| 摘要 |
PURPOSE:To obtain a flow rate signal whose zero point stability is excellent, by supplying external DC power or external commercial power to a flowmeter converter, and by using the period which is the common multiple times of each period of the commercial power sources having different frequencies or by using the basic clock signal which is the integer times of the period of the external commercial power source. CONSTITUTION:An external DC power source X drives a converter 7, a DC/DC converter 8 converts the power into a required DC voltage. A timing signal generating circuit 80 is constituted by the following devices: a fixed frequency oscillator 81, which outputs a basic clock whose time length is equal to the period of the common multiple times of each period of power sources with frequencies of, e.g., 50Hz and 60Hz; a frequency divider 82; and a two phase divider 83. An exciting coil 4 is driven by the output of the frequency divider 82. The output of the divider 83 is supplied to a synchronous rectifier 75. Sampling is performed under the state an output signal S of a detector 10 has reached a steady value and only during the period before the signal S is changed into the reverse direction. Therefore, a stable output signal P having small zero point fluctuation can be obtained. The converter can be constituted by utilizing an external commercial power supply and using a basic clock signal with is the integer times of the period of the commercial power source. |
