Environmental Measurement Applications

Environmental conditions have a considerable influence on our health and well-being. With the aid of physical and chemical sensors, it is possible to measure environmental properties such as temperature, pressure and moisture, as well as the concentration of gases and the composition of fluids. However, optimal sensor functionality can only be achieved by way of application-specific integrated circuits (ASIC) designed for the best possible signal processing. The ASICs developed by us can optimize the performance of sensor systems while simultaneously reducing costs and dimensions.

With our expertise in circuit design, we can support our customers in the development of sensor systems for

• the measurement of air quality
  
• the measurement of gas concentration
  
• the detection of specific molecules in liquids.

In cooperation with our partners, we have developed read-out electronics for a number of types of chemical sensors used for the measurement of liquids and gases.

• MOX (metal-oxide sensors)
• MIPs (molecular imprinted polymers)
• MOFs (metal-organic frameworks)
• Micro-pellistors (pellet resistors)

ASICs for gas sensors

Metal-oxide gas sensors are ideally suited for the measurement of air quality in both building automation applications as well as in ventilation control systems for vehicles. In order to enhance the measuring accuracy and long-term stability of miniaturized metal-oxide gas sensors, Fraunhofer IIS has developed an integrated read-out electronic in the form of an ASIC that covers an exceptionally broad measuring range, while simultaneously enabling temperature-controlled functionality. Furthermore, this ASIC chip can be used in combination with a pellistor to safeguard against dangers posed by combustible gases.

ASICs for electro-chemical sensors

In foodstuff monitoring the detection of contaminants and impurities in liquids is of vital importance. By using what are known as molecularly imprinted polymers (MIPs), impurities can even be detected in the most minute concentrations. An MIP consists of a gold electrode that has been coated with molecularly imprinted polymers for a corresponding target substance. The polymers then form a structure in which the target molecules are imprinted like plaster-cast footprints. When these molecules come into contact with the surface they bind together and, in so doing, alter the electrical capacity of the electrode. As a result, the sensor only reacts with the targeted substance and nothing else.

These MIPs are connected to a high-precision, capacitive evaluation circuit that provides a digital output signal. The major advantage of this method lies in the high selectivity of the sensor material combined with its low-cost production. This measurement principle can also be adopted for the detection of drugs in wastewater. In order to better enable the selective detection of trace substances in liquids, the Fraunhofer IIS, in cooperation with their partners CapSenze and the University of Ghent, developed the entire sensor system consisting of MIPs, transducer and ASICs.