WTMplus 2.0 – Wireless Temperature Measurement

For many applications e.g. in an isolator environment it is virtually impossible to place conventional wired temperature sensors. For this reason, freeze drying cycles with these units are usually conducted without temperature measurement, relying instead on validation runs.

In response to the Process Analytical Technologies (PAT), we have taken a new course and use the WTMplus 2.0 wireless product temperature measurement system for freeze drying. The wireless self-powered sensors are placed manually or automatically when the product vials or dishes are filled and report the corresponding product temperatures to the unit controller during the entire lyophilisation process. The WTMplus 2.0 temperature sensors are operating battery-free.

Working principle:

  • Wireless power transfer to the temperature sensor by an HF signal in the 2.4 GHz frequency band
  • Temporary energy storage in an oscillating quartz crystal
  • Highly accurate temperature-dependent shifting of the quartz crystal resonant frequency
  • Feedback of the frequency shift and temperature determination using sophisticated electronic signal processing

Other features:

  • Falsification of the measured product temperature is avoided by the passive structure without batteries and the extremely low operating power level.
  • Several different sensor frequencies can be used to monitor different sensor positions.
  • Definition of any sensor locations for automatic loading/unloading.
  • Interference-free wireless data transfer worldwide in the 2.4 GHz frequency band
  • Active frequency selection ensures stable signals at every location, even with freeze dryers made entirely from stainless steel.
  • Measurement accuracy ±0.5 K; max. ±1 K
  • Covers the entire process (temperature range –60 °C to +135 °C)
  • Wirelessly transmitted measurement data is available to the LPCplus control software for process monitoring and control

The innovative WTMplus technology is available for all Christ pilot and production freeze dryer with LSCplus an LPCplus/Siemens PLC S7.

Wireless Temperature Measurement WTMplus 2.0

The wireless product temperature measurement system WTMplus 2.0 from Martin Christ makes wireless sensor-based product temperature measurement possible for freeze drying. Automatic identification and localization of the sensors by RFID.