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ADC Acoustic Digital Current Meter
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Overview

The OTT ADC (Portable Acoustic Digital Current Meter) is designed for point velocity measurements in natural streams, rivers, creeks and open channels. Using the latest acoustic measuring principles and combined with a high end signal processor the instrument provides accurate and reliable data.

The instrument is equipped with a built-in pressure sensor that provides automatic depth readings for the determination of both individual vertical depths and prompting the user to set the correct sensor position.

The instrument easily attaches to different types of wading rods and features an automatic discharge computation based on the internationally recognized ISO and USGS standards.

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Detailed Description

The OTT ADC is a mobile, acoustic current meter for measuring point velocities in open waterways. It is used for discharge measuring with the classic verticals process with conventional rods. During a discharge measurement, the OTT ADC measures not only the vertical velocity distribution at the verticals but also the water depth and the respective depth of the sensor. It calculates the average speed at the verticals from the measurements and also the partial flow in a flow segment. Finally, it calculates the sum of all partial flows to determine the complete discharge.

There are two ultrasonic transducers in the sensor head of the OTT ADC. While measuring the flow velocity, these transmit ultrasonic signals, which are reflected by the waterway particles and return as echo signals. The echo signals are received by the transducers and digitalized by a digital signal processor (DSP) as an echo pattern. After a short pause the process is repeated so that there is a second echo pattern. The DSP checks both echo patterns for similarity using a mathematical procedure and calculates their time difference. The difference is then used to calculate the flow velocity.

Specifications

Water Velocity Measurement

  • Range: -0.2 m/s to 2.5 m/s 
  • Accuracy: ± 1 % of the measured value ± 0.25 cm/s 
  • Resolution: 0.001 m/s 

Sampling Volume

  • Distance from sensor: 10 cm
  • Diameter: 1 cm per sound pulse 
  • Length: 5 cm 
  • Acoustic frequency ultrasonic transducer: 6 MHz 

Depth measurement

Piezoresistive pressure cell (absolute)

  • Range: 0 to 5 m 
  • Accuracy 0.1 % FS 
  • Resolution 0.01 % FS 
  • Max. overload: 1.5 times the measuring range 

Temperature measurement

  • Range: – 5 °C to 35 °C 
  • Accuracy: ± 0.5 °C 
  • Resolution: 0.1 °C 

  • Salinity Range: 0 ppt to 50 ppt (mg/l) 
  • Power supply Type: fixed battery pack, NiMH Nominal voltage 9.6 VDC. Life typically > 20 hours. Charging cycles > 500 
  • Output voltage of power supply: 16 VDC 

Operating conditions

  • Operating temperature range: – 20 °C to + 60 °C
  • Storage temperature range: – 40 °C to + 85 °C 
  • Shock resistance: compatible with EN 60068-2-32 

Dimensions & Weight

  • Cylindrical sensor body Ø 40 mm Length 14.5 cm 
  • Weight in air: 800 g 
  • Weight in water: 620 g 
  • Handheld unit Weight: 700 g 
  • Dimensions (L x W x H) 23.3 cm x 8.3 cm x 3.2 cm 

Material

  • Material Sensor housing: Delrin® / stainless steel 
  • Screws stainless steel 
  • Handheld unit: Aluminium, powder coated 
  • Keyboard Autotex V 150 XI IP protection class 

IP Protection Class

  • Handheld unit IP 65 housing, IP65 keyboard 
  • Sensor: IP 68 

EMC

  • EN 61000-6-2:2001 
  • EN 61000-6-4:2001 
  • FCC Part 15, subpart B, Section 145109 
  • EMC Directive 89/336/EEC, Article 4 
  • EMC Directive 2004/108/EU, Article 5 

Internal Data Memory

  • Capacity: 4 MB (flash) 

Ultrasonic Transducers

  • Frequency: 6 MHz 
  • Beam angle: 20° 

OTT QReview software

  • Operating system: Windows®98, Windows®ME, Windows®NT, Windows®2000, Windows®XP, Windows® Vista 
  • Functionality: Data transfer from handheld unit Data check and processing Data export (XML, ASCII)