OTT Hydromet launches self-draining rain sensor

Kempten, Bavaria ( press.abc-directory.com ) September 10, 2018 - The OTT Hydromet Group is one of the leading providers of hydro logical and meteorological sensors. These include various measuring systems for the detection of liquid and solid precipitation. These can be used in both cold and warm climate zones. Recently, the precipitation sensor family has been joined by two new models: The maintenance-free, radar-based Lufft WS100 in 2017 and the OTT WAD in 2018. WAD stands for "weighing and draining" and describes a unique measuring principle that combines the advantages of weighing and collecting rain gauges.

The high measuring accuracy meets the requirements of WMO guideline No. 8. It specifies that rain sensors have a maximum inaccuracy of ± 3%. In addition, it outputs precipitation intensities and total values in real time in the impressive measuring range of 0.001 to 720 mm / h.

The new, self-draining tilt-balance system represents an alternative to the OTT Pluvio² sensor and is especially suitable for use in subtropical and tropical climates. These are characterized by heavy rain showers with up to 10,000 mm per year as well as extreme weather events in the form of hurricanes and typhoons. It is able to output the measured values "event" (rain yes / no), rainfall, rain intensity and the total amount.

The OTT WAD combines a tilting and a weighing system. This has the advantage that the sensor takes into account weight increases and does not distort data by evaporation or unintentional emptying, as it can be the case with collection bucket.

The priciple explained in more detail

The high-precision, monolithic, self-draining collection device has two chambers that alternately fill with precipitation. When a certain volume is reached, the monolith tilts and empties. Each droplet is monitored at a resolution of 0.001 mm / m², accurate to ± 10 mg due to the high-precision weighing system.

Calibration

Calibration is performed using a precision reference weight in combination with monitoring, configuration, and maintenance software. The sensor is connected to the computer via a standard USB port. The calibration and adjustment are possible according to the ISO standard over the entire intensity range from impressive 0 to 720 mm / h.

Interfaces

The OTT WAD precipitation sensor combines maximum functionality with a very compact design. A total of six analog, digital and serial interfaces, such as SDI-12 and RS-485 with different output telegrams, allow easy integration into different systems and networks.

Testing

In field tests, in which meteorological services and institutes compared the OTT WAD directly with collecting weighing sensors or manual testing gauges, no negative measuring effect could be detected by the funnel. It is the successor to conventional tilting bucket systems, which are particularly suited to the comparison of long time series and historical precipitation data and based on the same housing design and two-part tilting bucket system. However, the primary weighing principle of the new WAD ensures far better measurement performance than its predecessors.

Measurements and weight

The small housing dimensions and the low weight of 2.5 kg result in lower logistics and installation costs than other weighing systems or optical precipitation sensors. The OTT WAD is thus approximately 50% cheaper than other precipitation gauges - with comparable or even superior functionality. It is, therefore, suitable for integration into existing measuring fields and in hard-to-reach places and can easily replace tilting scales or manual measuring devices.