REF TEK 151B-120 Observer, High Performance Broadband Seismometer


  • Low self-noise over a wide bandwidth
  • Low power consumption
  • Force-balance electronic feedback
  • Robust mass locking mechanism
  • Portable, and easy installation


  • Local and regional seismic networks
  • Broadband surface or posthole installation
  • GSN installation


The Observer broadband seismometer is used worldwide for local, regional and global seismicity studies. It contains one vertical and two horizontal independent sensors with built-in electronic feedback circuit and features low noise with a large dynamic range.  The low self-noise performance makes the Observer an ideal seismometer for seismicity studies in different installation configurations, including observatory and portable, surface and posthole applications. The Observer broadband seismometer is a force-balance feedback sensor available with frequency bandwidth 0.0083 Hz (120 sec) – 50 Hz.

The 151B Observer has built-in leveling and mass lock/unlock facilities. The leveling mechanism includes two bubble levels, three adjustable feet and three locknuts, located on the chassis.

A mass zero-position adjusting mechanism performs automatic mass centering. As soon as the seismometer is powered it checks the zero position of each component’s mass and automatically adjusts the zero position when required.

Noise Model for the 151B

Noise Model for Ref Tek 151B

Ringler, A. & Hutt, C. (2010, November-December). Self Noise Models of Seismic Instruments. Seismological Research Letter, 81(6), 972-983


151B Standard Observer Kit

The 151B Standard Observer kit includes: 

  •  Seismometer;
  •  T-type Allen wrench for leveling from above the unit;
  •  Aluminum carrying case with pre-cut foam;
  •  Orientation pins

151B Observer Ruggedized Transport Case and Thermal Bag – Optional

151B Optional Ruggedized Transport Case

Designed for multiple shipments, this transport case is rugged, practical, durable and lockable.  The Thermal insulation bag has primaloft insulation, providing protection from wind and daily temperature fluctuations, insuring high quality data collection.


151B Optional Ruggedized Transport Case


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