Model 6527A Starflow QSD Ultrasonic Doppler Velocity and Depth SDI-12 Instrument
The Unidata 6527 Starflow QSD SDI-12 Instrument is used to measure water velocity, depth and temperature of water flowing in rivers, streams, open channels and large pipes.
When used with a companion Unidata IP data logger, flow rate and total flow can also be calculated.
6527 Starflow QSD SDI-12 Instrument is robust, reliable and easy to use. It is completely sealed against water ingress, low maintenance – no calibration, low power – no fussy power arrangements needed.
Ultrasonic Doppler Principle in Quadrature Sampling Mode is utilised to measure water velocity. 6527 transmits ultrasonic energy through its epoxy casing into the water. Suspended sediment particles, or small gas bubbles in the water reflect some of the transmitted ultrasonic energy back to 6527 instrument’s ultrasonic receiver. instrument than processes this received signal and calculates the water velocity.
Water depth is also measured with an ultrasonic depth sensor. This technology enables the Starflow QSD SDI-12 Instrument to be completely sealed; potted in a solid block of ‘ultrasonic-transparent’ epoxy and free from any potential leaks that might otherwise occur.
Using an ultrasonic depth sensor also avoids the vulnerability of conventional pressure sensors to damage from water-borne debris and avoids the need for frequent recalibration to maintain accuracy.
6527 instrument is suitable for use in a wide range of water qualities, from sewage to potable water including sea water. However, it may not be as effective in clean, gas-free water.
6527 instrument measures velocity in both directions. With a companion Unidata Starlog datalogger or Neon Remote Terminal the instrument can be programmed to compute flow rate and total flow in pipes and open channels of known dimensions.
Simply mount it on, or near the bottom of the water channel. Starflow QSD SDI 12 Instrument’s low-profile form-factor minimises disturbance to the flow it’s measuring.
Material: Epoxy-sealed body, Marine Grade 316 Stainless Steel Mounting Bracket
Size: 135mm x 50mm x 20mm (LxWxH)
Weight: 1kg with 15m of Cable
Operating temperature: 0°C to 60°C water temperature
– 20mm/s to 1600mm/s in one direction
– 20mm/s to 3200mm/s in one direction (parameter setting)
– Bidirectional flow capacity (parameter setting)
Velocity Accuracy: ±2% of measured velocity
Velocity Resolution: 1mm/s
Depth Range: 20mm to 2.0m/5.0m*
* Range is above sensor and up to 2000mm in water with heavy sediment and up to 5000mm in water with medium sediment.
Depth Accuracy: Typical ± 1%
Temperature: 0°C to 60°C
Temperature Resolution: 0.1°C
Flow Computation: Flow rate, totalised flow
Channel type: Pipe, open channel, natural stream
Cable: 15 metre, 3 way
Cable Options: User specified up to 50 metres
Power Source Typical: External Battery 12V DC
Power Usage: 10V to 24V DC, 50µA standby, 100mA active for 1 sec
SDI-12: SDI-12V 1.3 recorder (1200 baud smart instrument channel)
Full product consists includes mounting bracket
|6527A||Starflow QSD SDI-12 Instrument|
|6527A-S||Special cable length (up to 50m) Starflow QSD SDI-12 Instrument|
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A: The QSD has a half power beam width of 2.8 deg which means the transmitter & receiver beams begin to intersect about 100mm from the face of the instrument. However this is the half power width; lower power intersection occurs closer than 100mm and given the receiver sensitivity will contribute to the velocity detection. Suspended particles reflect the signal at many angles, so even before the beams intersect there will be high angle Doppler reflections that are received.
Also, the beams will be internally reflected off a shallow water surface and mix further “upstream” so it is difficult to determine where the maximum signal is coming from and even more difficult to say if there is a dead band and how large it is.
Hence, the zone of maximum sensitivity lies from 100mm to 300mm from the instrument but it depends on water level (reflection) and quality (number of reflectors). Instrument will detect velocities from 25mm onwards.
Q: Can the Starflow QSD be used in small pipes
A: We have been testing the operation of QSD’s in a 150mm pipe for some months now.
The performance of QSD’s in this arrangement is good. Just watch for turbulence and if you plan to use a dam, watch for standing waves.
We have a small pipes test tank here at Unidata. It consists of a 150mm PVC pipe and submersible pump etc.
We have been running these QSD’s down to a depth of about 60mm in this arrangement with no real problem.
Q: What is the angle of the ultrasonic beam when using Starflow QSD to measure water level?
A: Beam Width is 3.5° (-3dB point)
Q: What is the angle of acoustic beam with or spread when using Starflow QSD to measure the flow rate?
What is the angle of the centreline of acoustic beam?
A: The acoustic beam has a width, or spread, of about 10°. The centreline of the beam is aligned at 30° above horizontal but as a particles passes horizontally through, the actual angle within the beam varies from 25° to 35°
Q: Will water level measurements be affected if ultrasonic touches the wall of the pipe?
A: The Starflow QSD should not be affected by the depth signal reflecting of the tube wall. This will cause a “smudging” of the return signal, but Starflow QSD detects first pulse and ignores subsequent returns due to multi-path reflection.
Q: The Starflow QSD is used in the water channel. The water level and flow rates can suddenly change.
What is response time to depth change?
A: Response time to depth change is controlled by the amount of the filtering/averaging being used. If no averaging is used, the depth measurement will be immediate depth value at the time of measurement. The response time is then determined by the rate of SDI-12 interrogation.
Averaging is used in open water conditions to smooth out the effect of surface ripples/waves.