Analysis on The Maximum Reliable Working Temperature of Vibrating Level Switch

Piezoelectric devices are the core elements of vibrating level switches, and piezoelectric ceramics are the most commonly used piezoelectric devices. Generally, the vibration driving and detecting components composed of multiple pieces of piezoelectric ceramics are also called piezoelectric ceramic components. From the structural design of vibrating level switch, the piezoelectric ceramic components should be set closely by the vibrating probe to improve the driving efficiency and working reliability. When the instrument is installed in a specific application, the whole probe must be inserted into the storage tank or pipeline. Therefore, the working reliability of the piezoelectric ceramic component determines the reliable working temperature of the vibrating level switch.

The working reliability of piezoelectric ceramic components is affected by many factors, such as process temperature, environmental humidity, assembly preload stress and the stress of fixed parts. Temperature is the most significant component, because of the structure of semi-stable state domains (non 180 ° domains) in piezoelectric ceramics are easy changed by thermal energy that released in high temperature ambient, and then resulting in depolarization of some domains and aging of electrical properties; especially in the case of sudden temperature change, the sudden accumulation of thermal energy tends to make the domain turn and depolarize the piezoelectric ceramics, and this degradation is irreversible. The dielectric constant is used to measure the performance parameters of piezoelectric ceramics ε，piezoelectric constant D, electromechanical coupling coefficient Kp, quality factor QM, Curie temperature Tc, etc. The Curie temperature Tc determines the maximum temperature at which the piezoelectric ceramic module is able to work reliably in the long-term. Based on the temperature performance curve of piezoelectric ceramics, the maximum temperature at which the piezoelectric ceramic components is able to work reliably and persistently shall not exceed half of its Curie temperature Tc value.

The fixing and assembly design of piezoelectric ceramic components of Jiwei level switch products fully considers the strict high-temperature working environment, and adds a temperature buffer isolation device in the piezoelectric ceramic components. Even if the process temperature changes suddenly, the temperature of the whole components will be stable and with a moderate growth; so as to ensure the overall excellent performance of the instrument.