![]() The motor is simple in construction, reliable.The various benefits of the Stepping Motor are as follows: Small steps angle can be obtained by using slotted pole pieces. The number of phases can vary from two to six. The various step angles like 90, 45, and 15 degrees are common in simple motors. ![]() A standard motor will have a step angle of 1.8 degrees with 200 steps per revolution. Some precision motors can make 1000 steps in one revolution with a step angle of 0.36 degrees. The higher the resolution greater will be the accuracy. The accuracy of positioning of the objects by the motor depends on the resolution. The smaller the step angle, the higher the resolution of the positioning of the stepper motor. The resolution or the step number of a motor is the number of steps it makes in one revolution of the rotor. Some protocols, such as BiSS allow for a delay compensation to improved performance over longer cable runs.The positioning of a motor is decided by the step angle and is expressed in degrees. In the case of SSI, a long cable run and a high clock frequency can disturb the data signal due to propagation delay of the signals over copper wires and it is necessary to reduce the clock frequency or the cable length for the system to work. For example, for the SSI encoder interface protocol, the recommended data transfer rate by cable length is: Cable Length vs. Generally, baud rates decrease as cable length increases. Example Encoder Resolution (Bits)īaud rate is unique for each encoder communication protocol and varies by cable length. A 14-bit encoder, for example, can measure 16,384 discrete positions per one revolution of 360°, which would satisfy the above example. As a result, the resolution is measured in terms of bits N, with the encoder measuring 2 N positions per revolution. The code discs of absolute encoders are patterned to generate a unique digital word for a specific number of angular or linear positions of the load. Next, convert the number of discrete positions required to the next highest bit count. To determine number of discrete positions required (N), first determine the smallest incremental of measurement (I) required within 360 degree rotation:įor example, if you require measuring down to 0.01 degrees, the resulting calculation would be N = 360 / (0.03) = 12,000 discrete positions. Therefore, absolute encoders are not limited by frequency response in relation to total pulses but by the amount of data communication required over a specific sample period, or baud rate. Unlike incremental encoders that are a push only system that output a continuous stream of pulses whenever the shaft is turned, absolute encoders are a call and response system that output a bit or unique word that relates to discrete position only when they are interrogated by the controlling device. Learn more about quadrature encoders and encoding to achieve higher resolutions hereĪbsolute Encoder Resolution (Bits) Calculation Assuming the usage of quadrature encoders with bidirectional output (A and B channels), triggering from the rising and falling edges of the A channel and the B channel will generate four times as many pulses, or 4X encoding. If your encoders standard resolution doesn’t meet your application needs, there is another alternative based on how the signal is decoded through the users drive, PLC or Controller. Max encoder resolution = Operating Frequency x 60 / Max RPMĮxceeding this number will overwork the encoder’s processing capability, which will result in degraded signal output and cumulative error.įor example, if the encoder’s operating frequency is 125kHz and the maximum shaft speed is 1,000 RPM, the encoder ppr calculation for the maximum resolution the encoder supports is 7,500 pulses per revolution (PPR). ![]() Combined with the RPM of the application, the frequency response places a practical upper bound on the resolution that can actually be achieved for a particular system and encoder. Incremental Encoder Resolution (PPR) Calculationįor incremental encoders, the encoder electronics have a maximum frequency response, which limits how rapidly it can generate output pulses.
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