Seismometers - Sensors

A selection of 1Hz seismometers for earthquake recording, featuring single component, three component, and borehole versions.

LE-3D/20s Seismometer Sensor

Low frequency seismometer with response down to 20 seconds. For those interested in "classical" regional earthquake seismology, or in the low frequency grumbling of volcanoes, this fills a niche between short period and "real broadband".

This is the latest addition to the product line, further boosting low frequency response down to 20 seconds. For those interested in "classical" regional earthquake seismology, or in the low frequency grumbling of volcanoes, this instruments fills a niche between short period and "real broadband".

While physically identical to LE-3D/5s (except for the different paint color), it is a fundamentally different instrument under the hood. In order to bring a physical 2 Hz electrodynamic geophone to behave like a 20 sec seismometer (remember those clumsy yet delicate beasts? You barely touched them, and the mass would shift out of whack!), considerable electronic wizardry needs to be applied. To some extent, this comes at a price - increased power (but still within very reasonable limits). However, many of the qualities that have made these seismometers the practitioner's favorites for more than a decade are present in this instrument. Compared to "true broadband" sensors, the most salient advantages are much faster startup time (the instrument will output meaningful results in less than a minute after power-up!) and drastically reduced sensitivity to temperature or pressure fluctuations. Since there is no physical long-period element inside, nothing will respond to daily temperature drift, or to the sudden air draught of a door being shut.

Technical Details:

• Power Supply: 10...16V DC, unstabilised
• Power Consumption: approx. 50mA @ 12 V DC, max. 100 mA (when full scale output is present)
• Output Voltage: 1000 V/m/s, precisely adjusted on all components
• Damping: 0.707 critical (internal damping; independent of datalogger input resistance)
• Dimensions: 195 mm diameter, 165 mm height
• Weight: including 1.5 m cable and Cannon KPT connector) 6.5 kg
• Temperature range: -15...+35°C
• Optional temperature range: (specify when ordering) 0...+50°C
• Housing: Painted aluminum, splash proof, with level adjustment feet and water bubble level control
• Eigenfrequency: 0.05 Hz
• Upper corner frequency: > 40 Hz
• RMS noise at 1 Hz: < 2 nm/s

LE-3D/5s Seismometer Sensor

LE-3D/5s is the sensor of choice for a wide variety of field and observatory tasks - being still portable with flat velocity response down to 5 seconds while still preserving basic fieldworthy qualities such as ruggedness and portability.

This instrument is the runner-up in terms of popularity - it provides flat velocity response down to 5 seconds while still preserving basic fieldworthy qualities such as ruggedness and portability. After its introduction in late 1990, it quickly gained acceptance among those requiring a little bit of extra low frequency response.

LE-3D/5s is the sensor of choice for a wide variety of field and observatory tasks - being still portable, it will allow you to go places where a broadband sensor just won't do the job. If space and weight constraints prevail, LE-3D/5s will help you meet them. It is not only the dimensions and weight of the sensor proper that count - do not forget to take power requirements into account. In this department, the LE-3D/5s leaves broadband seismometers in the dust. At only 100mW, LE-3D/5s won't require its own truck battery even for a long-term deployment. As an example, a 20 Ah battery (which is still easily handled) will last up to 100 days!

But do not believe that this noteworthy power consciousness will incur a significant performance penalty - the noise level of this sensor (approx. 1 nm/s RMS at 1 Hz) is such that it can be used in most low-noise sites without problems.

Most of the salient points in favor of the 1 Hz seismometers are equally applicable here:

• Compact and lightweight
• Rugged
• Sheer simplicity; true plug-and play operation
• All sensors calibrated to identical output voltages; no need to keep records of which sensor has been connected to which datalogger
• Low noise, low power (typically 3 mA per component @ 12 V DC)
• Dynamic range > 120 dB
• Comparatively insensitive to improper leveling
• No mass lock, mass center, control box, or other contraption required; can be transported in any orientation
• Proven long-term stability; well over ten years of field experience

• Power Supply: 10...16V DC, unstabilised
• Power Consumption: approx. 10mA @ 12 V DC
• Output Voltage: 400 V/m/s, precisely adjusted
• Damping: 0.707 critical (internal damping; independent of datalogger input resistance)
• Dimensions: 195 mm diameter, 165 mm height
• Weight: including 1.5 m cable and Cannon KPT connector) 6.5 kg
• Temperature range: -15...+35°C
• Optional temperature range: (specify when ordering) 0...+50°C
• Housing: Painted aluminum, splash proof, with level adjustment feet and water bubble level control
• Eigenfrequency: 0.2 Hz
• Upper corner frequency: > 40 Hz
• RMS noise at 1 Hz: < 1 nm/s

LE-xD 1Hz Seismometer Sensor

A 1Hz seismometer available as either single componet, vertical or horizontal, or 3 component unit. A rugged, low power, field proven seismometer.

These are the workhorses of the scientific product line. Originally available in a blue rectangular housing (known for a long time as the "LE-3D classic", now out of production), hundreds of these sensors are in daily duty all over the world. The current model (shown below) comes in a cylindrical stainless steel housing and is called LE-3Dlite. Additionally, single component versions for vertical or horizontal use are available, aptly named LE-1D/V and LE-1D/H.

Users are attracted by these unique features that set these sensors miles apart from their mechanical predecessors:

• Extremely compact and lightweight
• Rugged
• Sheer simplicity; true plug-and play operation
• All sensors calibrated to identical output voltages; no need to keep records of which sensor has been connected to which datalogger
• Low noise, low power (typically 3 mA per component @ 12 V DC)
• Dynamic range > 120 dB
• Comparatively insensitive to improper leveling
• No mass lock, mass center, control box, or other contraption required; can be transported in any orientation
• Proven long-term stability; well over ten years of field experience

The following table shows the relevant technical parameters for both the single and the three component versions of the 1 Hz seismometers:

	LE-1D/H and LE-1D/V	LE-3Dlite
Power Supply	10...16V DC, unstabilised	10...16V DC, unstabilised
Output Voltage	400 V/m/s, precisely adjusted	400 V/m/s, precisely adjusted on all components
Damping	0.707 critical (internal damping; independent of datalogger input resistance)	0.707 critical (internal damping; independent of datalogger input resistance)
Dimensions	85 mm diameter, 55 mm height	95 mm diameter, 65 mm height
Weight, including 1.5 m cable and Cannon KPT connector)	1.1 kg	1.8 kg
Temperature range	-15...+35°C	-15...+35°C
Optional temperature range (specify when ordering)	0...+50°C	0...+50°C
Housing	Stainless steel, matted surface, splash proof, with level adjustment feet and water bubble level control	Stainless steel, matted surface, splash proof, with level adjustment feet and water bubble level control
Eigenfrequency	1 Hz	1 Hz
Upper corner frequency	> 80 Hz	> 80 Hz
RMS noise at 1 Hz	< 3 nm/s	< 3nm/s