On the Comparison of Wind-velocity measured with a Pendulum-anemometer, Dines' Pressure Tube Anemometer and Robinson's Cup Anemometer

Abstract

The apparatus illustrated by Fig. I is a Pendulum-anemometer. From the experiments made by the present author it is shown that this anomometer with the plate A of 200 gram in weight and of 30cm in length, 15cm in breadth is able to be used for the measurements of wind-velocity up to 25m/s. Fig. II shows the result results obtained by the Pendulum-anemometer, compared with that obtained by the Dines' pressure tube anemometer.
As we easily notice fro_??_ Fig. 2, the Pendulum anemometer is not so good for the accurate measurements of wind-velocity, and hence it may be used only for the measurement of wind-force or so.
Now we consider the case of Dines' anemometer. Taking the mean value of the maximum wind-velocity M_x, and that of the minimum wind-velocity for M_??_, the present author defines the mean wind-velocity V_aby
Let the wind-velocity measured by the Robinson's cup anemometer be V_rm/s, the following empirical formula
betwe_??_n V_??_ and V_??_ was obtained. In the experiments made by the present author was used the secondary Robinson's cup anemometer which belongs to the Central Meteorological Observatory and several Dines' pressure tube anemometers.
If we follow the relation between V_??_ and the true air speed V:
we obtain
From this relation we easily notice that when the Dines' pressure tube anemometer is rightly used, the mean wind-velocity measured by Dines anemometer will coincide with the approximately true air speed.