Incremental gratings consist of periodic lines. The reading of position information requires a reference point, and the position of the mobile platform is calculated by comparing with the reference point.
Since the absolute reference point must be used to determine the position value, one or more reference points are also engraved on the incremental grating scale. The position value determined by the reference point can be accurate to one signal period, that is, the resolution. In most cases, this type of scale is used because it is cheaper than an absolute scale.
However, in terms of speed and accuracy, the maximum scanning speed of the incremental grating depends on the maximum input frequency (MHz) of the receiving electronics and the required resolution. However, since the maximum frequency of the receiving electronics is fixed, increasing the resolution will result in a corresponding decrease in maximum speed and vice versa.
Absolute grating, the absolute position information comes from the grating code disc, which consists of a series of absolute codes engraved on the ruler. Therefore, when the encoder is powered on, the position value can be obtained immediately, and can be read by the subsequent signal circuit at any time, without moving the axis, and performing the reference point return operation.
Because homing takes time, homing cycles can become complex and time-consuming if the machine has multiple axes. In this case, it is advantageous to use an absolute scale.
Also, the absolute encoder will not be affected by the maximum input frequency of the electronic device, ensuring high-speed and high-resolution operation. This is because the location is determined on demand and using serial communication. The most typical application of absolute encoders is the placement machine in the surface mount technology (SMT) industry, where simultaneously improving positioning speed and accuracy is a permanent goal.
Post time: Jan-06-2023
