Sensor - GeoPhone

date
Jun 10, 2024
type
Post
AI summary
slug
esp32-geophone
status
Published
tags
sensors
summary
 
Example of usage with a Raspberry Pi: link
 
The A3HV 315/1 triaxial geophone is manufactured by Sercel, a well-known company specializing in seismic acquisition equipment and geophysical instruments. Sercel provides a range of products for seismic data acquisition, including land, marine, and downhole applications.

Commercially Available Products

https://rstinstruments.com/product/rock/

Typical Frequency Range for Structural Geophones

In structural engineering, geophones are used to monitor vibrations and seismic activities within structures. The typical frequency range for structural geophones generally falls between 1 Hz and 100 Hz. This range is sufficient to capture the vibrations caused by various sources such as traffic, machinery, human activities, and seismic events.
  1. Low-Frequency Range (1 Hz - 10 Hz):
      • Use Cases: Capturing long-period vibrations such as those from distant earthquakes, large-scale structural movements, and slow oscillations in large structures like bridges and tall buildings.
      • Example: 4.5 Hz geophones are commonly used in structural health monitoring to capture a wide range of vibration frequencies.
  1. Mid-Frequency Range (10 Hz - 50 Hz):
      • Use Cases: Capturing more localized vibrations such as those from human activities, machinery, and traffic.
      • Example: 10 Hz geophones are widely used for general structural monitoring, providing a balance between sensitivity and frequency range.
  1. High-Frequency Range (50 Hz - 100 Hz):
      • Use Cases: Capturing high-frequency vibrations such as those from impact events, high-speed machinery, and structural responses to short-duration forces.
      • Example: Higher frequency geophones (e.g., 100 Hz) are less common but can be used in specific applications requiring detailed monitoring of high-frequency vibrations.

Practical Examples of Structural Geophones

  1. Geosense GS-11D:
      • Frequency: 4.5 Hz
      • Applications: General structural health monitoring, capturing a broad range of frequencies including lower-frequency structural movements.
  1. SM-24 Geophone:
      • Frequency: 10 Hz
      • Applications: Commonly used in both geotechnical and structural applications for general vibration monitoring.
  1. RSM-2000 Geophone:
      • Frequency: 10 Hz
      • Applications: Suitable for structural monitoring applications, providing good sensitivity across a broad frequency range.

How to Read a GeoPhone with ESP32

To interface commercially available geophones with an ESP32, you generally use the ADC (Analog-to-Digital Converter) interface. Geophones typically output an analog voltage signal that represents the detected vibrations, which needs to be sampled and digitized by the ESP32's ADC.

Using ADC Interface

  1. Analog Signal:
      • Geophones output analog signals that vary with the detected vibrations. The signal is typically a small voltage that needs to be sampled by the ADC of the ESP32.
  1. Connecting Geophone to ESP32 ADC:
      • Connect the geophone's output to one of the ADC input pins on the ESP32.
      • Ensure proper grounding and shielding to minimize noise.
      • You might need to amplify the signal from the geophone if it is too small for the ESP32's ADC range.

Example Setup

Components:

  • ESP32: Microcontroller with built-in ADC.
  • Geophone: Analog output sensor.
  • Signal Conditioning Circuit: Amplifier and filter (optional, depending on the geophone's output).

Basic Connection Diagram:

Sample Code for Reading ADC

Here's an example of how to read an analog signal from a geophone using the ESP32's ADC:

Considerations

  1. Signal Amplification:
      • Depending on the geophone's output, you might need an operational amplifier to amplify the signal to a level suitable for the ESP32's ADC.
      • Ensure the amplified signal stays within the ADC's input range (typically 0 to 3.3V for ESP32).
  1. Filtering:
      • Use appropriate filters to remove noise and unwanted frequencies from the geophone signal before it reaches the ADC.
  1. Sampling Rate:
      • Choose an appropriate sampling rate based on the geophone's frequency response and the type of vibrations you are monitoring. Ensure the ESP32's ADC sampling rate is sufficient to capture the details of the signal.

Alternatives: UART and I2C

While ADC is the most direct method for interfacing with analog geophones, some geophones may come with built-in digital output capabilities using interfaces like UART or I2C. These typically include additional circuitry and might be marketed as digital geophones or accelerometers.
  1. UART:
      • Used for digital geophones that output data in serial format.
      • Requires parsing of serial data to extract vibration information.
  1. I2C:
      • Used for digital geophones or accelerometers with I2C interfaces.
      • Requires addressing and communication setup specific to the sensor.

Summary

For most commercially available analog geophones, the ADC interface on the ESP32 is the appropriate choice. Proper signal conditioning, amplification, and filtering may be required to ensure accurate readings. If the geophone has a digital output, you might use UART or I2C interfaces, depending on the sensor's specifications.

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