Understanding Smart Sensors - Nomads.usp

Mechatronics and Sensing Systems 261power portion of the system. For a power node to be added to an existing system,it must have the appropriate protocol to operate on the system.11.3.4 MEMS RelaysElectrostatic and electromagnetic MEMS relays have been produced usingmicromachining processes. Magnetically actuated relays can achieve largerforces and a greater air gap between contacts than electrostatic designs [5]. Thelarger gap provides greater isolation for applications at higher voltages.Micromachining processes used to produce the microrelay include surfacemicromachining and polyimide-mold electroplating techniques. The electromagneticrelays operate below 5V, so they can be directly interfaced to anMCU or a DSP. The relays have operated 850,000 cycles without failing. Thecombination of this adaptation of mechanical technology with micromachiningand MCU and DSP technology should provide some useful mechatronicsolutions.11.4 Sensing ArraysMore than one sensor is frequently required to provide sufficient informationfor a control system. R&D efforts are progressing in several areas to integratethe sensors ultimately on the same silicon wafer with signal conditioning, computationalcapabilities, and possibly even actuation. In the short term, a singlepackagesolution is proving to be an improvement over prior units. The sensingarrays can include a number of sensors for different measurands, for example,pressure, flow, temperature, and vibration. Multiple sensors of a given type canbe used to increase the range, provide redundancy, or capture information atdifferent spatial points. Also, multiple sensors of a given type, with minormodifications, can be used to measure different species in chemical sensingapplications.11.4.1 Multiple Sensing DevicesImproving the performance of sensors can be accomplished by simultaneouslyfabricating several sensors on the same silicon substrate or mounting severalsensors in a hybrid package. One example of the monolithic approach is thesurface micromachined pressure sensor developed by the Fraunhofer Instituteof Microelectronic Circuits and Systems [6]. Surface micromachining wascombined with CMOS processing to achieve a monolithic smart sensor. Asingle absolute capacitive surface micromachined pressure sensor with a