Wind Speed

(i) Range of Application - The combined wind sensor is designed to record wind

values and to convert these values into electrical signals. The signals can be fed into a combined indicator which presents the wind velocity in a digital form and the wind direction in an analog form by means of a luminous diode chain.

The combined wind sensor can be used for velocities ranging from 0.3...40 m/s. In order to prevent the formation of ice and frost during winter time use, the sensor is equipped with a electrical heater, which can be regulated with a thermostat.

The power supply unit supplies the heater with electricity.

(ii) Composition of the Instrument - The instrument consists of the following parts

:

- case

- cup anemometer

- wind vane

- connecting plug

(iii) Technical Data

Starting speed : 0.3 m/s

Maximum stress : 50 m/s

Sensitivity of response of the : 0.5 m/s wind vane at 30o deflection

Damping of the wind vane : 0.2

Measuring Range of Direction : 0...360o, 2.5o

and Resolution

Output speed : Impulses, low 0.5 V high 5 V

Output direction : 8-bit special code : low 0.5 V high 15 V Admissible Temperature Range : -35oC...+60oC

Heater : 75 W regulated by means of a thermostat

Switch-on and switch-off : 5.5oC + 3oC on, 11oC + 2.5oC off temperature

Operating voltage

Electronic : + 15 V/60 mA

Heater : 24 V/3 A

Connection : 19 pol. Euchner plug

Case material : GD-A1, sea waterproof

Transmission line : LiCY 16x0.75, max. 0 20 mm, 100 m lon

Recomm. mast dimensions : Threaded pipe 1 1/2" in accordance with

DIN 2441

Dimensions : See scale drawing (Figure-3). Wind stress at 35 m/s : Approx. 5 kp

Weight : 3.2 kg

(iv) Set-up and Mode of Operation - Wind direction is detected by means of a

highly sensitive light metal wind vane whose ball-bearing pivot is connected to a code drum. The casing of the code drum has a code pattern which can be scanned opto-electronically. The resolution of the code pattern amounts of 144 steps per 360o. An 8-bit binary information has been used i.e. the code drum has 8 scanning tracks. The Gray Code which counts up from 0...71 and down from 71...0 has been utilized. Seven tracks are required for this while the 8th track serves to differentiate between up and down. The scanning of the code pattern is carried out by means of optical reflective sensors where a diode emits an infrared ray which is reflected by the drum casing surface onto a photo-transistor. The output voltage of the transistor depends on the position of the drum (the degree of reflection). The degree of reflection of the drum background is less than of the code pattern bus is still nonzero. A drop-page of the signal voltage below the lower trigger level indicates a malfunction of the corresponding scanner component and a warning signal is given. Alternatively a potentiometer direction sensor can be used where the wind vane is coupled to a 5 K potentiometer.

Opto-electronic semiconductor components are influenced by temperature fluctuations and by ageing. Thus, the diode current in the sensor must be adjusted so as to compensate for interference. For this purpose, an additional continuous tract is scanned and the output voltage is kept constant with the regulated diode current. If, transmission factor changes due to the influences of temperature or ageing, this will be automatically taken into account and the diode current will be readjusted. Wind velocity is recorded by means of a highly sensitive rotating cup anemometer whose ball bearing pivot is connected to a slotted drum. The slotted drum is also scanned opto-electronically.

The impulse frequency emitted is proportional to wind velocity. Just as was the case for the wind direction part, the output signal of the velocity sensor is electronically monitored to ensure that there is no malfunction of the scanner. (Installation of lightning rod No. 3100.99 is recommended in areas with frequent lightning activity).

(v) Preparation for Use

(a) Selecting the Site of Operation - In general, anemometers are designed to

record wind conditions over a large area. In order to obtain comparable values for the determination of surface wind, measurements should be made at a height of 10 meters over open level terrain. Open level terrain is defined as an area where the distance between the anemometer and an obstruction amounts to at least 10 times the height of the obstruction. If, this condition cannot be met, then the anemometer should be set up at such a height where the measured values are, to the greatest extent possible, not influenced by local obstructions (approximately 6-10 meters above the obstruction).

The anemometer should be installed in the middle of flat roofs - not at the edge - in order to avoid a possible bias to one direction or the other.

(b) Installing the Cup Anemometer - Unscrew the cap nut and remove the deck

plate from the velocity sensor case. Keep the rubber sealing ring in the protective cap. Install the cup anemometer in such a manner that the dowel pin (fitting pin) in the crossarms of the cup anemometer screws into the nut in the protective cap. Replace the deck plate and rescrew the cap nut. While doing this, hold the sensor by the protective cap not by the cup.