Direct Reading Electromagnetic Current Meters

Direct Reading ElectromagneticCurrent MetersModel 802FEATURESAPPLICATIONSINTRODUCTION■■■■■■■■■High AccuracyHigh StabilityLow NoiseLow Power ConsumptionChoice of Sensor ShapesChoice of ConfigurationsDigital or Analogue OutputWide Measurement RangeCorrosion resistant materials■■■■■■Sediment Transport StudiesHydraulic ModellingOpen Channel Current MeasurementShip’s LogROV/AUV SpeedFixed Site Current MeasurementThe Model 802 is the latest version ofValeport’s successful 800 Series ofelectromagnetic current meters. Usingstate of the art electronics designtechniques, we have produced a highlyaccurate, stable, solid state instrument thatis greatly reduced in size and powerconsumption from earlier versions. Theseimprovements, together with a selection ofsensor shapes and a versatile range ofelectronics packages ensure that the Model802 is the instrument of choice in a varietyof applications, from sediment transportstudies to modelling flow patterns or realtime monitoring of current flow.Output from the Model 802 is strictly inthe format of X and Y velocity componentsonly. If a compass or other additionalparameters are required, please refer to theModel 808 data sheet.

Direct Reading ElectromagneticCurrent MetersModel 802DESCRIPTIONElectromagnetic Current Meters work onFaraday’s principle that a conductor (water inthis case) moving through a magnetic field(produced by the sensor) generates a voltage(measured by a pair of electrodes). By having2 orthogonally positioned electrodes, 2 axisflow can be measured by a single sensor.Each Model 802 system comprises a sensinghead, and a set of electronics to produce themagnetic field and measure the resultantvoltage. Valeport offers a range of differentsensing heads and electronics assemblies tosuit different applications. Any of the listedsensors may be fitted to any of the electronicspackages to provide a Model 802 system. Thestandard output of all systems is RS232 of Xand Y components of the flow speed, relativeto the mounting position of the head.2 channel analogue outputs are also availableas an option.HeadsAnnular Sensor: The 17cm annular sensormeasures flow in the open space inside thering, and therefore has excellent response tooff axis flow. It is therefore most suitable foruse in applications where off axis flow isexpected, or for use in pairs to measure 3dimensional changes.Spherical Sensor: Available in either 3.2cm or5.5cm sizes, the spherical sensors havereasonable response to tilt and azimuth flowvariations, but are hydrodynamically noisierthan the other sensors. Spatial resolutionrequirements determine the choice of sensorsize.Discus Sensor: The discus sensor is availablein 3 sizes; 3.2cm, 5.5cm and 11cm diameter.Since the flow is measured on one face of thediscus, tilt response is as good as the othersensors ,but azimuth response is excellent,with low hydrodynamic noise. These sensorsare therefore suited to any applications wheretwo dimensional flow is expected. Again,choice of sensor size depends on spatialresolution required.ElectronicsControl Display Unit: This package consists ofan IP67 (10secs at 0.3m) display unit, and 3msignal cable to the sensor of choice. Thedisplay has an integral battery compartmentmaking it ideal for field use, or can bepowered using external DC for laboratoryapplications. Features of the display includereal time and averaged X & Y velocities andStandard Deviation of X & Y velocities. Theuser may choose the type of sampling required– fixed time, moving average, or free running,and the length of the average. In addition, thecontrol unit has an optional internal memory,which can hold up to 999 records of the aboveinformation, together with date and timestamp. Recorded data can be viewed onscreen or downloaded to PC in ASCII textformat.Integral Underwater Housing: Drivingelectronics and preamplifiers are contained ina stainless steel underwater housing, with thechosen sensor mounted on a stem protrudingfrom one end. A single connector allowspower in (12 to 24vDC) and RS232 signal outat 1Hz update rate. Output signal is in theformat X=sn.nnn Y=sn.nnn, where sindicates the flow direction + or -, and n.nnnsignifies the flow speed in m/s. 0-5v analogueoutput option is available for X & Y channelsRemote Underwater Housing: Exactly asIntegral Underwater System, but flow sensor issupplied on a 3m length of signal cable, ratherthan attached to the electronics housing.OEM Package: Driving electronics aresupplied as OEM parts, for interface tocustomers’ existing systems. Electronicsrequire power in (12 to 24vDC) and giveRS232 digital signal out. Sensor is supplied on3m signal cable, with free end. Again,analogue output is available as an option.SensorCharacteristicsAccuracy Depth Rating Tilt Response Azimuth Response Hydrodynamic Noise17cm Annular ±1% + 5mm/s 1000m ✓✓✓✓✓ ✓✓✓✓ ✓✓✓✓11cm Discus ±1% + 5mm/s 5000m ✓✓✓ ✓✓✓✓✓ ✓✓✓✓✓5.5cm Discus ±1% + 5mm/s 3000m ✓✓✓ ✓✓✓✓✓ ✓✓✓✓✓3.2cm Discus ±1% + 5mm/s 3000m ✓✓✓ ✓✓✓✓✓ ✓✓✓✓✓5.5cm Spherical ±1% + 5mm/s 3000m ✓✓✓✓ ✓✓✓ ✓✓✓3.2cm Spherical ±1% + 5mm/s 3000m ✓✓✓✓ ✓✓✓ ✓✓✓PackageSpecification (may vary slightly according to sensor selection)Size Power Consumption Depth RatingSensor on spar with pre-amp housing and 3m cableto Control Display UnitCDU: 250 x 170 x 100mm 240mA IP67 (10s at 0.3m)Underwater housing with integral sensor on spar,and 3m power in/signal out cable525mm long x 76mm∅ (inc sensor) 130mA 3000mUnderwater housing with remote sensor onspar/pre-amp housing, 3m sensor cable, and 3m 350mm long x 76mm∅ 130mA 3000mpower in/signal out cableSensor on spar with pre-amp, 3m sensor cable toOEM board set with wiring loom.54mm x 205mm 130mA N/AAlso Available2 channel 0-5v analogue output option for anypackage.ORDERING AND SPECIFICATIONSExtra Sensor cable (maximum 50m)Extra Power in/Signal out cable (maximum 100m)Alternative Signal ranges (standard ±5m/s for each axis)For more detailed specification, please referto additional sheet.Valeport manufactures a wide range ofoceanographic and hydrometricinstruments including self-recording anddirect reading multi-parameter currentmeters, CTD probes, electromagneticcurrent meters, tide gauges, open channelflow meters, optical instruments, waterand plankton samplers, winches, sinkerweights, connectors and accessories.As part of our policy of continuing development, we reserve the right to alter, without notice, all specifications,designs, prices and conditions of supply of all equipment. Data Sheet Reference No. 802/1Valeport LimitedTownstal Industrial EstateDartmouth, Devon TQ6 9LXUnited KingdomTel: +44 (0)1803 834031Fax: +44 (0)1803 834320e-mail: sales@valeport.co.ukWeb Site: http://www.valeport.co.uk