| 摘要 |
PROBLEM TO BE SOLVED: To suppress the lowering of an ultrasonic output from a transmission side transducer due to a variation in the pulse width of one-shot circuits caused by the lowering of a battery voltage in an ultrasonic flowmeter. SOLUTION: In a normal measurement mode, a mode selection signal is set to L level. Each time a trigger pulse is emitted from an OR gate, output pulses from the one-shot circuits 11 and 12 drive the transmission side transducer 1 to obtain a flow velocity and flow rate with a time required for reaching a receiving side transducer which is not shown. The selection signal is intermittently set to H level to obtain a check mode. Gates 20 and 22 are closed, a gate 21 is opened, and both circuits 11 and 12 are connected to each other in loop shape to form a transmitter. The optimum resistances of resistors R1 to R4 are selected with analog switches 11A and 12A and a variation in pulse width due to the lowering of voltage is corrected. COPYRIGHT: (C)2004,JPO&NCIPI
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