77 results about "Measurement frequency" patented technology

The invention relates to an impedance measurement method and system. The method comprises the following steps: acquiring grid-connected point voltage, measurement frequency, disturbance amplitude and nth inverter grid-connected current of the multi-inverter grid-connected system; inputting the grid-connected point voltage into an improved phase-locked loop in a fundamental wave and disturbance control unit to generate a power grid frequency and a power grid phase; inputting the power grid phase and the nth inverter grid-connected current into the current control loop to generate a fundamental current control instruction; inputting the measurement frequency, the disturbance amplitude and the power grid frequency into the disturbance control ring to generate a disturbance instruction; inputting the disturbance instruction and the fundamental current control instruction into the modulation ring, generating a control driving signal according to a modulation strategy of an inverter, and controlling each inverter switch; and obtaining the controlled grid-connected point voltage through an impedance calculation unit, and generating the impedance of the inverter to be tested and the impedance of the power grid. By adopting the method, disturbance can be injected efficiently at low cost so as to measure impedance.

The invention discloses a self-adaptive metering method of an ultrasonic water meter, which relates to the field of water meter metering, and comprises the following steps: acquiring real-time water temperature data and real-time flow velocity data of a measured fluid, compensating the sound velocity of ultrasonic waves based on the real-time water temperature data to obtain a first compensated sound velocity, based on the first compensation sound velocity, an excitation voltage self-adaptive adjustment strategy with ultrasonic wave head-wave ratio regulation and control and a measurement frequency dynamic regulation and control strategy are executed, secondary compensation is conducted through a built error curved surface compensation model with the water temperature and the flow velocity as indexes, and the initial flow value is corrected through an error compensation value; by means of multi-parameter collaborative real-time optimization, high-precision measurement and low-power-consumption operation under all working conditions are achieved, the measurement precision in the full-scale and full-temperature range is remarkably improved, and by intelligently adjusting the measurement frequency, cooperating with the flow rate change rate and error model feedback and dynamically balancing the dynamic response speed and static power consumption, the measurement precision is improved. And finally, double optimization of precision and energy efficiency is achieved.

The invention belongs to the technical field of underwater target radiation noise measurement, and particularly relates to a sparse combination array measurement system and method for underwater target radiation noise measurement, a program and a storage medium. A sparse combined array formed by a sound pressure spiral double-cone volume array with a sparse structure and a sound pressure vector nested vertical linear array is designed, a combined array frequency-division testing scheme of a high-frequency volume array and a low-frequency vertical linear array is adopted, a combined measurement method of a sound pressure hydrophone and a vector hydrophone is utilized, a measurement frequency band is extended, and the measurement precision is improved. And effective measurement of the full-band radiation noise of the underwater target is realized. Through a sparse array arrangement structure and an improved constant-beam-width beam forming method, a two-dimensional steady constant-beam-width beam is obtained while the number of array elements is reduced and the array complexity is reduced, and an appropriate main lobe width and a lower side lobe level can be adjusted according to a measured target and a measurement distance. According to the method, the array element redundancy of the measurement array is reduced, and the method can be flexibly applied to various application scenes of underwater radiation noise measurement.

The invention relates to a height measurement method and device based on a multi-frequency linear combination InSAR and a storage medium, and the method comprises the steps: carrying out the segmentation of a used large-bandwidth signal, so as to extract different center frequencies, carrying out the linear combination of the center frequencies, so as to generate a plurality of synthesized measurement frequencies, measurement is carried out based on all measurement frequencies from small to large, a measurement phase difference of a next measurement result is updated based on a product invariant principle by utilizing a result of a previous measurement frequency, phase unwrapping is guided step by step through hierarchical classification, and the highest precision is achieved. According to the method, the maximum measurement range and the highest measurement precision of the extreme steep terrain (EST) are achieved at the same time, real-time measurement is achieved through single-time large-bandwidth signal collection, no time error exists, and meanwhile the large bandwidth provides excellent distance resolution.

The invention relates to a multi-source micro-grid inertial support detection method and device and a storage medium. The method comprises the steps that S1, a discretized original voltage sequential sequence and a discretized original current sequential sequence are collected; s2, respectively extracting a first voltage sequence and a first current sequence corresponding to a measurement moment based on the original voltage sequential sequence and the original current sequential sequence; s3, obtaining a measurement frequency and a voltage and current phase difference based on the first voltage sequence and the first current sequence, and obtaining an active power based on the voltage and current phase difference; s4, obtaining a reference frequency and a reference power based on the measurement frequencies and the active powers at the plurality of measurement moments; and S5, based on the reference frequency and the reference power, combining the measurement frequency and the active power at the measurement moment to obtain the equivalent inertia. Compared with the prior art, the method has the advantages that the measurement accuracy of the equivalent inertia in the multi-source micro-grid environment is improved, and the like.

The invention provides a flow velocity meter and a frequency adaptive adjustment method thereof, and the method comprises the steps: determining an effective frequency bandwidth of flow velocity data under a current working condition through obtaining the flow velocity data collected by a flow velocity sensor; calculating the target sampling frequency of the flow velocity meter based on the effective frequency bandwidth and the flow state change period of the medium in the water resource treatment pipeline; the current flow state category and the working condition stability level are judged based on the collected temperature, pressure and flow combined change characteristics; finally, the target sampling frequency is adjusted according to the current flow state category, the frequency adjustment amplitude is enhanced according to the working condition stability level, the adjusted sampling frequency serves as the measurement frequency of the flow meter to be output, and the steps are periodically repeated to achieve self-adaptive updating of the measurement frequency. According to the scheme, adaptive optimization of the measurement frequency can be realized, and the measurement precision is improved.

The invention discloses an underwater pore medium stratum bubble size calculation method, and relates to the technical field of underwater pore medium stratum geophysical exploration, and the method comprises the following steps: S1, obtaining rock physical parameters of an underwater stratum to be detected; s2, a sound wave transmitting transducer and a receiver are deployed at a point to be measured, the sound wave transmitting transducer transmits a set signal to determine a measurement frequency range, and the receiver records a sound wave speed and an attenuation coefficient of each frequency point; s3, judging whether adjacent frequency points meeting the requirements of sound wave speed reduction and attenuation coefficient increase exist or not, and if yes, re-measuring and extracting the sound wave speed and attenuation coefficient corresponding to the bubble resonance characteristics; otherwise, recording the bubble-free characteristic times, and if the times do not reach the threshold value, continuing to adjust the number of the frequency points and returning to the step 2; s4, constructing a target function; and S5, under the condition that the angular frequency and the sound wave speed are known, solving the independent variable, the bubble radius and the bubble saturation which enable the objective function to be minimum, and determining the final bubble size and saturation.

The invention discloses an island detection method, system and device based on multiple parameters and a storage medium, and the key points of the technical scheme are that the method comprises the steps: carrying out the sampling of a grid connection point of a distributed power supply, and obtaining a voltage signal and a current signal; calculating to obtain a phase angle change rate according to the voltage signal and the current signal, and calculating to obtain a measurement frequency, a frequency change rate and a voltage change rate according to the voltage signal; obtaining an intermediate judgment result according to the measurement frequency and the frequency change rate; and judging whether an island occurs or not according to the intermediate judgment result, the voltage change rate and the phase angle change rate. According to the invention, missed judgment and misjudgment are reduced, and safe and efficient detection is maintained in an actual island state.

A self-adaptive joint control three-dimensional ocean current measurement and environment self-compensation method comprises the following steps: setting initial weight coefficients of four acoustic axes to be the same, receiving echo information according to a transducer, carrying out self-adaptive gain adjustment on a signal echo amplitude, calculating a re-allocation weight coefficient of joint debugging of each acoustic axis according to a gain change, and carrying out self-adaptive compensation on the self-allocation weight coefficient of the joint debugging of each acoustic axis; real-time measurement variance calculation and measurement frequency self-adaptive adjustment are carried out, joint debugging calculation is carried out again to obtain an optimized weight, a sound axis used for three-dimensional flow velocity calculation is obtained through redundancy elimination, and finally temperature and pressure compensation correction is carried out according to the obtained sound axis to obtain a flow velocity calculation result. The method has the advantages that the real-time performance of flow measurement is better, the overall coordination of a measurement system is better, the response of measurement is more flexible, the self-adaptive capability is high, and accurate and stable measurement results can be provided under various environmental conditions.

The invention provides a system for analysing vocal signals from an individual, said system comprising an acoustic sensor configured to have a measured frequency response in the ultrasonic range; mean

A frequency response measuring device according to one aspect of the present disclosure measures the frequency response characteristics of the output of a motor with respect to a command from a motor control device in a drive system with a feed axis that moves a movable body within a predetermined movable range, a motor that drives the feed axis, and a motor control device that controls the motor, wherein the frequency response measuring device comprises: an information acquisition unit that acquires setting information, including a condition for measuring the frequency response characteristics and a drive range, as well as operating information that indicates an operating state of the motor and the motor control device; a vibration command generation unit that generates a vibration command that drives the motor back and forth by input into the motor control device;a basic velocity command generation unit that generates a basic velocity command to drive the motor at a speed at which the moving body does not deviate from the drive range before the input of the vibration command is completed by being entered into the motor control device; and a frequency response calculation unit that calculates the frequency response characteristics based on the operating information and the vibration command.

A method of determining a filling level of a product in a tank, comprising the steps of: generating an electromagnetic transmit signal exhibiting a measurement sweep across a time series of piece-wise constant frequencies being within a measurement frequency range starting at a first frequency, and ending at a second frequency higher than the first frequency, a difference between frequencies in each pair of adjacent frequencies in the frequency range being equal to the first frequency; guiding the transmit signal towards and into the product in the tank; guiding an electromagnetic reflection signal back towards the transceiver; mixing the reflection signal with an electromagnetic reference signal, resulting in a mixer output indicative of a difference between the reflection signal and the reference signal; forming a measurement signal based on the mixer output; and determining the filling level based on the measurement signal.

The invention relates to the technical field of noise deafness susceptibility grading, in particular to a noise deafness susceptibility grading method and system based on a multi-band hearing threshold, and the method comprises the steps: presetting measurement frequency points, generating a measurement frequency point set according to a sequence from high frequency to low frequency, and completing M times of independent measurement for each frequency point; recording a tested subjective response timestamp, and generating a confidence value label; an otoacoustic emission signal in a tested ear canal is collected in real time, a time domain signal with the highest confidence coefficient of a single frequency point is extracted, spectrum features are calculated, and otoacoustic emission joint parameters are constructed. According to the method, the time sequence diffusion rule from high frequency to low and medium frequency hair cell damage can be comprehensively captured, the identification accuracy of potential auditory impairment is remarkably improved, the propagation mechanism from high frequency damage to intermediate frequency can be simulated by constructing the physically constrained spectrum migration operator, and otoacoustic emission time domain-frequency domain joint parameters and physiological indexes are combined, so that the identification accuracy of the potential auditory impairment is improved. And individualized and dynamic injury risk prediction is realized.

The utility model discloses a sample vibration suppression structure and an alternating gradient magnetometer, and relates to the technical field of mechanical vibration suppression, the sample vibration suppression structure comprises a support assembly and a sample suspension structure mounted on the support assembly; the sample suspension structure comprises an elastic vibration isolation unit and a sample support connected with the elastic vibration isolation unit, the sample support is used for bearing a sample in the magnetic field action area, and the elastic vibration isolation unit is used for attenuating vibration transmission from the supporting assembly to the sample support. The elastic vibration isolation unit can isolate vibration near the measurement frequency and larger than the measurement frequency, so that vibration noise can be weakened, and the influence of the vibration noise on magnetic measurement is reduced; according to the structure, a complex active vibration isolation control system does not need to be additionally arranged, passive vibration isolation is achieved through pure mechanical elastic design, the equipment cost and energy consumption are reduced, and electronic interference possibly introduced by the active vibration isolation system is avoided.

The invention relates to a consistency evaluation method for dynamic performance indexes of a multi-dimensional force sensor. Time-frequency domain dynamic performance indexes of the multi-dimensional force sensor are calculated on the basis of a frequency response function of the multi-dimensional force sensor. In the aspect of frequency domain performance indexes, a measurement frequency band and a response frequency band are analyzed and calculated by adopting a threshold comparison method according to an amplitude-frequency curve of each main channel of a sensor frequency response function, and modal parameters in the response frequency band are analyzed and calculated by adopting a peak search method and a step-by-step integral iteration method; in the aspect of time domain performance indexes, an inverse Fourier transform method is adopted to convert a frequency response function of each main channel and an inter-dimension coupling channel of the sensor into a time domain unit impact response, and the time domain unit impact response is directly subjected to linear convolution with a constructed unit step signal to reconstruct a unit step response of each channel of the sensor; step response rise time and adjustment time of each main channel are analyzed and calculated by adopting a threshold comparison method, and step response overshoot of the main channel and a dimensional dynamic coupling error of each coupling channel are analyzed and calculated by adopting a peak search and range conversion method; finally, the problem that the dynamic performance index evaluation of the existing multi-dimensional force sensor is incomplete under the finite dynamic calibration test condition is effectively solved.

To provide a measuring device capable of improving measurement accuracy.SOLUTION: A measuring device 10 includes: a ring-shaped transmission line 110; a first ground layer 121; a second ground layer 122; a first dielectric layer 130; a second dielectric layer 140; a pair of power supply terminals 161 and 162 for supplying the power to the transmission line 110; and a plurality of ground terminals that electrically connect the first ground layer 121 and the second ground layer 122. The first dielectric layer 130 has a cavity 131 for placing a measurement object. In the planar view, the power supply terminals 161 and 162 are located at the intersection points of the straight line L1x and the transmission line 110, respectively. The plurality of ground terminals includes ground terminals 171a, 172a, 173a, and 174a. The spacing between each of the ground terminal 171a and the ground terminal 172a and the power supply terminal 161, and the spacing between ground terminal 173a and 174a and each of the power supply terminals 162, are both one-quarter or less of the wavelength corresponding to the highest frequency in the measurement frequency band.SELECTED DRAWING: Figure 4

The application discloses a kind of self-adapting metering methods of ultrasonic water meter, it is related to water meter measurement field, comprising the following steps, obtain the real-time water temperature data and real-time flow rate data of measured fluid, the sound velocity of ultrasonic wave is compensated based on real-time water temperature data, obtain first compensation sound velocity, and based on first compensation sound velocity, execute the excitation voltage self-adapting adjustment strategy with the measurement frequency dynamic control strategy with the first wave ratio control of ultrasonic wave, utilize the error surface compensation model indexed with water temperature and flow rate constructed to carry out secondary compensation, and utilize error compensation value to correct initial flow value, the application realizes high-precision measurement and low-power operation in full operating condition by multi-parameter collaborative real-time optimization, significantly improve the measurement accuracy of full range, full temperature range, by intelligent adjustment measurement frequency, collaborative flow rate change rate and error model feedback, dynamic balance dynamic response speed and static power consumption, finally achieve the dual optimization of precision and energy efficiency.

A power line grounding line detection method and apparatus. The method comprises: measuring a first impedance of a power line at a first measurement frequency, and measuring a second impedance of the power line at a second measurement frequency (S101); on the basis of the first measurement frequency and the first impedance corresponding thereto, and the second measurement frequency, and on the basis of the second impedance corresponding thereto, determining an impedance property of the power line (S102); calculating a third impedance of the power line on the basis of the impedance property of the power line, and calculating a reactance factor on the basis of the third impedance (S103); obtaining a grounding line installation state of the power line on the basis of the reactance factor, the third impedance, and the impedance property (S104). The present method resolves the technical problems in the prior art of low detection accuracy and insufficient validity, which make relatively large errors likely, causing detection faults.

The application discloses a frequency anti-misoperation method and system based on wide-area low-frequency centralized pump cutting, and the method comprises the following steps: receiving the frequency of operating equipment sent by each transformer substation or energy storage power plant; starting a low-frequency centralized control device if the frequency of any current operating equipment is less than or equal to a starting frequency; calculating a frequency comprehensive value of the operating equipment, and determining a measured frequency of the low-frequency centralized control device; and cutting the pump load of each energy storage power plant according to a preset pump cutting number when the measured frequency is lower than a preset action frequency and reaches an action delay. The frequency anti-misoperation method based on wide-area low-frequency centralized pump cutting can effectively realize frequency anti-misoperation by means of the frequency of operating equipment of different power plants and substations, so that the stability of the power system is maintained.

A method for operating an ultrasonic flowmeter for measuring a flow through a measuring tube. A control and evaluation unit controls the emitting ultrasonic transducer such that it emits the ultrasonic signal. A receiving ultrasonic transducer receives the emitted ultrasonic signal and the control and evaluation unit in the measuring operation by evaluating emitted and received ultrasonic signals. At least one indirect value for the flow rate of the medium through the measuring tube is determined from a determined signal transit time of the ultrasonic signal. The method can react flexibly to changing measurement conditions in that the control and evaluation unit controls the emitting ultrasonic transducer such that a broadband ultrasonic signal is emitted. An optimum measuring frequency range is determined in an evaluation step. The received broadband ultrasonic signal is frequency filtered into a plurality of measuring frequency ranges of the received broadband ultrasonic signal.

The invention relates to the technical field of electric vehicle motor control, and discloses an electric vehicle motor speed limit control method and device based on edge calculation. The method comprises the following steps: acquiring motor rotating speed data in real time through a sensor, and analyzing by adopting a fast Fourier transform algorithm to obtain time interval distribution characteristics; the rotating speed data is smoothed through an adaptive filtering algorithm, and the measurement frequency is adjusted to optimize the data acquisition precision; and extracting and classifying rotating speed amplitude interval characteristics by using a k-means clustering algorithm, and dynamically adjusting speed limit control parameters of the motor based on an amplitude interval distribution rule. A motor control instruction is calculated and updated in real time through the edge calculation platform so as to realize adaptive adjustment of the working condition of the motor; and the real-time feedback data is used for further optimizing a motor operation model, dynamically adjusting a control instruction and ensuring the stable and accurate operation of the electric vehicle under different working conditions. According to the invention, the dynamic response capability and energy efficiency of the motor of the electric vehicle are improved, and the safety and high efficiency under various working conditions are ensured.

The present invention discloses a strain piezoelectric composite rotor balance, belonging to the technical field of wind tunnel tests; it includes a floating frame, a fixed frame and a force-sensitive unit; the force-sensitive unit is arranged between the floating frame and the fixed frame; the force-sensitive unit is provided with a strain force sensor, a piezoelectric force sensor, a decoupling link and a slider capable of adjusting the pre-tightening force; this solution uses the characteristics of high static measurement accuracy of the strain force sensor and wide dynamic measurement frequency band of the piezoelectric force sensor, as well as the decoupling effect of the decoupling link to achieve simultaneous high-precision measurement of the static load and high-frequency vibration load of the rotor.

The application relates to the technical field of acoustic measurement, and particularly provides a low-frequency acoustic parameter measurement method and device. The method comprises the following steps: acquiring a first measurement sound pressure corresponding to a first cavity and a second measurement sound pressure corresponding to a second cavity under a first measurement condition; the first cavity and the second cavity are separated by an excitation piece; the first measurement condition comprises that the first cavity and the second cavity are isothermal; the measurement frequency range of the first cavity and the second cavity is a first target low-frequency frequency range; and a sample to be measured is arranged in the first cavity; a first sound pressure transfer function is obtained by calculating according to the first measurement sound pressure and the second measurement sound pressure; and a target acoustic parameter corresponding to the sample to be measured is obtained by calculating according to the first sound pressure transfer function, a first volume of the first cavity and a second volume of the second cavity. The low-frequency acoustic parameter measurement method and device accurately and efficiently obtain the target acoustic parameter of the sample to be measured under the isothermal low-frequency condition.

The present invention discloses a method for calculating the bubble size of an underwater pore medium formation, which relates to the technical field of geophysical exploration of underwater pore medium formations, and includes: S1, obtaining the petrophysical parameters of the underwater formation to be measured; S2, deploying a sound wave transmitting transducer and a receiver at the measurement point, the sound wave transmitting transducer emits a set signal to determine the measurement frequency range, and the receiver records the sound wave velocity and attenuation coefficient at each frequency point; S3, determining whether there are adjacent frequency points that satisfy the condition that the sound wave velocity decreases and the attenuation coefficient increases. If so, re-measure and extract the sound wave velocity and attenuation coefficient corresponding to the bubble resonance characteristics; otherwise, record the number of times without bubble characteristics. If the number of times does not reach the threshold, continue to adjust the number of frequency points and then return to step 2; S4, constructing an objective function; S5, under the condition that the angular frequency and the sound wave velocity are known, solving the independent variable, bubble radius and bubble saturation that minimize the objective function, and determining the final bubble size and saturation.

Method for adapting operation settings for a frequency sweep measurement of a polymer product, the method comprising the steps of: providing (S1) at least one set of operation setting parameters comprising at least one frequency range for the frequency sweep measurement of the polymer product, the at least one frequency range comprising a plurality of specific measurement frequencies; optimizing (S2) the frequency range by deleting at least one measurement frequency of the plurality of specific measurement frequencies within a lower half of the frequency range resulting in a first optimized frequency range; and optimizing (S3) the first optimized frequency range by determining a value of measurement frequencies present per decade of frequency within at least a subrange of the frequency range and reducing the determined value of measurement frequencies present per decade within the at least one subrange of the frequency range by deleting at least one measurement frequency of the at least one subrange resulting in a second optimized frequency range.

A computer-readable storage device stores machine instructions which, when executed by one or more central processing unit (CPU) cores, causes the one or more CPU cores to use a first ultrasonic transducer and a second ultrasonic transducer to measure fluid flow using a current measurement frequency and to perform a temperature calibration process. The temperature calibration process includes the sequentially generation of a plurality of electrical signals for the first ultrasonic transducer, the generated electrical signals each having a different frequency. For each frequency, the temperature calibration process includes the measurement of an amplitude of a signal from the second ultrasonic transducer. Based on the measured amplitudes of the signals from the second ultrasonic transducer, the temperature calibration process includes the determination of a new measurement frequency. The first and second ultrasonic transducers are used to measure fluid flow using the new measurement frequency.

The present application relates to a kind of frequency division multiplexing biological impedance multi-frequency measurement system and method.The method is aimed at the frequency range of biological tissue impedance change, the problem that excitation signal and response signal are difficult to sample in whole cycle in actual measurement is solved, and the accuracy of biological tissue impedance measurement is improved.Using the OFDM frequency division multiplexing idea minimizes crest factor, uses grouping search algorithm to optimize the phase at each excitation frequency, reduces peak factor, and improves signal-to-noise ratio;And an adaptive dynamic synchronous sampling rate adjustment method combined with window function optimization is proposed, which realizes whole cycle sampling and makes the optimal scheme of Fourier change spectrum resolution to fall in the measurement frequency range, and improves the measurement accuracy.

The present invention discloses a low-frequency acoustic tube measurement method for the vibration velocity transfer coefficient of underwater acoustic materials, which includes the following steps. Step 1: The low-frequency acoustic tube is placed vertically, and a transmitting transducer is installed at its bottom. Two hydrophones are embedded in the low-frequency acoustic tube wall at intervals, and the low-frequency acoustic tube is filled with degassed water medium. Step 2: The underwater acoustic material to be measured is placed in the low-frequency acoustic tube and located on the water surface. The gap between the underwater acoustic material to be measured and the low-frequency acoustic tube wall is filled with water medium, and the upper surface of the underwater acoustic material to be measured is a rigid backing. An accelerometer is installed on the rigid backing, and a cavity is provided between the rigid backing and the upper cover of the low-frequency acoustic tube. The present invention realizes the measurement of the vibration characteristic parameters of the underwater acoustic material sample in the low-frequency acoustic tube, can fully simulate the working conditions of the sample in actual work and the structure of the submarine acoustic covering layer, and the measurement frequency band is concentrated in the range of 100 Hz to 1 kHz where it is difficult to reduce vibration and noise in submarine shock absorption technology.

The present invention relates to a multi-source microgrid inertial support detection method, device, and storage medium. The method comprises: step S1: collecting discretized original voltage and current time series; step S2: extracting first voltage and current sequences corresponding to the measurement moments based on the original voltage and current time series; step S3: obtaining a measured frequency and a voltage-current phase difference based on the first voltage and current sequences, and obtaining active power based on the voltage-current phase difference; step S4: obtaining a reference frequency and a reference power based on the measured frequencies and active powers at multiple measurement moments; and step S5: obtaining equivalent inertia based on the reference frequency and reference power, combined with the measured frequency and active power at the measurement moment. Compared with the prior art, the present invention has advantages such as improved measurement accuracy of equivalent inertia in a multi-source microgrid environment.

Using a capacitance sensor may include taking a first noise measurement by imposing a first signal on a capacitance sensor, the first signal having a first frequency; taking a second noise measurement by imposing a second signal on the capacitance sensor, the second signal having a second frequency different than the first frequency; determining the measurement with the lower amount of noise between the first noise measurement and the second noise measurement; and taking a capacitance measurement by imposing a third signal on the capacitance sensor, the third signal having either the first frequency or the second frequency based, at least in part, on the frequency of the measurement with the lower amount of noise.