Described is a device which converts the volumetric flow to the pulse signal with the recurrency frequency proportional to the volumetric flow rate. The device is composed of a magnetic flow transmitter and a drag cup type induction tachometer. Through the experiments, the shaft speed of the induction tachometer very accurately and quickly followed up A. C. signals transmitted from the magnetic flow transmitter, by means of the feedback control technique; where the shaft rotation generates the pulse signal in a simple optical way.
The output errors of the induction tachometer due to frequency change of the source supply and ambient temperature change have been successfully reduced by a new methode without using any additional compensating systems. Besides, the qua drature fundamental noises coming from the magnetic flow transmitter and the induction tachometer have been automatically eliminated from the high gain amplifier by using a circuitry of several siliconcarbide varistors.
The device combined with a magnetic flow transmitter of 600 mm. inner diameter was tested for eighteen cases of water flow experiments and the difference between the value of total flow measured directly and that indicated by this device was always less than 0.5%.
