuake, display and analysis earthquake software which use his hardware. His software runs on x86 hardware running Windows and under Wine on Linux. See Larry's website for further information on his hardware and software.

    Specifications from Larry Cochrane's site:

    PSN-ADC-USB Version III Board, Firmware V1.6

    1. Analog Inputs:
      • Channels: 8 Single-Ended Inputs (Note 1)
      • Resolution: 16-Bit Successive Approximation
      • Accuracy: 16 Bits
      • Dynamic Range: 96 db
      • Input Range: ± 5 or ± 10 Volts, Jumper Selectable
      • A/D Converter Chip: Linear Technology LTC1605CN
      • Input Impedance: 4.7k or 100k (Note 2)
    2. Sample Rates:
      • 500, 250, 200, 100, 50, 20 and 10 Samples Per Second (Note 1)
    3. GPS Support:
      • Supports these GPS Receivers: Garmin GPS 16 / 18 Sensor or the Motorola ONCORE series of GPS receivers
      • ± 3 Millisecond Time Accuracy when Receiver is Locked to GPS Time
    4. Board Size:
      • 6.500 x 5.750 Inches or 16.5 x 14.6 Centimeters.
    5. Power Supply Requirements:
      • 15 to 28 VDC at ~100 MA
    6. Notes:
      • At 500 SPS the board can record up to 4 channels 
      • Other input impedance possible by changing one resistor pack

    Hardware Photographs

    This photo shows how the Yuma is made up from simple parts which could conceivably be made with a hacksaw, electric drill and file. The robust design allows for adjustments so extreme accuracy is not required. These particular parts were fabricated with a small Grizzly lathe and milling machine. At this stage there are dozens of holes and thread taps remaining to be done. Note: these parts represent two Yuma Seismometers.

    Fabrication complete with one Yuma test fitted

    Completed Yumas with main electronics, center of gravity weight, balance adjustment weights, sensor plate, and leaf-springs.

    Yuma is installed in gas tight (IP67) Hammond enclosure, IP67 DB-15 connector with warpless design fittings. Note, the bottom cover of the case was drilled and tapped to allow for top mounted retaining knobs.


    1. West Coast Online Experimental Nappa Seismometer
    2. West Coast Online Yuma Seismometer
    3. Brett's FVB Archive Files
    4. USGS Recent Worldwide Earthquakes, 1 Day M2.5+
    5. l'Universite de Bourgogne Earth Modes
    6. State of New Jersey Geological Survey

    Unit Conversions