In mechanical measurement, piezoelectric power sensors and strain gauge sensors dominate, but in specific applications, which principle is more appropriate? Measuring Tape,Metric Tape Measure,Rolling Tape Measure,Metric Tape SHANGQIU CHAOYUE MEASURING TOOLS CO., LTD , https://www.equipmentool.com
Principle and application of piezoelectric power sensor and strain force sensor
In mechanical measurement, piezoelectric power sensors and strain sensors dominate, but in specific applications, which principle is more appropriate?
1. Technical principle The force exerted by the strain sensor is applied to an elastomer. The load will cause slight deformation of the elastomer. The strain gauges mounted on the elastomer will be stretched and the resistance of the strain gauges will change. The four strain gauges form a Wheatstone bridge and the resulting output voltage will be proportional to the applied force.
The piezoelectric sensor uses two crystal plates with an electrode foil mounted between them. When a force is applied, a charge change will be produced which can be obtained by a charge amplifier. The charge will be proportional to the applied force.
2. Which sensor principle is right for your application?
Static monitoring tasks Strain-based sensors have virtually no drift, making them ideal for long-term static monitoring tasks. This is called creep - it is time dependent. But by choosing the right strain gauge, the output signal caused by a constant load changes very little - in many applications this error is negligible.
The piezo power sensor has a drift - about 1 N/min under operating conditions. Since the value remains the same, it will produce a large measurement error when a small force measurement is performed for a long time. Long-term testing is possible when measuring 5000 N, but smaller force drift effects are very large. Therefore, the period of measurement depends on the required accuracy and the magnitude of the measured force.
Dynamic force measurement During the force loading process, the piezoelectric sensor has only a very small deformation - extremely high stiffness. This results in a very high resonant frequency and is ideal for dynamic testing. However, the components on which the sensor is mounted need to be of greater mass and have a greater impact on the overall quality and cutoff frequency of the system. In addition, the bandwidth of the charge amplifier depends on the charge, so the high charge caused by the large force measurement in turn limits the bandwidth.
The strain sensor has a higher cut-off frequency at higher rated forces. The small-range force sensor has a softer elastomer - the resonant frequency is lower. However, when performing small-scale force for rapid testing, the piezoelectric power sensor is the first choice, and for larger forces, the strain-based sensor should be selected.
The amplifier that calibrates the task to the strain sensor can perform a variety of error compensation. This includes temperature compensation for sensitivity and zero, as well as linear and bending moment errors. Therefore, the strain sensor is ideal for high-precision static calibration, and higher repeatability is achieved with the elastomer structure. Therefore, for mechanical calibration, sensors based on the strain principle are the only choice.
High Initial Load During the force application, the charge generated by the piezoelectric sensor can be shorted if needed. The charge amplifier input state can be displayed as 'zero'. Therefore, the input range of the charge amplifier can be unaffected by high initial loads. Therefore, the piezoelectric sensor can maintain high precision under high initial load conditions.
Some strain sensor sensors have an IP68 protection rating in harsh environments. A tightly sealed housing protects sensitive strain gauges. This allows it to be used in harsh environments. Piezoelectric sensor cables can be secured with special protection to ensure their operational safety. (KAB145-3)
High-precision measurement Modern force sensors are highly accurate, with strain sensors measuring only 200 ppm. Piezoelectric sensors have a slightly higher linearity error, typically 0.5% of full scale. The limitation is mainly due to drift, which allows for higher accuracy by calibrating the entire range.
The space-limited piezoelectric sensor is very compact, for example the CLP series is only 4 mm high. It is therefore ideal for integration into existing systems. Although its accuracy is relatively low, piezoelectric sensors should be preferred in applications where space is at a premium.
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