The paper presents the principles of construction and functioning of compound piezoelectric transformer sensors (PTS) for bulk materials. The studied PTS are suitable for high temperature, chemical, and mechanical applications. The sensing elements (SE) are piezoelectric composite transformers (PCT) with agreed dimensions. Depending on the construction and the intended use of the transducer, the PE can be an oscillating system with one, two, or more degrees of freedom or a system with distributed parameters. Therefore, it is possible to use these types of devices as alarm devices and perform continuous level control of bulk materials in containers. Excitation of mechanical vibrations in the sensitive element of the sensor and the formation of output signals can be carried out by the schemes with one or two PET. For the first variant, the ratio of output voltages taken from one PCT at normal synchronization frequencies (NSF) of in-phase and antiphase oscillations in the system is used as a transducer output signal. The second variant uses output voltages from two PTS at one of the NSF. Deployment of the appropriate scheme and the method of forming the sensor output signal allows increasing the metrological and operational characteristics of measuring devices of such types to extend the measurement range and operation conditions. The sensitivity mechanism of the sensor is described, the results of simulation of sensor operation are presented, and recommendations on the development and design of measuring devices of this type are worked out.