Resonance circuit used for measurement device and measurement device
A resonance circuit is configured to receive a pulse density signal obtained by ΔΣ-modulating an analog displacement signal by a ΔΣ modulator and a multi-bit signal obtained from the pulse density signal and to generate an excitation signal based on the pulse density signal and the multi-bit signal. The resonance circuit includes an amplification factor controller configured to set an amplification factor depending on a vibration signal obtained from the multi-bit signal, a multiplier configured to amplify a level of the pulse density signal by the amplification factor, and a circuit group configured to generate the excitation signal based on a pulse density signal obtained by further ΔΣ-modulating an output of the multiplier. The amplification factor controller is configured to set the amplification factor using a proportional control and an integral control based a difference between an amplitude signal obtained from the vibration signal and a target amplitude value.
1. A resonance circuit used for a measurement device, configured to receive a pulse density signal obtained by ΔΣ-modulating an analog displacement signal by a ΔΣ modulator and a multi-bit signal obtained from the pulse density signal and to generate an excitation signal based on the pulse density signal and the multi-bit signal, the resonance circuit comprising:
an amplification factor controller configured to set an amplification factor depending on a vibration signal obtained from the multi-bit signal;
a multiplier configured to amplify a level of the pulse density signal by the amplification factor; and
a circuit group configured to generate the excitation signal based on a pulse density signal obtained by further ΔΣ-modulating an output of the multiplier;
wherein the amplification factor controller is configured to set the amplification factor using a proportional control and an integral control based a difference between an amplitude signal obtained from the vibration signal and a target amplitude value.
2. The resonance circuit according to claim 1 , wherein for the integral control, the amplification factor controller has a limit value to an integrated value.
3. The resonance circuit according to claim 1 , wherein for the integral control, the amplification factor controller is configured to set an integrated value to 0 if the amplitude signal exceeds a reference value.
4. The resonance circuit according to claim 2 , wherein the amplification factor controller is configured so that if the integrated value is negative, the integrated value is limited to 0.
5. The resonance circuit according to claim 1 , wherein the amplification factor controller comprises an amplifier and an integrator, the amplifier configured to amplify the difference between the amplitude signal obtained from the vibration signal and the target amplitude value, the integrator configured to integrate a value outputted from the amplifier.
6. The resonance circuit according to claim 5 , wherein the amplification factor controller further comprises another amplifier and an adder, the another amplifier configured to amplify the difference between the amplitude signal obtained from the vibration signal and the target amplitude value, the adder configured to add a value of the proportional control outputted by the another amplifier and a value of the integral control outputted by the integrator.
7. A measurement device comprising:
a detector configured to output an analog displacement signal based on displacement of an object occurred when the object is vibrated;
a ΔΣ modulator configured to ΔΣ-modulate the analog displacement signal to output a pulse density signal;
a low-pass filter configured to convert the pulse density signal to a multi-bit signal; and
a resonance circuit configured to generate an excitation signal based on the pulse density signal and the multi-bit signal, the resonance circuit comprising:
an amplification factor controller configured to set an amplification factor depending on a vibration signal obtained from the multi-bit signal;
a multiplier configured to amplify a level of the pulse density signal by the amplification factor; and
a circuit group configured to generate the excitation signal based on a pulse density signal obtained by further ΔΣ-modulating an output of the multiplier;
wherein the amplification factor controller is configured to set the amplification factor using a proportional control and an integral control based a difference between an amplitude signal obtained from the vibration signal and a target amplitude value.