Encoder mounting to find and calculate the zero position
Generally, incremental encoder provides a z phase (zero) signal each circle, and for absolute encoder, each position data value is unique, so there is also a zero position. So, how to determine zero position in using of encoder? Usually there are several ways:
- In the installing encoder, rotate shaft to determine zero position. Usually, incremental encoder and single-turn absolute encoder will be used this method, and hollow shaft encoder also. Disadvantages: difficult to find zero point, low accuracy.
- Similar to the above method, just rotate encoder housing to find zero. This is mainly used for some compact synchro flange (also called servo flange), as shown:
- Powered, move the machine to the position which corresponding to encoder zero position.(In the servo system, servo rotary encoder with U/V/W signal usually use this method).
- Bias calculations, mechanical and encoders do not need to determine zero, depending on the encoder readings and the actual position of the deviation calculation to obtain the offset, the encoder readings after subtracting the offset. Such as reading of the encoder 100, and the actual position 90, calculate the actual position at 0, the encoder readings should be 10, and this “10” is the offset amount, the number of read after the encoder, reducing go to this offset is the position value. Can be repeated several times, the offset correction. For incremental encoders, is to read the original mechanical zero position to a point Z readings, as the offset. High precision encoder, or a large-scale multi-turn absolute encoder, the use of this method.
- Intelligent external zeroing, some intelligent functions with encoder can be supplied externally set functions, such as through the encoder with a key or takeaway software setting function to zero. And we provide intelligent absolute encoder with CALT brand provides an external set line, this line encoder supply short touch of a positive supply, encoder position at this time is pre-determined preset position (preset can be zero, it can be other pre-agreed location).
It should be noted that the absolute encoder zero position further down is encoded cycle maximum, whether it is a single-turn absolute, or multi-turn absolute value, if set to zero, then further down (down, move, inertia overshoot, etc.), it is a sudden jump to the maximum possible data, and for the high number of absolute multi-turn, may overflow the original data set range. In addition, there is an absolute encoder rotation direction issue, set to zero, if the wrong direction, is the biggest jump from 0, and then from large to small. Although some imported with external encoder zero function, but it is recommended not to use this feature.