Designs and variants
The signals can be interpreted by motor controllers in different ways:
- The direction of rotation can be determined from the phase shift, when the rising edge of a signal first appears.
- Low speeds can be determined by measuring the time between two electrical events, such events being the rising and falling edge on either square wave.
- High speeds can be measured by counting the number of electrical events within a given time period.
The two square waves are 90° out of phase with each other. This phase shift changes sign with the direction of rotation. Fig. 2 shows the general specifications of the signal. The presence of two signals in quadrature enables a processing unit to multiply the number of angular position increments per revolution. For example, using a standard SKF sensor bearing with 64 pulses per revolution and a standard electronic interface that can detect the rising (Low/High) and falling (High/Low) times of each of the two signals, it is possible to obtain 256 electrical events per revolution, which translates to an angular resolution of 1,4° (fig. 2).
SKF motor encoder units provide accurate and reliable signals for effective motor control and are 100% tested for period accuracy, duty cycle and phase shift during manufacture.
- a free cable end with an output signal consisting of two square waves, designation suffix 008A (fig. 3)
- an AMP Superseal™ connector (AMP Nos. 282106-1 and 282404-1), designation suffix 108A (fig. 4)
- filled, under clean conditions, with a high-quality grease (table 1) that is suitable for the most common operating conditions of electric motors
- virtually maintenance-free
For additional information about motor encoder units for extreme operating conditions, contact SKF.