The charge constant of piezoelectric material is one of the crucial constant values. At the present time, the measurement of this value is mostly realized by means of three techniques: the frequency method, the laser interferometer technique, and the quasi-static method. These techniques have been practically applied to piezoelectric ceramic samples. Our paper presents comparison of the individual methods with regard to their accuracy and the demands placed on the instrumentation and preparation of the piezoelectric material samples. A “soft” ceramic product marketed under the production code of NCE51 was used in the experiments. The methods are described in detail, including the process of sample preparation, description of the experiments, and procedure of calculating coefficients from the measured values.

The paper compares the main methods used for measuring of the piezoelectric material constants. It outlines the principle of three measuring methods most commonly used today, i.e. the frequency method, the laser interferometry method and the quasi-static method. These methods have been practically applied to piezoelectric ceramic samples. The paper describes the production of the piezoelectric ceramic samples of defined sizes in accordance with the current regulations. An NCE51 production code soft ceramic was used in the experiments. A piezoelectric charge coefficient was measured. The final values of the piezoelectric charge coefficient obtained through all the methods were compared to the catalogue values of the piezoelectric ceramic. All three methods can be described as appropriate; compared with the frequency method, the laser interferometry and quasi-static methods are rather time-consuming and more demanding with respect to preparation of the measurement experiment. The frequency method provides results within a smaller value range.

This paper presents a simple method for compensating the Sagnac phase shift in an interferometric fiber-optic gyroscope (I-FOG) with a piezoelectric modulator. The common advantages of I-FOGs with closed-loop compensation are linearized output characteristics and insensitivity to the light source power, including its time and thermal-induced fluctuations. Whereas closed-loop operation is normally achieved via ramp modulation requiring an electro-optic modulator, all-fiber architectures with a piezoelectric modulator are mostly limited to open loop. Nevertheless, such setups can more conveniently utilize a less expensive single-mode fiber with depolarized light and do not require any custom-made components. The proposed method allows us to combine the advantages of both approaches. Closed-loop compensation is ensured by adding further sinusoidal modulation to the common biasing modulation, such that the Sagnac phase shift is compensated solely at the sampling instants. We describe and experimentally demonstrate the proposed approach, utilizing a test setup to compare our closed-loop solution with open-loop operation. The results denote that the method provides a cost-efficient manner of performance improvement compared to the open-loop I-FOGs based on a piezoelectric modulator.

This article describes in detail the measurement method and the calculation of the complete matrix of piezoelectric coefficients from one PZT ceramics disc. A set of piezoelectric samples is produced from a disc of appropriate dimensions for all types of vibrations that comply with the world and the European standards. The samples produced are a thin plate for traverse length mode, a thin disc for radial mode and thickness extension mode, a cylinder for longitudinal length mode and a thin plate for thickness shear mode. Soft PZT ceramics, type NCE51, was used for calculation of the matrix coefficient and for description of the measurement method. Frequency method was used for the measurements and for the calculation of all coefficients. Impedance analyzer Agilent 4294A with a range from 40 Hz to 110 MHz and measuring tweezers “Tweezers Contact Test Fixture 16334A” were used for the measurements. The experiments verified the possibility of determining the complete matrix of the coefficients on piezoelectric ceramics without major requirements regarding the set of samples needed for the measurement.

Measuring the efficiency of piezo energy harvesters (PEHs) according to the definition constitutes a challenging task. The power consumption is often established in a simplified manner, by ignoring the mechanical losses and focusing exclusively on the mechanical power of the PEH. Generally, the input power is calculated from the PEH’s parameters. To improve the procedure, we have designed a method exploiting a measurement system that can directly establish the definition-based efficiency for different vibration amplitudes, frequencies, and resistance loads. Importantly, the parameters of the PEH need not be known. The input power is determined from the vibration source; therefore, the method is suitable for comparing different types of PEHs. The novel system exhibits a combined absolute uncertainty of less than 0.5% and allows quantifying the losses. The approach was tested with two commercially available PEHs, namely, a lead zirconate titanate (PZT) MIDE PPA-1011 and a polyvinylidene fluoride (PVDF) TE LDTM-028K. To facilitate comparison with the proposed efficiency, we calculated and measured the quantity also by using one of the standard options (simplified efficiency). The standard concept yields higher values, especially in PVDFs. The difference arises from the device’s low stiffness, which produces high displacement that is proportional to the losses. Simultaneously, the insufficient stiffness markedly reduces the PEH’s mechanical power. This effect cannot be detected via the standard techniques. We identified the main sources of loss in the damping of the movement by the surrounding air and thermal losses. The latter source is caused by internal and interlayer friction.