PART 4 – Remote monitoring of tailings dams Q&A series: sensor and security queries

To round off our series of Q&As based on our webinar on IoT remote monitoring of tailings dams, Denis Guilhot and Juan Pérez Arcas are back to answer more of the queries that you posed in our webinar on IoT remote monitoring of tailings dams, which is now available on demand. This time round, our experts tackle questions on sensors and security.


Sensor-related topics

How is soil shear strength estimated at depth?

Juan Pérez, geotechnical engineer, wireless monitoring expert and product owner of the IoT-based monitoring system Loadsensing: 

I am not an expert, but as moisture has a significant effect on the soil shear strength an indirect measurement of the soil shear strength is to monitor the moisture. The relation between these parameters should be determined in the laboratory, considering in-situ conditions. It is possible to install soil moisture sensors at depth.

What will cause frequency data for the same piezometers to fluctuate significantly several times within a week?

Juan Pérez: 

I suppose the question is related to a vibrating wire piezometer. Probably the strength of the signal is not good enough and the measurement device is sometimes measuring the natural frequency of the wire and other times measuring noise. We are going to release new firmware for vibrating wire piezometer nodes, to reject readings if the strength of the signal is below a threshold. Meanwhile, I suggest checking the installation, cables, connections and the sensor. 

You can follow the troubleshooting suggested by vibrating wire piezometer sensor manufacturers for these cases.

Is it possible to read and connect flowmeters? What are the requirements?

Juan Pérez: 

It depends on the flowmeter and the application. For instance, it is possible to monitor the flow of water with a vibrating wire weir monitor and a V-notch. There are also some flowmeters with a pulse output compatible with the Loadsensing Piconode. Finally, there are flowmeters with Modbus RS485 output that could be integrated into  Loadsensing systems. Contact Worldsensing and we will try to provide a proper solution.

Are the data loggers also capable of reading TDR [time-domain reflectometry] sensors?  

Juan Pérez: 

We don’t have our own solution for TDRs. However, Geosinergia, our Chilean and Peruvian partner, has developed a solution on top of Loadsensing. It is possible to monitor the length of the cable measured with an integrated solution consisting of a Loadsensing node and a module developed by Geosinergia. Please contact us if you require any additional information about this solution.

Security and resilience

How fast can you send an alarm to warn a population in case of an earthquake or torrential rain events?

Denis Guilhot, innovation project manager for mining: 

It can be done instantaneously because we can automate that kind of process. The message can be sent by any means, from sending emails to radio broadcasts or phone or app messages. We can also use official national broadcasting systems. The important aspect is how long it takes to ensure the incident is detected in a failproof manner, so we can make sure we send the correct message. This can be done instantaneously as well, as long as we use the correct technology and the operator has defined the correct business rules.

If a sensor loses its connection with the gateway, does it store the data locally until connection is re-established… or is data lost?

Juan Pérez: 

Loadsensing nodes are also data loggers, so they can store up to 200,000 readings from a single sensor. If a node loses its connection with the gateway, it stores the data locally and can be manually collected with the app. In addition, the system detects the disconnection of the node and sends an alert email to fix the issue.

If you use automatic collection and the modem goes down, what happens to the data? Can the missing data be collected remotely once the modem is restored? 

Juan Pérez: 

As part of our embedded architecture, the gateway continues collecting readings. As soon as the gateway recovers connectivity all readings are available, and data is automatically pushed to the FTP client.

Are there security concerns with remote monitoring, including hacking or jamming signals?   

Denis Guilhot: 

As in all wireless networks, there is always a risk of hacking and/or jamming. In all our years in the industry, we have never suffered or heard complaints of hacking and jamming is not straightforward because of the wireless communication protocol we are using. Nevertheless, Worldsensing has been working on a jammer detector to protect installations. Our customers are usually more exposed to vandalism than hacking and jamming, so physical security measures are generally enough to protect the remote monitoring system.

How is data protected during transmission?

Juan Pérez: 

Data protection and privacy are achieved through 128 AES [Advanced Encryption Standard] encryption on multiple levels, for all data being sent from the sensors to the application server and back.

Doesn’t the fact that the instruments responsible for communication are located in the zones of influence themselves make them risky installations?

Juan Pérez: 

Loadsensing nodes are located close to the sensors. Optimal sensor locations should be based on the criteria related to zone types within the embankment and the rock bed. Usually, the installation of the sensors and the installation of the nodes is done in stable conditions. Installing nodes when a structure is likely to collapse is very rare, and in this case specific safety measures have to be considered.