Model 151-30 / 151-60 /151-120
Features:
- 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
Applications:
- Local and Regional
- Broadband Surface or Posthole Installation
- GSN Installation
The 151 series Broadband Seismometer, “Observerâ€, 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 “Observer†with with frequency bandwidth 0.033 Hz (30 sec) - 50 Hz is available upon request. The 151 “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 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 (see photo below). The Observer has 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. Monitoring and adjustment of the mass can also be performed via the 130 family High Resolution Recorders using Sensor Control Board, RT527-B01. The Observer is a low noise seismometer (see below Power Spectral Density plot). The low self noise performance makes the 151-120 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 REF TEK 151
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Sensor Type
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Triaxial, orthogonal
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Feedback
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Force balance with capacitive displacement transducer
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Frequency Response
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0.0083 Hz (120 sec) - 50 Hz (see diagram in manual), Model 151-120
0.0166 Hz (60 sec) - 50 Hz, Model 151-60
0.033 Hz (30 sec) - 50 Hz, Model 151-30 (optional upon request)
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Sensitivity
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2000 V/m/s
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Output Signal
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+/- 20 V peak-to-peak differential
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Dynamic Range
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>140 dB @ 5Hz
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Output Impedance
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<100 Ohms
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Calibration
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Coil resistance 1,000 Ohms, sensitivity: 10 m/s2/A
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Leveling
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Two Integrated bubble levels. Three adjustable leveling feet with locknuts
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Mass Position
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Remote monitoring and adjustable zero-point using 3 independent voltage outputs
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Mass Locking
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Mechanical lock/unlock on outside of the case
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Distortion
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Total distortion less than -80 dB
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Cross Axis Coupling
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< 1%
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Mechanical Zero
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No need for adjustment within ambient temperature fluctuation +/- 20o C
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Power-Fail Protection
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Built-in
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Signal Overload Protection
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Built-in
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Auto-recovery Time
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Full operation recovery within 10 minutes after either power fail or signal overload
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Supply Voltage
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9 to 18 VDC
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Operating Temperature
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-20o C to +60o C
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Power Consumption
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~ 1.1 W
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Water Tight Integrity
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IP67 for outdoor use and immersion resistance
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Case
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Aluminum, Powder Coated
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Dimensions
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Diameter: 9.45 " (24 cm); Height: 10.6 " (27 cm)
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Weight
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26.4 lbs (12 kg)
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Connector
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PTO2A 14-19S
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Alignment
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Removable orientation North(brass) / South(silver) pins screw into the base
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Accessories (optional)
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Rugged transportable hardigg case. Flexible insulation bag (P/N 151-9800)
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Standard Observer KitThe 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 
Optional Ruggedized Transport CaseThe Observer is available with an optional ruggedized transportation case and thermal insulation bag. The 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 151 Observer with carrying case, removable casters and accessories, including sensor cable and thermal insulation bag. The Observer 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. 
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