Load sensor
AssigneePanasonic Corporation
InventorKOUMEI FUJITA
Life of this patent
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Abstract
A load sensor includes a vibrator, a drive electrode provided at the vibrator, a drive circuit that supplies, to the drive electrode, a drive voltage for vibrating the vibrator, a detection electrode that outputs a current in response to a vibration of the vibrator, and an IV converter that converts the current output from the detection electrode into a voltage. The drive circuit includes an operational amplifier that outputs the drive voltage and a resistor connected to the operational amplifier. The drive circuit has a small internal resistance. The IV converter has an inverted input terminal that is virtually grounded and that has the current input thereto. The IV converter may constitute a negative feedback circuit.
Claims4
A load sensor comprising:
- a vibrator;
- a drive electrode provided at the vibrator;
- a drive circuit that supplies, to the drive electrode, a drive voltage for vibrating the vibrator;
- a detection electrode that outputs a current in response to vibration of the vibrator;
- and
- an IV converter that converts the current output from the detection electrode into a voltage and outputs the voltage as an output signal,
- wherein the drive circuit includes an operational amplifier that outputs the drive voltage,
- wherein the drive circuit generates the drive voltage based on the output signal, and
- wherein internal resistance R1 (Ω) of the operational amplifier, angular frequency ω (rad/sec) of the drive voltage, allowable phase difference φ (degrees), and capacitance C (F) of the drive electrode satisfy a formula:
- R1≦−(1/ωC)×tan(φ×(π/180)).
Dependencies are inferred from the claim text.