Better defense against climatic anomalies using dependable level sensors

Better defense against climatic anomalies using dependable level sensors

Over the past few years, Russia has been increasingly struggling with environmental disasters caused by extreme weather conditions. This has not only led to massive material damage, but has also cost human lives. An extensive structural program for better weather forecasting is now destined to diminish those risks and also to support research on climate change.

Weather anomalies, such as the extensive drought of 2010 or the heavy flooding in the Amur region in 2013, generated major attention and concern within Russia, as well as beyond. The Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet) is responsible for high-precision weather forecasts in Russia and is now to be further bolstered under the terms of the Hydrometeorological Services Modernization Project-II. A little over 139 million dollars has been invested for this purpose.

This large-scale modernization project will be supporting Roshydromet in providing the Russian population, as well as municipal authorities, with reliable and up-to-date information on weather, hydrology and climate. At the same time, Russia is also to be better integrated into the global system of meteorological services.

The individual project measures include:

  • Strengthening of information and communication technologies for providing data on weather, climate and hydrology,
  • Modernization of the observation network,
  • Consolidation of institutions,
  • Optimized access to Roshydromet data and information,
  • The improvement of disaster protection.

With the modernization of Roshydromet’s hydrological observation network in the Lena, Jana, Indigirka, Vilui and Kolyma rivers, special attention has been paid to monitoring technology, which, largely maintenance-free, performs reliably in difficult to access areas and also under harsh conditions such as permafrost.

Fig. 1: Overview of the monitoring sites

Some of the water level sensors essential here were provided by STS and, in collaboration with the Russian partner company Poltraf CIS Co. Ltd., installed at 40 hydrological monitoring stations. The project itself comprised the following requirements:

  • The permanent monitoring of water levels and temperatures, as well as the measurement of rainfall and snowfall. This also includes the installation of surveillance cameras to keep the formation of ice at strategically important points in view.
  • The automatic and error-free transmission of data via GPS or satellite.
  • An alarm function when exceeding defined limits.
  • A server solution for storing the collected data, including a software for the visualization, evaluation and processing of that data.
  • A simple-to-install and easy-to-use technology that will perform for years on end without major maintenance.
  • A professional preparation of the actual monitoring locations.

To meet this demanding assignment, the DTM.OCS.S/N/RS485 Modbus sensor, including others, has been employed. These digital level probes actually measure both level and temperature. The harsh conditions are addressed by its robust design and permissible ambient temperatures of -40 to 80 degrees Celsius, whilst an accuracy of ≤ 0.03% FS ensures precise results at critical measuring points.

Some further advantages of this digital level sensor in brief:

  • High-precision digital level sensor for easy integration into standard Modbus networks
  • Individual adaptation to application through modular design
  • Highest precision over the entire temperature range due to electronic compensation
  • Adjustment of zero offset and measurement range via Modbus
  • Extended long-term stability of measuring cell
  • Sensor can be recalibrated
Hydrostatic pressure measurement with piezoresistive level sensors

Hydrostatic pressure measurement with piezoresistive level sensors

Whether as a life-giver, a danger to life or simply a refreshment in summertime, the element of water determines daily life on earth in many ways. Because of its sheer importance, a reliable monitoring of this element becomes essential.

What cannot be measured can also not be managed efficiently. From fresh water supply, drinking water treatment, storage and consumption measurement, to waste water treatment and hydrometry, it will not be possible to work and plan efficiently without the correct input parameters. A range of devices and processes are now available to capture today’s complex hydrometric infrastructure. The classic in water level measurement is without doubt the level gauge, for which an accuracy of +/- 1 cm must be applied and which, of course, still functions completely “analog” – having to be inspected visually and doing without electronic data transmission. Today, far more advanced and precise instruments provide remote transmission of the measured data, including piezoresistive pressure sensors for water level measurement in both groundwater and surface waters.

Level measurement with pressure sensors

Pressure sensors for level measurement are installed at the bottom of the water body to be monitored. In contrast to level gauges, it is generally not possible to read them without getting wet. This is not necessary either, since piezoresistive level sensors were developed to meet today’s requirements for process automation and control. It goes without saying that water levels can thus be measured without human intervention, which makes continuous monitoring at difficult-to-access locations possible in the first place.

Hydrostatic level sensors measure the hydrostatic pressure at the bottom of the water body, where the hydrostatic pressure remains proportional to the height of the liquid column. Additionally, it is dependent upon the density of the liquid and gravitational force. According to Pascal’s law, this results in the following calculation formula:

p(h) = ρ * g * h + p0

p(h) = hydrostatic pressure
ρ = density of the liquid
g = gravitational force
h = height of the liquid column

Important considerations for trouble-free level monitoring

Because piezoresistive level sensors are placed at the bottom of the water body, they are then protected from surface influences. Neither foam nor flotsam can now influence the measurements. But, of course, they do have to be adapted to the expected underwater conditions. For salt water, for example, a level sensor with a titanium housing is to be preferred. Should galvanic effects be expected, however, then a measuring device of PVDF would be the best choice. In most freshwaters, high-quality stainless steel will be sufficient. And lastly, a sufficient grounding of the level sensors is essential to prevent damage from lightning strikes, for example (read more on this topic here).

Modern level sensors: All data from just one device

Piezoresistive level sensors can be used for level monitoring in open waters such as lakes, in groundwater occurrences and also in closed tanks. In open waters, relative pressure sensors will be used. With these devices, air pressure compensation is provided by a capillary inside the pressure sensor cable. A differential pressure sensor is normally used in tanks, since the gas overlay pressing down on the liquid must also be taken into account (read more on this topic here).

Because piezoresistive level sensors are largely self-sufficient and can also be optimized for very high pressures, measurements at great depths now become a possibility. Theoretically, there are hardly any limits to this depth, only that the pressure sensor cable has to be long enough.

Figure 1: Examples of level sensors for hydrostatic pressure measurement

Apart from the fact that there are hardly any depth limits, these modern measuring instruments are also extremely versatile. After all, it is not only the level of a water body that is of interest to us. Water quality is also of great importance for groundwater monitoring. The purity of a groundwater reservoir, for example, can also be determined by its conductivity, where the lower the conductivity, the purer the water will be (read more about conductivity here). In addition to conductivity sensors, level probes today are now also available with integrated temperature measurement. Piezoresistive level sensors provide a wide range of monitoring tasks and are without question preferable to the level gauge in most cases.