Fundamental and Experimental Studies on Grain Sorting by Means of Air Stream (I)

Trial Manufacture of Hot-wire Anemometer

Abstract

(1) In order to survey the distribution of mean wind velocity and intensity of turbulence in the winnower, a set of recordihg hot wire anemometer is built.
(2) The anemometer consists of a pair of platinum hot wire with the diameter of 0.025mm, a bridge circuit, a D-C amplifier and a recorder.
(3) The measurement of mean wind velocily is done by means of so called constant resistance method, and the turbulence by constant current method.
(4) A calibrating wind tunnel, composed of a fan, guide tunnels, an orifice, a tapered tunnel, a measuring tunnel and a strainer, is constructed to calibrate the anemometer.
Calibration is performed by comparing the reading of the anemometer with that of the pressure difference led from the orifice, which had already been calibrated by comparing with the standard Pitot-static tube.
(5) The reading of mean wind velocity gotten by the anemometer may include the error estimated as 2.5%.
(6) The altitude of output may include the error evaluated as 4.0% caused by the imperfection of the compensation to the characteristics of hot wire, when frequency of turbulence is 50c/s.
(7) The error derived from the non-linierity may occur if the altitude of turbulence grows more thon ±0.7m/s.
(8) The pen-writng oscillograph is employed for the reason of the convenience of handling. In this case if the error which amounts to ±10% is permissible, the frequency range of DC-50c/s is measurable.