| 摘要 |
PROBLEM TO BE SOLVED: To provide a liquid dispenser and a digital liquid dispenser having high flow accuracy with a small number of part items, capable of controlling a micro quantity of fluid and easily controlling the jet quantity of the micro quantity of fluid in a wide range from the micro quantity of fluid in the minimum unit. SOLUTION: This liquid dispenser is provided with two chambers 2M, 2R comprising pressure chambers 22 and piezoelectric elements 31 for pressurizing or decompressing a fluid 1. One chamber serwes as an empty chamber (a reference chamber) 2R, and the other chamber as a measuring chamber 2M to receive the supply of the fluid 1 and to convey the fluid 1 by the excitation of the piezoelectric element 31. In detecting pressure received by the measuring chamber 2M from the fluid 1, a first capacitor C1 series-connected to the piezoelectric element 31 (Cm) of the measuring chamber 2M, and a second capacitor C2 series-connected to the piezoelectric element 31 (Cr) of the reference chamber 2R are connected in parallel to constitute a bridge circuit. An exciting power source 4 is connected in parallel to the bridge circuit to excite the piezoelectric elements 31 (Cr, Cm), and the differential voltage of the bridge circuit is amplified by an arithmetic amplifier 5.
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