AANDERAA INSTRUMENTS DATA COLLECTING INSTRUMENTS FOR LAND SEA AND AIR WATER LEVEL/TEMPERATURE SENSOR, WLTS. Series 3791 - 3798 These sensors, based on measuring the hydrostatic pressure and water temperature in a fixed submerged position, are designed to be used with Aanderaa Dataloggers and Display Units. The Water Level Sensor consists of: • Pressure Sensor with Thermistor • Cable with Airpipe • Compensating Unit The sensors can also be delivered as averaging versions which is given suffix A in the part number. These versions will minimize the influence of ripples or waves on the measurements. is a sensor with low ageing, small hysteresis and great resistance to mechanical shocks and vibrations. The output from this sensor is in the VR22 Aanderaa standard. The sensor has a thermistor measuring the water temperature and the output is also VR22. Accurate monitoring of tide and the water level in ports, coastal and inland waters, rivers and boreholes is of great importance to many practical projects. This series of water level or tide monitoring sensor measures the hydrostatic pressure caused by the head of water above them. The influence of barometric pressure on the sensors is compensated for by applying air pressure to one side of the transducer through an air pipe and compensating unit. The sensors contain, in addition to the sensing element, a temperature compensating and a range reducing network. The averaging versions is designed to monitor water level or tide where waves and ripples may disturb the measurements. In this version the signal from the sensing element is sampled every second and a microcontroller calculates the average value at the end of each measuring cycle. This continuous averaging of the pressure reduces the fluctuations caused by ripples and waves. The current consumption is 1.0 mA continuously and the output is the SR10 Aanderaa standard. The entire electronic circuit is mounted on a board inside the Pressure Sensor and molded into Scotchcast. Other parts exposed to water are made of titanium and this forms a compact and rugged sensor with no corrosion problems. The sampling interval between measurements is controlled by the data logging system and can be set in fixed steps from 1 minute up to 3 hours. The sensing element of these units, a small silicon chip with a thin membrane at the centre, is subjected to atmospheric pressure on the one side and water pressure on the other. Four diffused resistors on the chip, in the form of a Wheatstone bridge, give an output signal proportional to the differential pressure. The consequence of using monolithic technology DATA SHEET D 325, SEPTEMBER 2000 The sensors tolerates operating submerged in purified kerosene.

SPECIFICATIONS Two versions are available; The Momentary Version 3791-98 and the Average Since Last Version 3791A-3798A Pressure: Titanium sensor body Pt-element Standard Ranges: Accuracy: Resolution: Temperature: Range: Accuracy: Resolution: Response time: Electrical Connection: Electronic board Current Consumption: Momentary version: Average version: 1.0 mA when monitoring 1.0 mA continuous -2 to + 40°C Scotchcast and titanium IP 68 Net weight 2.6 kg; Gross 3 kg Cardboard box,390x230x250mm Two years standard against faulty materials and workmanship Note! Our standard warranty (2 years) is not...

CALIBRATION Temperature: Pressure Sensor Type: Range 0 – The sensor is connected to a Datalogger 3660 and calibrated against a Budenberg 240 dead weight tester. The following pressures gave the readings N: To refer the water level to a Chart Datum: As tides are reported as surface fluctuations relative to the local Chart Datum it is necessary during the establishment of the tide gauge, to install the sensor at the lowest predicted water elevation. To refer the water level to a specific reference level or Chart Datum a correction factor must be found. These readings give a set of coefficients...

APPLICATIONS Water Level and Meteorological measurements are often used in combination. Below is a simple system monitoring the most common meteorological parameters at for example in ports or water reservoirs. Data can be stored at site or transmitted in realtime to the user’s location either via VHF or UHF radio. VHF/UHF Receiver Computing Unit 3015 Data stored on site in DSU 2990 and/or transmitted via radio to a receiving station Datalogger 3660 DATA LOGGER 3660 SERIAL NO: AANDERAA INSTRUMENTS Data from Field Stations Terminal Program PROGRAMMING: - Turn the Mode Switch to Menu pos. - Press...