The characterization of length, distance and position sensors/transducers is based on the measurements of the linearity and deviation of their output signals and displays etc. Laser interferometers are usually applied to the precise measurements of length sensors and transducers. This is an expensive solution for engineering applications. A cost favourable measuring and testing system is developed by applying a self-correction measuring method. The following figure shows a scheme of self-corrected measuring and testing system.

1: Moveable table     2: Reference transducer     3: Reference detector    
4: Measuring transducer     5: Measuring detector

This system consists of a reference channel and a measuring channel. A difference measurement is realized by using the both channels so that the influences from temperature change can be compensated if the material of reference transducer is the same of the measuring transducer.

In order to compensate the measuring deviation, the measuring and testing system is calibrated in advance with the use of a calibratoion transducer. The calibration data e_m (X) are stored as correction matrix in the PC-System. The measuring result e_x(X) can automatically be corrected according to the correction matrix.

Therefore, the accuracy of the self-corrected measuring and testing system depends on the tolerance of calibration transducer. If the calibration transducer is calibrated with a laser interferometer in advance, its deviation can be included in the correction matrix. Thus, the deviation of the calibration transducer can also compensated by the correction algorithm. The accuracy of this measuring and testing system is comparable with that of the laser interferometer used for calibrating the calibration transducer. This measurimg and testing system can be operated under normal surrounding conditions.