Robust sensor elements for temperature measuring devices

Corona is a real test of endurance for our health systems. Countries around the world are scrambling to find free intensive care beds, lung ventilators and enough vaccine. But not only the quantities, also the quality must be right. Temperature sensor elements from Heraeus Nexensos ensure that the cold chain is maintained during vaccine transport and that lung machines stabilize patients.

Heraeus Nexensos platinum sensors

In order to provide the best possible medical care to patients suffering from Covid-19, hospitals around the world are upgrading. They are procuring additional ventilators and increasing the number of beds in intensive care units. Before the Corona crisis, there were about 22,000 intensive care beds with ventilator capability in Germany nationwide. By December 2020, the number could be increased to over 28,000, the German Hospital Association reported. In addition, there is a reserve of up to 12,000 more beds that can be put into operation if needed. Operating the lung machines, however, is not so easy: for ventilators to work, the air temperature must be measured and constantly monitored. The oxygen-enriched breathing gas must be close to the patient's body temperature and be able to be adjusted if it is too humid or too dry.

An even greater challenge is vaccine procurement. Finally produced and licensed, it is now important that the vaccine reaches doctors and vaccination centers safely. The cold chain must be maintained at all costs - and at extreme temperatures. The vaccine from Moderna, for example, has to be transported at minus 20 degrees, while the vaccine from Biontech and Pfizer even needs sub-zero temperatures of around minus 70 degrees in order to be effective.

Our contribution: Platinum resistors for temperature sensors

In order to monitor the cold chain, pharmaceutical companies equip their vaccine deliveries with so-called data loggers that constantly document the temperature. If the temperature is significantly higher or lower, the device's sensor notices this by measuring the resistance. If the temperature rises, the resistance increases. Manufacturers also install up to three temperature sensors in ventilators to stabilize patients during the ventilation process. But while low temperatures are just right for the vaccine, sensors – depending on what they are made of – sooner or later reach their limits. They are in danger of becoming inaccurate. The nature of the sensors is therefore a critical factor for success.

Heraeus Nexensos platinum temperature sensor elements
M-Series platinum temperature sensors are suitable for temperatures from -70 degrees to +500 degrees and are characterised by long-term stability, high accuracy over a wide temperature range and compatibility

The  Heraeus Nexensos business unit manufactures platinum sensor elements specially developed for different temperatures. The substrates coated with a platinum structure can be used to manufacture  cryosensors (C-type) that are ideally suited for a broad temperature spectrum from minus 196 degrees to plus 150 degrees Celsius. In contrast to sensor elements made of ceramic materials, platinum thin-film sensor elements are mechanically very robust and function reliably and precisely even at minus 70 degrees. For this purpose, the elements are typically extended with cables and installed in a stainless-steel tube. This protects them and allows them to be easily connected to the electronics of a data logger or measuring device.

However, the platinum elements are not only suitable for low temperatures, but also for ventilators. Here, the  M-type is often chosen for "medium" temperatures : These have the advantage of being particularly durable. The sensor elements are also standardized. In case of a defect, the sensor can be replaced quickly and easily without having to adapt the software or electronics. The sensor elements are the heart of the temperature sensors and data loggers – and thus also an essential component of good medical care during the Corona pandemic.