B3.2 - Strain Gage and Piezoelectric Based Force Sensors – A Comparison
- SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
- Proceedings SENSOR 2011
- B3 - Mechanical Sensors I
- T. Kleckers - Hottinger Baldwin Messtechnik GmbH, Darmstadt (Germany)
- 257 - 360
Force Sensors play a critical role in mechatronic and test systems, because input quantities are essential to the interaction of mechanical engineering, electronics, and information technology. Measuring forces at high accuracy often is a compulsory requirement in this field. For this purpose, modern sensors based on strain-gage and piezoelectric methods are available.
Strain gage-based force transducers use a loaded member which converts the force to be measured into a mechanical stress. The strain gages are installed at selected points where a defined strain occurs under load; this strain can be measured by strain gages and is converted into a change in resistance. A bridge circuit allows resistance changes to be converted into an output voltage. This output voltage is proportional to the force applied.
Piezoelectric transducers use the piezoelectric effect. Here, monocrystals (e.g. quarz or gallium phosphate) are used. With these materials, charge centers are shifted in specific directions in the crystal; this results in an electric charge that can be detected externally and analyzed using a charge amplifier.
The principle of strain gauge based transducers allows the compensation of temperature effects as well as mechincal influences by using the characteristics of the Wheatstonebridge. More than this mordern strain gauges are nearly drift free so that high precision measurements over years are possible.
Piezoelectric force transducers show advantages in situations where high overload capacities or low dimensions are required. As these trasnducers show a very low diosplacement under load, high stiffness and therefore a high natural frequency is given. This leasd to best dynamic properties. The characteristic of the measurement principles show complimantary advantages which gives both systems the right to exist...