The most important technology − utilized in numerous Kistler sensor solutions − is based on what is known as the piezoelectric effect, which makes a very wide measuring range possible. But we also make selective use of other measuring principles.
- Piezoelectric technology
The property of certain crystals to emit a proportional electric change if they are subjected to a mechanical load (such as a force acting on the crystal) is known as the piezoelectric effect. This effect is used in sensor technology to accurately determine an acting force, pressure or acceleration by measuring the charge. Sensors that utilize this effect are ideal for measuring tasks with exceptionally extreme requirements as regards miniaturization, temperature range and dynamics. Thanks to their rigidity, piezoelectric sensors can measure the highest frequencies and even after many years of use, their sensitivity is unimpaired.
- Piezoresistive technology
Kistler's piezoresistive sensors are mainly used to measure pressure in gases, fluids and viscous media, and for static measurements. In the piezoresistive measuring technique, an elastic diaphragm of monocrystalline silicon is bent under pressure. A Wheatstone measuring bridge made of semiconducting resistor elements is diffused into the diaphragm and is connected to a power supply. As this bridge is unbalanced in proportion to the pressure applied, it produces a voltage that is also proportional to this pressure.
- Strain gage technology (also known by its German initials, DMS)
The operating principle of strain gage technology is based on the physical effect of the electrical resistance of a metal wire that changes in proportion to the change in its length due to stretching or compression under an applied force. This change in resistance can be used as an indicator of the applied force. It allows measurement of tension and compression without any measuring element preload. Kistler uses special strain gage solutions of this sort for applications such as wheel force transducers.
- Other technologies
Capacitive sensors are mainly used to measure acceleration. The operating principle of a capacitive accelerometer is based on the change in capacitance of a silicon measuring element due to an imposed acceleration. Optical sensors measure speed, distance, slip angle and other safety-relevant parameters without contact. The results are used to analyze the dynamics of a test vehicle. The Correvit technology used for this purpose has the advantage of working perfectly regardless of the test track surface.