We develop sensor material to effectively transform mechanical force or torque into an electrical resistance. A new type of thin films containing nickel and carbon has a significantly higher output and is thus very advantageous. But so far, the electrical resistance lacks stability. We therefore investigate how to stabilize the material and show that the partial replacement of nickel by the element chromium solves the problem. The optimized sensor films are now suitable for widespread use.

We developed a smart in-cylinder pressure sensor for closed-loop combustion control. The sensor concept is based on a robust and reliable steel membrane equipped with highly strain-sensitive and temperature-stable thin films. The sensor system is complemented by a smart electronics allowing real-time data processing for calculation of different combustion parameters. The data are utilized to control the igniting timing of a spark plug for efficient operation of a combustion engine.

NiCr-carbon thin-film strain gauges offer the outstanding characteristic of a very high strain sensitivity. This can be very advantageous for many high-precision mechanical sensors like load cells. A downside of sensors based on these NiCr-carbon strain gauges is a rather large creep error, meaning reversible signal deviations at a constant load. We present two applicable methods for adjustment of the creep error: a modification of the film composition and a modification of the strain transfer.

This paper introduces a new method to drastically reduce the anisotropic strain sensitivity of granular thin film strain gauges. As a result, these improved strain gauges produce a much higher sensor signal when used for force transducers with biaxial strain fields. This gauge type is also more advantageous for uniaxial stress measurements. The method is based on the creation of a certain topographic structure of the strain gauges; in our case, this was realized by a picosecond laser system.

The basis of our work presented in this paper stems from the research on new materials, especially temperature-stable thin films that transform strain into a resistance change very effectively, allowing higher sensitivity and higher operating temperatures. Different sensor concepts for time-resolved cylinder pressure monitoring of combustion engines are realized and evaluated. Reliable sensors with a minimum of internal components are provided.