Installing the Wind Vane
- Slide the wind vane down onto the shaft as far as it will go. (Because of the shape of the shaft, the vane will only go on one way.)
- Use the Allen wrench provided to tighten the set screw on the side of the wind vane.
- Test your assembly by pointing the wind vane in any direction and (using the compass or map as a guide) making sure the software status displays the correct wind direction. Readjust the cups if necessary. Note: For U30-NRC or Micro Stations, select Status in HOBOware® to get the current reading. For RX3000 Stations, use the RX3000 Manager in HOBOware to view the latest conditions. You can also check the latest reading in HOBOlink®, but the data is only updated when the station connects to HOBOlink. Refer to the software user’s guide or online help for details on operating HOBOware or HOBOlink.
Secure the Cables
To prevent fraying or cutting the anemometer cables where it is exposed to weather, secure it so it does not whip about in the wind. Use electrical tape or weather resistant cable ties to secure the cable. Place tape or cable ties approximately every 1 to 1.6 m (3 to 5 ft). Do not use metal staples to secure cables as they can cut the cables. Make sure there are drip loops on both sides of the smart sensor housing, which must also be mounted horizontally as described under Mounting Considerations.
Connecting the Sensor to a Station
To connect the sensor to a station, stop the station from logging and insert the smart sensor’s modular jack into an available smart sensor port on the station. See the station manual for details on operating stations with smart sensors.
Measurement Operation
Wind direction measurements are averaged over the logging interval or a 3-second timeframe (whichever is greater). If you set up the sensor to log faster than every 3 seconds, the same sensor reading will be recorded until a new 3-second average is calculated. For example, if the sensor is logging at a 1-second interval, the sensor will report the same wind direction (its calculated average) for three samples before calculating and reporting a new value for another three samples. Measurement averaging for this sensor is independent of the logger’s measurement averaging. Therefore the automatic measurement averaging for this sensor is not affected by any sampling intervals entered for averaging on other sensors.
Direction Averaging
Unit vector averaging is used to determine wind direction because traditional averaging would produce inaccurate results. For example, three measurements of 350, 11, and 12 degrees-which are all winds from the north-averaged together would result in 126 degrees, which incorrectly indicates a southeasterly wind. Instead, the vector components (North/South and East/West) for each wind measurement are calculated every three seconds for the duration of the logging interval. At the conclusion of the logging interval, the North/South and East/West components are averaged and then re-combined to calculate the average wind direction for the logging interval.
North Alignment
The sensor must be oriented to true north to obtain meaningful data. There are two methods to align the sensor:
- Compass Alignment
- Global Positioning Satellite (GPS) alignment
Compass Alignment
Tools required:
- Compass
- Binoculars
- Tape (such as electrical, packing, or duct tape)
Two people are required to complete this procedure.
- Position the wind vane so that it points in the same direction as the mounting arm. Secure the vane on the arm with a piece of tape so that the vane cannot rotate.
- While standing 150 to 200 feet south of the sensor, use the compass to determine magnetic north. If true north is the same as magnetic north, align yourself so the compass points north and directly at the sensor. If you are in area with an east variation, align yourself so that the station is that number of degrees to the east of magnetic north. If you are in an area with a west variation, align yourself so that the station is that number of degrees to the west of magnetic north.
- While viewing the sensor through binoculars, instruct another person to rotate the arm to point the vane north. The vane should seem to disappear from sight when properly aligned.
- Once you’ve obtained the correct position, secure the sensor base and remove the tape.
GPS Alignment
Tools required:
- Handheld GPS with WAAS-enabled receiver or any similar high accuracy GPS device
- Flag, orange cone, or other temporary marker
- Laptop computer with logger software installed
This procedure requires only one person, but is easier to complete with two people. In this procedure, you will be using the GPS receiver first to create an arbitrary waypoint and then to determine the bearing from the sensor to that waypoint. You will then align the sensor so that when the vane is pointed at the waypoint, the direction reported by the logger software matches the GPS receiver’s bearing to the waypoint.
- Connect the sensor to the station and connect the station to a laptop with HOBOware installed.
- Pick a visible location that is at least 100 meters (110 yards) away from the sensor and walk to it. Establish a waypoint with the handheld GPS receiver. You may want to use averaging to minimize the waypoint position error if your GPS receiver is so equipped. (For best results, the estimated position error of the waypoint should be less than 10 feet if the distance to the sensor is 100 meters, and less than 20 feet for a distance of 200 meters. Mark the waypoint with a flag, orange cone, or other suitable marker. Walk back to the sensor and determine the bearing to the waypoint you just created with the GPS receiver. Again you may need to determine the average value of the bearing to keep the errors to a minimum.
- View the current sensor readings in the software while positioning the arm. For U30-NRC or Micro Stations, select Status in HOBOware to get the current reading. For RX3000 Stations, use the RX3000 Manager in HOBOware to view the latest conditions. You can also check the latest reading in HOBOlink, but the data is only updated when the station connects to HOBOlink. Refer to the software user’s guide or online help for details on operating HOBOware or HOBOlink.
- Point the sensor vane directly at the waypoint flag or marker and rotate the sensor mounting arm until the wind direction sensor value in the logger software matches the angle obtained with the GPS receiver.
- Once the vane is in position, secure the mounting base and then double-check that the reported angle is correct.
Maintenance
The sensor does not normally require any maintenance other than an occasional cleaning. If the vane becomes dirty, rinse it with mild soap and fresh water. Do not immerse the sensor in water or use any organic solvents to clean the unit. Do not attempt to lubricate the wind cup shaft or bearings or the wind vane shaft. Natural or synthetic lubricants will inhibit the normal operation of the anemometer.
Verifying Sensor Accuracy
It is recommended that you check the accuracy of the sensor annually. The sensor cannot be calibrated. If the smart sensor is not providing accurate data, then it is damaged or possibly worn out if it has been in use for several years.