Thermal type flow meter
AssigneeHitachi Automotive Systems, Ltd.
InventorsRyo Ando, Daisuke Terada, Takeo Hosokawa
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Abstract
A thermal-type flow meter for representing a flow rate of air by the frequency of a periodic signal, wherein abnormalities in the waveform of an output signal due to frequency variation is prevented while high-frequency noise is suppressed. The thermal-type flow meter pertaining to the present invention is provided with a plurality of switching elements connected in parallel, and varies a delay width between the switching elements in accordance with variation of the frequency of a periodic signal for representing a flow rate.
Claims10
A thermal-type flow meter at outputs an output signal indicating a flow rate of air using a frequency, comprising:
- a signal generator that generates a periodic signal indicating the flow rate using a frequency;
- a shunt circuit that is configured by a plurality of switching elements connected in parallel, and outputs the output signal corresponding to the periodic signal;
- and
- a delay circuit that delays an operation timing of each switching element such that the respective switching elements are turned on at different phases of the periodic signal,
- wherein the shunt circuit is configured to lower a signal level of the output signal from a high level in a stepwise shape whenever each switching element is turned on, and to make the signal level of the output signal fall to a low level when all the switching elements are turned on, and
- wherein the delay circuit changes the delayed time duration to be shortened as the frequency of the periodic signal is increased, and changes the delayed time duration to be lengthened as the frequency of the periodic signal is decreased.
Dependencies are inferred from the claim text.