Temperature and pressure monitoring of a whipped cream device

This paper presents a prototype of a wireless temperature and/or pressure sensor designed for operation inside a thermal insulating double-walled steel vessel. This is achieved by means of a passive (semi-active) radio frequency identification (RFID) transponder which obtains the energy required for its operation from a super low frequency (SLF) external field. The measured temperature and/or pressure data is encoded in the frequency domain (very low frequency range) by means of a digital inverter oscillator and transmitted to a reader coil outside the vessel by load modulation of the power-supplying external field. In previous work, wireless powering and data transmission of a capacitive fill level measurement through a single steel wall had been successfully realized. As the feasibility of data transmission through two distant steel walls has been shown, passive sensors for multiple process measurands (e.g. temperature, pressure and/or fill level) in hermetically sealed vessels can be implemented using this principle.