New SDI-12 submersible hydrostatic level transmitters from Impress Sensors & Systems can be used in depths of up to 200m. The transmitter offers an SDI-12 digital output and an inbuilt high-accuracy temperature sensor.
The new SDI-12L transmitters have either a stainless steel silicon-based pressure sensor or a ceramic pressure sensor in marine-bronze. Both versions use piezoresistive technology, which provides long-term stability and repeatability.
According to Impress Sensors & Systems, the transmitters suit a wide range of applications, including:
- Monitoring river and reservoir levels
- Tanks and vessels in process plants
- Seawater and estuary levels
- Borehole water levels
- Tsunami and tidal monitoring systems
- Wave height measurement
- Environmental monitoring
- V-notch weir flow measurement
The stainless steel version offers a higher resolution of pressure measurement to around 12-13 bit and has a much lower signal-to-noise ratio, providing a very smooth and accurate method of level measurement.
On the other hand, the ceramic pressure sensor version is better suited to marine use, where stainless steel devices may suffer from corrosion.
SDI-12L transmitters are offered with measurement ranges from 0.5mWG up to 200mWG. The output units can easily be adjusted to mmWG, cmWG, inHg and all of the standard engineering units required via the SDI-12 interface and command structure. The temperature range is from -20 to +60degC. Accuracy of the inbuilt temperature sensor is less than +/-0.1 per cent of full-scale output.
Due to its SDI-12 compatibility, the transmitter can be corrected according to the specific density of the media being measured and local gravity can be set within the device, thereby improving the unit's accuracy still further.
SDI-12 stands for serial data interface at 1200 baud. This standard was developed in order to interface battery-powered data recorders to microprocessor-based sensors designed for environmental data acquisition (EDA).
EDA is accomplished by using sensors and a data recorder. SDI-12 is a standard communications protocol that provides a method of transferring measurements taken by a smart sensor to a data recorder. The sensor typically takes a measurement, performs calculations based on the raw sensor reading, then outputs the measured data in engineering units.
SDI-12 is particularly useful in applications where battery-powered operation with minimal current drain is required, or where the use of one data recorder with multiple sensors on a single cable is necessary. This includes acquiring hydrologic data at remote sites, where battery-powered data recorders operate unattended for long periods.
The SDI-12L is ideal for borehole pump applications. To operate efficiently, the pumps must maintain a level of water above them to prevent them running dry, which could damage the pump very quickly. In this type of application the SDI-12L can either be submersed with the borehole pump and attached to the bracketry or retrofitted by lowering the transmitter into the borehole to a known depth. The sensor will then output a signal to the surface via the cable, which can then be converted to a level reading. Using a digital process display, this signal can then be used to trigger a relay and turn the pump off if the water level is too low or switch the pump on if the level in the borehole has risen too high.
Follow the link for more information about SDI-12 submersible hydrostatic level transmitters from Impress Sensors & Systems.