To help expedite the troubleshooting process, please gather the following information, if possible, before contacting Technical Support:

• The Model and Serial Number of the malfunctioning equipment and any other equipment used in conjunction with it (e.g. sensor, readout, datalogger, etc.)
• Date the equipment was installed
• Date the issue arose
• What software program is being used to view the data?
• Have any splices or repairs been performed on the cable? If yes, what type?
• Do the factory zero readings closely match the field zero readings?
• Are other gauges installed in the same borehole or connected to the same datalogger? If yes, are those gauges functioning correctly?
• Has the faulty gauge been tested using another readout or datalogger?
• Are there any sources of electrical noise near the instrument or cable (e.g., generators, pumps, high-power utility lines, etc.)?
• Take pictures of the installation, including the wiring inside the datalogger or readout.

• Download our helpful Technical Support Checklist (pdf form)›

The design process of a Multi-Point Borehole Extensometer (MPBX) can be complex. Many critical details must be taken into account to ensure the design is successful. Several factors can influence the design, including borehole diameter, subsurface material, anchor type, range of movement, measurement points, and head assembly location.

Borehole Diameter

• The borehole must be large enough to accommodate the head assembly collar and standpipe (if used), especially if the head will be recessed.
• Some anchor types have specific minimum and maximum borehole size tolerances.
• If the extensometer will be installed through an auger or within a cased borehole, the casing or auger’s inside diameter must also be considered.

Subsurface Material

• The subsurface material of the borehole will directly impact the anchor type and the expected range of movement.
• The measurement zones (anchor locations) are determined by understanding subsurface conditions.
• In some cases, the appropriate anchor depths are identified in the field after drilling the borehole or access hole.
• If the material is compressible and large displacements are expected, it may be necessary to include slip couplings in line with the rod sheathing, especially with rigid PVC tubing.

Anchor Type

• The type of anchors used should be considered based on the orientation of the borehole and the type of subsurface material expected.
• Borros anchors are best suited for soft, compressible soil.
• Groutable anchors, constructed from steel reinforcing bar lengths, are the preferred option for installation in downward-directed boreholes easily filled with cement grout.
• Hydraulic bladder anchors can be installed in boreholes oriented in any direction, so long as the subsurface material is competent rock. They are particularly beneficial in boreholes that are fractured, oriented upwards, or challenging to grout.

Range of Movement

• The range of movement impacts the height of the head assembly.
• This is especially true for extensometers utilizing electrical displacement transducers, which may require a head assembly height of 0.5 to 1 m (2 to 3 feet).
• Rigid PVC tubing can accommodate some elongation or compression; however, when a large amount of displacement is expected, it is best to incorporate a slip coupler to reduce the potential for damage to the tubing.

Measurement Points

• The deepest anchor typically serves as the fixed datum point for the extensometer system and should be located in soil or rock that will not be deforming or displaced.
• If the application does not allow the deepest anchor to act as the reference point (e.g., tunnel or underground opening below installation), the head assembly can be used instead.
• When the head assembly is used, it must be surveyed periodically to establish an absolute point of reference.
• The number of anchor points often influences the head assembly collar and standpipe size and whether it will be read manually or with electrical displacement transducers (or a combination thereof).

Head Assembly Location

• Where clearance is not an issue, the head assembly can protrude from the borehole.
• Protruding head assemblies need to be protected from mechanical damage.
• Protection from temperature fluctuations is also needed if they contain displacement transducers, which are susceptible to temperature effects.
• If there isn’t enough clearance for the head assembly to protrude, it must be recessed below ground level.
• In some cases, the head can be lowered completely into the borehole.
• If this is not possible, an over-core will be required to recess the head. Over-coring can offer more space to work when it is time to install the transducer mount and transducers. It can also accommodate large collar hardware such as a flange.
• For deep-recessed installations, special tools may be needed to reach the tube mount for installation and adjustment of the transducers.

For more information about Multi-Point Borehole Extensometer design, refer to the Model 1100 instruction manual or contact GEOKON.

Initial zero readings are very important in helping ensure improved accuracy with your measurements.

An initial zero reading establishes a baseline measurement, from which all subsequent data values are calculated.

In general, the initial zero reading is obtained by taking a measurement of the instrument on-site, prior to installation. Use of this field zero reading, instead of using the factory zero reading, will improve the accuracy of your calculated data values. On-site zero readings should closely coincide with the factory zero reading provided on the instrument’s calibration report (after any necessary temperature and barometric pressure corrections have been made). There are several different ways of taking an initial zero reading, and the exact steps involved vary by instrument. Consult the instruction manual provided with the instrument for specific instructions.

Has the reading from a GEOKON vibrating wire instrument become unstable?

Has the instrument stopped working altogether?

This may be a sign that the cable has been broken, cut, or crushed. A quick and easy way to determine if the cable has been damaged is to use an ohmmeter to measure the resistance between the gauge leads. The expected resistance for the various wire combinations can be found on the VW Sensor Resistance Worksheet.

• If the resistance is very high (>1 megohm) or infinite, the cable is probably broken or cut.
• If the resistance is much lower than the gauge resistance specified in the instruction manual, the gauge conductors may be shorted.

Cable resistance should be taken into account, especially for long cables. Cable resistance for 22 AWG wire is approximately 14.7Ω per 1000 ft.(48.5Ω per km). Multiply this factor by two to account for both directions.

The internal thermistor can be checked in a similar manner by connecting the thermistor leads of the instrument to the ohmmeter. Standard thermistors have a resistance of 3,000Ω at 25 °C. High temperature thermistors have a resistance of 10,000Ω at 25 °C. For other temperatures, consult the thermistor resistance to temperature conversion tables in the instruction manual.

A constantly fluctuating vibrating wire reading may be caused by electrical interference.

Common sources of electrical interference include, generators, motors, arc welding equipment, high voltage lines, etc. If possible, move the instrument cable away from power lines and electrical equipment or install electronic filtering.

Another common cause of reading instability is a misconnection between the instrument conductors and the readout/datalogger, or incorrect readout/datalogger settings. Consult the instruction manual provided with the instrument to verify that all gauge conductors have been properly connected, and that the readout or datalogger has been set up correctly for the type of gauge being read. (If using a datalogger to record readings automatically, make sure the swept frequency excitation settings are correct.)

If the above suggestions do not correct the problem, the readout or datalogger may be malfunctioning. Try connecting a different gauge to see if the problem persists.

How do I choose the appropriate pressure range?

When selecting piezometer ranges, you should consider the pressure resulting from the height of water above it (approximately 1 psi per 2.3 ft. of water/1 kPa per 0.10 m of water) as well as the pressure resulting from any grout that will be placed over it (approximately 1.7× the weight of water). Excessive pressure can potentially over-range and damage the sensor and should be avoided. If grout pressure exceeds the pressure range of the piezometer, stage grouting can be considered, or a piezometer with a higher pressure range can be used (being mindful of the corresponding loss in sensitivity).

How “rugged” are VW piezometers?

VW piezometers are very reliable and have been shown to perform well over extended periods of time, even in harsh environments. The sensors are rugged and capable of withstanding nominal shock loads; their signals can be transmitted via cables over long distances (2 km+) without degradation.

What if I over-range the piezometer?

VW piezometers can withstand certain amounts of over-ranging. The magnitude ultimately depends on the piezometer type, but as a rule of thumb, over-ranging should not exceed 150% of the specified range. Beyond 100% of full-scale range, there can be a slight loss in accuracy, but permanent damage is rare below 150%. If in doubt, contact the factory.

How do I know if a piezometer is reading correctly?

To test if a piezometer is working correctly (after a shock impact, for instance), perform an on-site spot check to verify that the zero reading aligns with the factory zero reading. If the on-site zero reading—after corrections for temperature, barometric pressure, and elevation are made—falls within approximately 50 “digits” (1 digit = frequency squared/1000) of the factory zero reading, then the piezometer can be considered to be working correctly. If the reading is off by more than 60 digits, the sensor may still perform correctly; however, the factory should be contacted for further guidance.

How can I protect the piezometer from freezing?

Foam plug inserts installed in piezometer tips can significantly reduce the potential for ice damage in freezing conditions (contact the factory for further details).

A GeoNet Network consists of a certain number of loggers and one gateway.

• Loggers:
  • Collect data from sensors (piezometers, strain gauges, etc.)
  • Forward the collected data to the gateway
  • Relays data from/to other loggers as necessary to reach the gateway

• Gateway:
  • Controls the network
  • Central collection point for all data

GeoNet operates on a self-healing, mesh radio network.

To create the best radio environment possible, follow these guidelines:

• Always mount GeoNet devices so the antenna is pointing up.
• Create as much clear space around the antenna as possible and remove any nearby obstructions.
• A minimum mounting height of six-feet is recommended.
• Common mounting mistakes include:
  • Not enough clear space around the antenna
  • Mounting devices horizontally
  • Placing the device inside an enclosure
  • Metallic objects nearby
  • Mounting on mesh fencing or surrounding the device with mesh fencing

GeoNet devices can only communicate with other devices that are set to the same radio channel and are within range of their radio signal.

• All GeoNet devices are set to operate on the same channel at the factory
• Channels only need to be configured if multiple networks will be operating within radio range of one another

GeoNet loggers can communicate with the gateway over greater distances, and work around obstacles, by using other loggers as repeaters.

• Each transmission from logger to logger, or from logger to gateway is known as a “Hop”
• Up to four hops can be made between a logger and the gateway
• The network will automatically find the ideal path between each logger and the gateway

There are two modes of network operation: Deployment mode and Normal mode.

• Deployment Mode:
  • Allows Loggers to be quickly added to a network and verified
  • Must be used when setting up a network or making changes to the network (adding Loggers, changing batteries, resetting a device, etc.)
  • Indicated by the LEDs on the gateway flashing every 10-15 seconds
  • Automatically activated when the gateway is powered on
  • Active for 60 minutes by default (the deploy period can be changed using Agent software)
  • Can be reactivated/reset by pressing the status button on the gateway (may take up to 3 minutes to take effect)
  • Though deployment mode can be activated in Agent software, it is best practice to physically press the status button on the gateway

• Normal Mode:
  • Less battery usage than Deployment mode
  • Default mode of operation when not in Deployment mode

No Power:

• Loggers and Local Gateways:
  • Check the batteries to make sure they are properly installed
  • Replace batteries if they are depleted
  • Make sure the power switch is set to the correct battery type: lithium or alkaline
• Cellular Gateways:
  • Make sure the AC adaptor or other external power source is connected correctly (Cellular Gateways must have an external power source)
  • Make sure the power switch is set to “INT BATTERY” (the EXT BATTERY position is only used for subpolar climates: see the manual for more information)

Logger will not join the network:

• Make sure deployment mode is active (indicated by one or both of the LEDs on the gateway flashing every 10-15 seconds)
• Verify that channel dipswitches inside the logger are set to the same position as the switches inside the gateway
• Cycle the power on the logger while it is in close proximity to the gateway and see if it will join the network
• If a logger will not join the Network after the previous suggestions have been tried, it may be out of sync with the gateway and needs to be reset
• To reset a logger, hold down the status button until the red and green LEDs turn on, then release (NOTE: Press and hold the status button on the logger ONLY, do not do this on the gateway)

Weak radio signal (red and green LEDs flashing), or loss of radio signal when moving logger to its final location:

• Try to improve the radio signal by:
  • Mounting the device as high as possible
  • Making sure there is plenty of clear space around the antenna
  • Removing obstructions from the radio path (clear line of sight is best)
  • Moving the logger to a better location (splice additional cable onto the instrument if necessary)
  • Adding more loggers to the network to provide alternate radio paths
• If the above suggestions do not correct the problem, a high-gain, directional antenna may be required: contact GEOKON for more information

Agent can’t connect to the Gateway:

• Cellular Gateways:
  • Ensure that the gateway is connected to an external power supply and that the power switch is set correctly
  • Verify the gateway is connected to the cellular network by pressing the status button and observing a green, or green and red flash on the LED indicators
  • Make sure the token entered into Agent software is correct, and that the correct “Cloud Network” has been chosen
• Local Gateways:
  • Ensure that the D batteries are properly installed
  • Replace batteries if they are depleted
  • Make sure the power switch is set to the correct battery type: lithium or alkaline
  • Make sure the USB or RS-232 cable is securely connected to the gateway and the PC
  • Make sure the address (COM port) entered into Agent software is correct

No Data from a Logger:

• Take a test reading by pressing the status button on the gateway (reading will be available for download within the next 6 minutes, depending on radio cycles and gateway type)
• If necessary, data can be retrieved directly from a logger by following these steps:
  1. Connect a PC to the USB port
  2. Create a new network in Agent software
  3. Enter the COM port the logger is connected to as the Network Address
  4. Download the data

Logger data is present (e.g., battery voltage or signal strength), but the Vibrating Wire or Thermistor Reading is Missing, Incorrect, or Unstable:

• Verify that the gauge leads are wired correctly (refer to the GeoNet instruction manual for wiring information)
• Multi-channel and addressable loggers stop trying to read empty channels after two attempts; additional attempts occur at the top of every hour (reset the logger to initiate an immediate retry)
• Move any sources of electrical noise away from the transducer cable (generators, motors, arc welding equipment, etc.)
• Check sensor operation with an independent readout, such as a GK-404 or GK-406

A USB driver is a file that allows GEOKON dataloggers, readouts, and other hardware devices to communicate with the operating system of a computer.

Installing USB drivers is an essential part of the setup process; if they are not installed correctly the device will not work.

USB drivers for GEOKON devices can be downloaded from www.geokon.com/software. If you have installed the USB drivers but they are not working, the drivers will need to be reinstalled as follows:

1. Right click on the CDM.zip folder and then select “Extract All…”
2. A new window will open. Select a location for the file and then click “Extract”.
3. Locate the extracted CDM file. Right click on the file and then select “Run as Administrator”.

If the USB drivers still don’t work after installing them in this manner, please contact your IT department.

• Download our Agent vs 3rd-Party Software Comparison sheet (pdf)›