| 摘要 |
PURPOSE:To make the current meter inexpensive by obtaining the propagation time of ultrasonic waves by using the two clock signals of which the periods vary slightly with each other in a time measuring circuit. CONSTITUTION:A time measuring circuit 7a is provided with the 1st clock signal generator 15 which receives the pulse signal from a pulse generator 1 and generates the 1st clock signal in synchronization with this and the 2nd clock signal generator 17 which receives the pulse signal from a discriminator 6 and generates the 2nd clock signal. These are so constituted that the generation times of both clock pulses from the time when the generation times of the clock pulses of these two clock signals coincide are counted by a counter 18 and are operated by an arithmetic circuit 20, whereby the propagation time of ultrasonic waves is obtained. These result in the relatively lower frequencies of the clock signals and reduced cost of the clock pulse transmitters, etc. thereby enabling the overall reduction in the cost of the current meter. |
