Trimble REF TEK 151B Series

  • 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
Product Resources
  • Overview

  • Noise Model for the 151B

  • 151B Accessories

  • Applications

The 151B series Broadband Seismometer, “Observer”, is a force-balance feedback sensor available with frequency bandwidth 0.0083 Hz (120 sec) - 50 Hz, and 0.016 Hz (60 sec) - 50 Hz flat to velocity. 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 next tab for Power Spectral Density plot). 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

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


Sensor Type

Triaxial, orthogonal


Force balance with capacitive displacement transducer

Frequency Response

0.0083 Hz (120 sec) - 50 Hz, Model 151B-120
0.0166 Hz (60 sec) - 50 Hz, Model 151B-60


2000 V/m/s

Full Scale Output

+/- 20 V peak-to-peak differential

Dynamic Range

>140 dB @ 5Hz

Output Impedance

<100 Ohms


Coil resistance 1,000 Ohms, sensitivity: 10 m/s2/A


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


Total distortion less than -80 dB

Cross Axis Coupling

< 1%

Mechanical Zero

No need for adjustment within ambient temperature fluctuation +/- 20C

Power-Fail Protection


Signal Overload Protection


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


Aluminum, Powder Coated


Diameter: 9.45 " (24 cm); Height: 10.6 " (27 cm)


26.4 lbs (12 kg)


Removable orientation N/S pins screw into the base (brass for N, silver for S)

Lightning Protection


Low Spurious Resonance

Higher than 100 Hz


0.7 of Critical


Better than 1% of full scale


Free-running Oscillator 

Accessories (optional)

Rugged transportable hardigg case. Flexible insulation bag

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

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