Shrinking sensor means faster, more accurate results

A novel sensor that has miniaturised optical emission spectrometers could make the analysis of gold and steel more precise and less time consuming. Researchers from the Fraunhofer Institute for Microelectronic Circuits and Systems have developed a sensor that shrinks the size of the spectrometer optics. The new sensor can deliver more precise results in half the time – particularly beneficial in the automotive industry when performing quality assurance. “Whereas earlier high-resolution spectrometers were the size of a washing machine, those built using our sensor will be no bigger than a microwave oven,” said Werner Brockherde, IMS department head. Emission spectrometers analyse materials on the basis of their emitted light spectrum. To analyse steel, for example, it has to generate sparks at regular intervals, which knock atoms out of the material, resulting in a plasma that emits multi-coloured light. The plasma light is split into two beam channels and broken down into several wavebands which are analysed separately. In the first, light-sensitive electronic components known as CCD line sensors record the entire spectrum of the sample, revealing the nature and concentration of particles suspended in the plasma. From this, it is possible to derive the composition of the steel sample and experts refer to this as a space-resolved measurement. The second beam channel produces time-resolved measurements of individual spectral lines, adjusted so that the instrument can distinguish between light emitted by the plasma and that emitted by the sparks. The new system allows such measurements to be taken in parallel, meaning only one beam channel and a single optical unit. The photo-detector multiplies the dynamic range by 100, giving a much faster spectrometer, capable of measuring signals in the microvolt range at the same time as signals measuring around 100 millivolts. Until now, this required several measurement cycles. The high dynamic range also offers other advantages, says Brockherde: “Because we can now measure the entire spectrum with a single series of pulses, the measurement accuracy is also higher.