Portable Instrumentation

A datalogger (also know as data acquisition system) is piece of electronic equipment which converts an input into a digital time series representation. Immense care should be taken when setting up and programming a datalogger. It is highly recommended that only experienced users program their own dataloggers and all others should consult an EPIC staff member for assistance.

While specific procedures and programming details will vary between the various types of dataloggers, there are several things that hold true when working with any datalogger.

The datalogger should be:

• Installed in a secure location
• Protected from moisture
• Supplied with reliable and sufficient power
• Programmed with the correct recording parameters
• Connected properly to the sensor
• Receiving accurate timing (from GPS)
• Recording data onsite to non-volatile memory

The facility currently has three- and six-channel dataloggers for PI projects.

The NSF NGF additionally has 3-channel nodes available for lone.

The FairfieldNodal ZLand 3C is a compact all-in-one 3-channel sensor & datalogger with onboard GPS timing, and a self contained power supply. Originally designed for use in large N industry deployments, it has been adopted by the academic community as a useful sensor for both active and short-term passive deployments.

Unlike other sensors & dataloggers at EPIC, use of the ZLand 3C requires a deployment plan to be filed in advance with EPIC for handheld unit pre-programming.  Likewise, the units must be sent back to EPIC for data offload.

Specifications:

• This 3-channel all-in-one sensor + datalogger has a corner frequency of 5Hz and a 24 bit ADC
• Power source: Lithium ion battery with ~35 day lifespan at 500sps continuous recording
• Physical Size: 6.4in x 4.6in with additional 4.6in central spike
• Weight: 6.2lbs
• Sample rate: 250, 500, 1000, or 2000 sps
• Storage capacity: 32GB (500sps continuous record ~=388.8Mb/day)

Please visit the Station Builder Tool to see the specific instrument models available for use. 

Seismometers are instruments that measure and record motions of the ground, including those of seismic waves generated by earthquakes, nuclear explosions, and other seismic sources. Records of seismic waves allow seismologists to map the interior of the Earth, and locate and measure the size of these different sources.

The EPIC supports the following types of seismometers:

• Broadband Sensors - are three-component seismometers capable of sensing ground motions over a wide frequency band. These sensors are most-often used in passive experiments.The flat-to-velocity portion of the bandwidth is generally about 0.01 Hz (100 sec) to 25Hz. With sufficient signal, however, the 120-sec velocity transducers in the EPIC fleet can record signals with periods many thousands of seconds long, such as earth tides.
• Intermediate Sensors - are three component seismometers with corner periods in the 30- to 40-second range (distinct from the 120- to 240-second range of EPIC's truly broadband fleet). These sensors, like their broadband cousins, are capable of sensing ground motions of much longer period than their corner periods, if the long-period amplitudes are sufficient.
• Short-Period Sensors - are rugged three-component seismometers that cover higher-frequency bands (usually 1 Hz to 100+ Hz). These sensors are used in both passive and active-source experiments. The sensors, themselves, can be either feedback seismometers requiring power or conventional, passive seismometers requiring no external power.
• High-Frequency Sensors - are very rugged seismometers that cover even higher frequency bands (e.g. 4.5 Hz to 100+ Hz).  These sensors are most-often used in active-source experiments and are often referred to as geophones.
• Accelerometers - also known as strong-motion sensors, are designed to measure the large amplitude, high frequency seismic waves typical of large local earthquakes, and operate in the frequency band 0 Hz to 100+ Hz.

Overview

Regardless of the type of datalogger and sensor, the one constant they all need is power.

Batteries

Because of the relative isolation of seismic and GNSS stations the most common power source is a battery. Batteries come in two main types: primary and secondary. Secondary batteries are rechargable and primary batteries are used once then discarded.

Most experiments that utilize dataloggers (seismic and GNSS stations, ERT, MT, GPR) will use deep cycle lead-acid batteries. The size and capacity of the lead-acid battery will vary with datalogger type, sensor type, telemetry, solar panel size, and geographic location.

Smaller devices such as kinematic GNSS and seismic nodes often have rechargeable internal batteries such as lithium ion.

At least 3 months before a long-term experiment is scheduled to go in the field, you should consult with EPIC personnel to discuss the power requirements for your experiment.

Power Box

The power box is a plastic enclosure which houses the solar charge controller. This box is what routes power from the solar panels into the battery and power from the battery to the datalogger and sensor.

Solar Equipment

To keep a long term experiment powered some solar equipment will be required. The solar equipment refers to the combination of solar panel and a solar panel mount. Having the proper sized solar panel and proper placement is one of the most important aspects of a seismic station installation because without power you have nothing.

The Propelled Energy Generator, model: PEG-40Kg

A PEG 40Kg Propelled Energy Generator, manufactured by R.T. Clark Companies, Inc. is available from the EPIC. The system is light weight, and highly portable, and is designed to easily mount onto a truck or SUV hitch. Seismic energy is produced when a large hammer mass weight is propelled by an elastomer band (i.e. a very large rubber band) onto an impact plate, producing an impact frequency range of 10-250Hz. The source is controlled with a hand held motor controller,  and can operate in single cycle or continuous cycle mode. The device is powered by a 12V large capacity battery (car battery). 

Magnetotelluric (MT) methods are used to produce conductivity models of the crust and upper mantle through the recording of geoelectric and geomagnetic field variations at the Earth's surface. Depending on the period of the recordings, these methods can provide results from a few hundred meters depth (short period) to 30 km or deeper (long period). Conductivity is a physical property, which is complementary to seismic velocity, and which is very sensitive to the presence of fluids. When seismic and MT data sets are measured together, the additional data can dramatically improve determinations of the structure of the crust and mantle.

EPIC currently maintains Sensors & Software Noggin GPR Systems equipped with a SmartCart configuration. These systems offer onboard GNSS/GPS positioning*, data acquisition programming, and preliminary data interpretation capabilities. Operators can perform both line-scan and grid-scan data collection, and the intuitive interface supports quick setup, real-time waveform viewing, and on-the-fly depth estimations. Each GPR system is compatible with EPIC’s Emlid RTK GNSS equipment, enabling centimeter-level positioning accuracy for projects that require precise geolocation. Standard GNSS accuracy (several meters) is sufficient for many applications, but RTK corrections can be applied via a base station or cellular link—just ask EPIC staff for assistance or to reserve the appropriate accessories.

Processed onboard data can be visualized as depth versus position along a line, or as a slice view of grid data. For more in-depth post-acquisition processing and interpretation of the data, Sensors & Software EKKO Project GPR software access is also available from the EPIC.

The Noggin systems  support four frequency antenna configurations: 1000 MHz, 500 MHz, 250 MHz, and 100 MHz for near surface GPR investigations, expanding the bandwidth and allowing for tailored depth and resolution trade-offs across applications. The addition of the 100 MHz antenna significantly improves performance in environments where greater depth penetration is required.

1000 MHz: Highest resolution, shallowest depth—ideal for fine, near-surface detail

500 MHz & 250 MHz: Balance between depth and resolution—commonly used in most field scenarios

100 MHz: Newest addition, stronger signal with the greatest depth of penetration, suitable for deeper subsurface features

Example uses include hydrology, engineering, archaeology, forensics, and educational projects. 

*Uncorrected GNSS/GPS locations have an accuracy of several meters, which is often sufficient for GPR surveying, depending on the use case. If you would like more accurate (cm-scale) GNSS/GPS locations, request an Emlid base station along with the receiver automatically included with the GPR. The base station will be able to send corrections to the GPR’s receiver. Or ask EPIC staff how to enable cellular corrections to the GPR’s receiver.

Global Navigation Satellite System (GNSS) receivers sense incoming signals from the USA’s Global Positioning System (GPS) satellites and other constellations (GLONASS, Galileo, BeiDou, etc.). With signals from four or more satellites, the receivers use trilateration to determine a position.

Static GNSS/GPS

Some GNSS receivers are designed for long-term or permanent installation at a single (static) location. With appropriate data durations, data processing, and instrument monumentation, the positions from these receivers can be used to determine mm-scale 3D velocities and potentially a variety of other products related to site and atmospheric conditions.

Kinematic GNSS/GPS

Other receivers are designed for mobile (kinematic) surveying. A mobile “rover” receiver receives location corrections from a local base station via a radio or cellular connection so that the accuracy can be increased from meters to centimeters of uncertainty. The rovers are typically deployed on survey poles, whereas the base station is on a tripod over a known point.

Kinematic GNSS receivers are available for both research and educational uses.

EPIC has SuperSting R8 systems from Advanced Geosciences, Inc for electrical resistivity tomography (ERT) studies.

Available sets of cables include: sets of 56-electrodes at 2-meter spacing, and sets of 112-electrodes at 6-meter spacing.