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Velocity/Discharge Sensors FAQ
ADC – Acoustic Digital Current Meter
Q: What is the minimum water depth for field deployment? A: 4 cm.
Q: Is it possible to delete data on the handheld using the QReview software? A: No.
Q: Is it possible to pre-configure measuring points/sites in the office? A: No.
Q: How often does the OTT ADC have to be recalibrated? A: No recalibration necessary.
Q: What are the main differences / advantages of ADC compared to a mechanical current meter? A: • No calibration needed.
Q: What maintenance is necessary? A: Sensor cleaning after deployment.
OTT Qliner– Acoustic Doppler Current Profiler
Q: What is the minimum depth required for measuring discharge with an OTT Qliner? A: The OTT Qliner can be used for discharge measurements in rivers, streams and open canals with a minimum depth of 1.2 ft (0.35 m) if using a 2 MHz unit and 1.5 ft (0.45 m) if using a 1 MHz unit.
Q: What is the average battery life of the Qliner? A: 12 or more hours
Q: What is the minimum battery voltage of the Qliner? A: Greater than 10.5 V, if less than 10.5 V connection via Bluetooth may not be possible.
Q: How many times can the battery be charged before it requires replacement? A: Several hundred times
Q: What is the typical life of the 9 volt battery in the Bluetooth adapter? A: 3 hours
Q: Does the OTT Qliner operate using the “bottom tracking” functionality? A: The OTT Qliner measures discharge using the section by section method, which does not require “Bottom tracking”.
Q: What is the purpose of beam 3? A: Beam 3 is the forward pointed beam tilted downward 20°. It measures the velocity close to the water surface. So it is possible to record data where beam 1 and 2 have limited capabilities. Beam 3 measurements are one dimensional.
Q: How the discharge is computed by OTT Qliner? A: The OTT Qliner supports the mid-section discharge method, ISO 748.
Q: What is the recommended measuring time? A: The minimum measuring interval is 30 seconds. For sites with moderate to moderately high velocities a 30 to 45 second measuring interval is ideal. If measuring slow velocities, extending the measuring interval will increase the accuracy of the measurement.
Q: What is the recommended cell size? A: The recommended cell size is in the range of 0.3 to 1 ft (10 to 30 cm). A larger cell size decreases the standard deviation of the measured cell velocity.
Q: What is the recommended number of cells? A: The recommended maximum number of cells is 40. It is possible to setup as many as 128 cells; however, the processing time is greatly increased. The number of cells is calculated automatically when you change the cell size or maximum depth.
Q: Can I change cell size during a discharge measurement? A: Yes the cell size can be changed during a discharge measurement.
Q: What is the relationship between standard deviation in cm/s of measured cells, measuring time and cell size? A: See table below.
Q: How do I fix the rope to the boat while measuring from a bridge? A: When deploying the OTT Qliner from a bridge attach the two strands on the front of the boat as seen in the figure below.
Q: How can I reduce the drift of the boat at high velocities? A: Depending on the current and the height of the bridge it may be necessary to add an extra weight to the rope in order to reduce the drift of the boat.
Q: What is the maximum river width for OTT Qliner measurements? A: The maximum river width depends on your vertical and horizontal position relative the boat. The Bluetooth adapter on the PDA can communicate with the Bluetooth adapter in the boat as far as 230 vertical and 650 horizontal feet away providing a direct line of sight.
Q: The computed discharge on the PDA differs from the result in Qreview. What is the reason? A: The “use beam 3” box under General Setting was not selected during the initial setup of the discharge measurement but in Qreview it is was selected under settings in QReview. Deselect the checkbox for “use beam 3” in the “Settings” drop down menu of Qreview and compare your results again.
Q: What could be happen if I have problems with Bluetooth data transmission? A: If your Bluetooth connection fails, first check the power supply (9 V block battery) of the Bluetooth transceiver connected to the PDA. Change the battery if necessary. Check also the alignment of the Bluetooth antenna which is attached to the PDA. It should be aligned parallel to the antenna inside the boat.
Q: My PDA is equipped with Bluetooth. Can I use it for OTT Qliner operation? A: OTT Qliner is equipped with Bluetooth Class 1. The Bluetooth transceiver set is configured as a “serial cable replacement”. This means that both transceivers were configured to act as a ‘one to one’ cable. It is not possible to connect the OTT Qliner using any other Bluetooth device or PDA with Bluetooth capability.
Q: Does the OTT Qliner give information about the velocity at different depths? Or only an average value for each vertical? A: The OTT Qliner provides velocity information for each measured cell as well as the mean velocity for each vertical. Average velocity and graphical representation of individual cell velocity is displayed on the PDA after each measurement vertical and in QReview. The displayed cell velocities refer to the mid point of the cell.
Q: What is the ping rate of the OTT Qliner? A: The ultrasonic sensors emit 3 pings per second and a 3 second average is displayed real-time using the Qliner PDA software.
Q: Do I need to keep the boat normal to the cross section? A: The boat should be aligned perpendicular to the cross section. A 10°misalignment could result in a 1.5% measurement error. To avoid alignment errors enable the compass correction.
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