1. Nonlinear

Piezoelectric sensorThe amplitude linearity refers to the degree of change in sensitivity of the measured physical quantity (such as force, pressure, acceleration, etc.) as it increases. Taking piezoelectric accelerometer as an example, illustrate the linearity of amplitude.Piezoelectric accelerometerThe theoretical lower limit of the linear range of amplitude can reach 0, but due to the influence of non vibration environments and the limitation of noise levels in secondary instruments (charge amplifiers, impedance converters), only high-sensitivity piezoelectric acceleration sensors can be used to measure small accelerations.

2. Lateral sensitivity

Piezoelectric accelerometerThe reasons for the generation of lateral sensitivity include: insufficient machining accuracy; Insufficient assembly accuracy; During the assembly process, the purification conditions were insufficient, and dust, impurities, and other contaminants contaminated the sensor components, resulting in severe deviations; And the piezoelectric conversion element itself has defects, such as insufficient cutting accuracy and inconsistent piezoelectric constants in various parts of the piezoelectric conversion element. The lateral sensitivity ratio index reflects the inherent quality defects of a piezoelectric sensor, and it is an extremely important technical indicator for measuring the quality of a sensor.Piezoelectric accelerometerThe lateral sensitivity is directional. When assembling sensors, as long as the mutual positions of each piezoelectric conversion element are carefully adjusted, mutual compensation can be achieved, resulting in a decrease in lateral sensitivity.

3. The impact of environmental temperature

The change in environmental temperature has a significant impact on the piezoelectric constant and dielectric constant of piezoelectric materials, which will cause changes in sensor sensitivity. The degree of temperature effect varies depending on the piezoelectric material used. When the temperature is below 400 ° C, its piezoelectric constant and dielectric constant are stable.

The Influence of Temperature on Artificially Polarized Piezoelectric CeramicsquartzIt is much larger, and the temperature characteristics of piezoelectric and dielectric constants of different piezoelectric ceramic materials are much better than those of barium titanate, which is used as a conversion element for high-temperature sensors. In order to improve the temperature stability and time stability of piezoelectric ceramics, artificial aging treatment should generally be carried out. But natural quartz crystals do not require artificial aging treatment, and their performance is very stable. After artificial aging, piezoelectric ceramics have stable performance at room temperature, but their performance still changes when used in high-temperature environments. To reduce this impact, insulation measures are taken when designing sensors.

4. The influence of humidity

The environmental humidity also has a significant impact on the performance of piezoelectric sensors. IfsensorWorking in a high humidity environment for a long time will reduce its insulation resistance and deteriorate its low-frequency response. In order to achieve this target, necessary measures should be taken: qualified structural design. Assemble the conversion components into a sealed whole, and the relevant parts must be well insulated, strictly cleaned and assembled. The two ends of the cable must be sealed with airtight welding, and if necessary, a fully sealed welding scheme can be used.

5. Cable noise

A regular coaxial cable is composed of multiple stranded wires with polyethylene or polytetrafluoroethylene as the insulation layer, and the external shielding is a braided multi stranded silver plated metal sheath wrapped around the insulation material. When cables are bent or vibrated during work, relative displacement or friction may occur between the shielding sleeve, insulation layer, and cable core, resulting in static charges. Due to the capacitive nature of piezoelectric sensors, this static charge does not quickly dissipate and is directly sent to the amplifier, resulting in cable noise. To reduce this noise. Special low-noise cables can be used, and the cables can be fastened to prevent relative movement.

6. Grounding circuit noise

There are multiple connections in the testing systemMeasuring instrumentIf each instrument and sensor are grounded separately and there is a potential difference at each grounding point, noise will be generated in the measurement system. The effective method to prevent such noise is to ground the entire measurement system at one point. And select the input end of the indicator as the grounding point.