Landslides are a potenzial hazard and in particular situations it is absolutely necessary to keep them under control. The case we’re describing here is about the monitoring of the land adjacent to a newly bought highway. This work – recently carried out in a European Country – crosses a land with high risk of landslides. For this reason, it was installed a whole series of geotechnical instrumentation – piezometers, inclinometers and extensometers – able to monitor the land state. However, as it is known, landslides are often closely related to meteorological phenomena, that means substantially to the quantity of rain. Long periods of rain, especially in winter time, may be the trigger of a landslide in the following months. Sporadic rains, even if heavy, are usually less dangerous from this point of view. Therefore, it is necessay to acquire metereological data for enough long times.
The request is the creation of a meteorological data acquisition system to be associated with geothecnical measurements, in order to make a constant and as close as possible analysis of landslides risk. A data logger for geotechnical measurements is already used in the plant under construction. The possibility of expanding its inputs thus creating a system based on a single datalogger has been proposed, however the customer decides to have a dedicated system.
The primary purpose of the device will be to perform measurements related to the amount of rain, but since the application relates to a highway, the customer considers it appropriate to provide a complete weather station to measure environmental temperature and humidity and wind speed.
Other requirements; possibility of remote enquiry and alarms generation, IP 66 protection class and overall robustness suitable for this kind of use.
Next Industries manufactures – together with the data logger line NI2400 – also NI200/400 devices, which appears the ideal solution for this application. It is a last generation data logger, with moderate dimensions, designed for outdoor use, with a rugged IP67 case. There are 4 input channels, which are configurable as voltage input or current loop. All the inside electronics is subjected to tropicalisation: this increases electrical insulation, resistance to moisture and oxidation, in other words the long-term reliability. The reliability is further improved by the presence of gas dischargers and relay inputs. Although equipped with a powerful ARM CPU and 24-bit data acquisition, this data logger is able – if required – to work for long periods with the internal AA batteries. Data storage capacities fit for all needs; measures are in fact placed in a 2GB non-voltile memory. It is also possible to download them in a normal USB key. Another requested feature, meaning the automatic sending of notifications, has been made possible by a GSM modem built on a small plug-in module on the data logger main board. Through the same GSM modem, the data logger can send alerts based on user-defined parameters, both via SMS and e-mail. The following sensors have been used for this application; N.1 rain gauge N.1 anemometer N.1 temperature and humidity sensor
Next Industries does not have a rain gauge in its catalogue at the moment, so this has been found among devices on the market. The selected device is provided with a 4-20mA current loop output, and has been connected to channel 1 of the data logger.
Temperature and humidity sensor
Temperature and relative humidity sensor NI-EE60 is provided with 2 voltage outputs – for temperature and humidity respectively – which have been connected to channels 2 and 3 of the data logger. It was used together with accessories for outdoor mounting (solar radiation and rain protections).
NI-WSS-01 anemometer is a device provided with voltage output and has been connected to channel 4 of the data logger. An important feature of NI200/400 data logger is that it is able to perform an automatic conversion of the acquired measures into engineering units, like for instance transformation of the voltage value 0,4..2V output of the anemometer into meters/sec. wind speed and perform the data log of this last one.
CSV data transfer
In this kind of application customers usually want to monitor data and analyze them with their own software.
Through an FTP connection and with the internal modem NI200/400 is able to send data in CSV format to a server; this can happen after every acquisition or according to a preset time.
The meteorological data acquisition equipment perfectly integrates with the monitoring geotechnical plant, thus realizing a complete system able to provide the best analysis of the landslides risk state with high datalogging and remote interaction capacities which are provided by state-of-the-art technologies. More pieces of information about weather conditions are then available to the highway manager authority.