Measuring Accuracy

The accuracy of linear measurement is mainly determined by:The quality of the graduation The quality of the scanning process The quality of the signal processing electronicsThe error from the scale guideway relative to the scanning unitA distinction is made between position error over relatively large paths of traverse—for example the entire measuring range—and that within one signal period. • ••• Position error over measuring length ±a . The accuracy of exposed linear encoders is specifi ed in accuracy grades, which are defi ned as follows: With exposed linear encoders, the above defi nition of the accuracy grade applies only to the scale. It is then called the scale accuracy. The extreme values of the total error Position error within one signal period Signal period of scanning signalsTypical position error F of a position lie—with reference to their mean value—over any max. one-meter section of the measuring length within the accuracy grade u within one signal periodLIP 3x2 The position error within one signal period is determined by the quality of scanning and the signal period of the encoder. At any position over the entire measuring length of an exposed HEIDENHAIN linear encoders it does not exceed approx. ±1% of the signal period. The smaller the signal period, the smaller the position error within one signal period. It is of critical importance both for accuracy of a positioning movement as well as for velocity control during the slow, even traverse of an axis. 0.128 µm0.001 µm LIP 4x1 2 µm0.02 µm 4 µm0.04 µm LIP 5x1LIF PP
Position error LIDA 4xxLIDA 5xx 20 µm0.2 µm LIDA 2xx 200 µm2 µm Position Position error u within one signal period
Position error Signal period360 °elec.
Signal level

10