High Perfomance Broadband Seismometer - REF TEK 151B-120

Posted on December 5th, 2016 by vapro

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  • High performance broadband seismometer
  • Low self-noise over a wide bandwidth
  • Portable design
  • Low power consumption
  • Force-balance electronic feedback
  • Robust mass locking mechanism
  • Easy installation


The 151B series Broadband Seismometer, “Observer”, is a force-balance feedback sensor available with frequency bandwidth 0.0083 Hz (120 sec) – 50 Hz. The 151B Observer contains three independent sensors (one vertical and two horizontal) with built-in electronic feedback circuit, control and power conversion circuits, featuring low noise, large dynamic range and easy installation and use.

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 which are located on the seismometer’s chassis.

The 151B Observer has a built-in mass zero-position adjusting mechanism to perform automatic mass adjustment. As soon as the seismometer is powered it checks the zero position of each component’s mass and automatically adjusts the zero position if needed.

The 151B Observer is a low noise seismometer (see Power Spectral Density plot below). The low self noise performance makes the 151B-120 an ideal seismometer for local, regional, and global seismicity studies in different installation configurations, including observatory and portable, surface and posthole applications.

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

Sensor Type Triaxial, orthogonal
Feedback Force balance with capacitive displacement transducer
Frequency Response 0.0083 Hz (120 sec) – 50 Hz, Model 151B-120
Sensitivity 2000 V/m/s
Full Scale Output +/- 20 V peak-to-peak differential
Dynamic Range >140 dB @ 5Hz
Output Impedance <100 Ohms
Calibration Coil resistance 1,000 Ohms, sensitivity: 10 m/s2/A
Leveling Two Integrated bubble levels. Three adjustable leveling feet with locknuts
Mass Position Remote monitoring and adjusting zero-point using 3 independent voltage outputs
Mass Locking Mechanical lock-unlock mechanism accessible on outside of the case
Distortion Total distortion less than -80 dB
Cross Axis Coupling < 1%
Mechanical Zero No need for adjustment within ambient temperature fluctuation +/- 20C
Power-Fail Protection Built-in
Signal Overload Protection Built-in
Auto-recovery Time Full operation recovery within 10 minutes after either power fail or signal overload
Power Input +12 VDC (9V to 18 VDC)
Operating Temperature -20o C to +60o C
Power Consumption ~ 1.1 W
Water Tight Integrity IP67 for outdoor use and immersion resistance
Case Aluminum, Powder Coated
Dimensions Diameter: 9.45 ” (24 cm); Height: 10.6 ” (27 cm)
Weight 26.4 lbs (12 kg)
Alignment Removable orientation N/S pins screw into the base (brass for N, silver for S)
Lightning Protection Built-in
Low Spurious Resonance Higher than 100 Hz
Damping 0.7 of Critical
Linearity Better than 1% of full scale
Accessories (optional) Rugged transportable hardigg case. Flexible insulation bag

151B Standard Observer Kit

The 151B Standard Observer kit includes: a) Seismometer; b) T-type Allen wrench key for leveling; c) Aluminum carrying case with pre-cut foam; d) orientation pins

151B Standard Observer Kit

151B Optional Ruggedized Transport Case

151B Optional Ruggedized Transport Case

The 151B Observer is available with an optional ruggedized transportation case and thermal insulation bag.

The 151B Observer’s transportation case is a ruggedized, durable, lockable case with handles and removable casters, designed for multiple shipments by any means of transportation in a harsh environment.

The transportation case has pre-cut foam to house the 151B Observer with carrying case, removable casters and accessories, including sensor cable and thermal insulation bag.

The 151B Observer’s thermal insulation bag is fabricated from Microfleece material with primaloft insulation, providing protection from wind and daily temperature fluctuations in the vault to insure the highest quality data.

151B Optional Ruggedized Transport Case


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

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