Improved Encoder Accuracy Brings Hidden Benefits

Capacitive rotary encoders such as those from Netzer Precision are known for their low profile, high noise immunity and excellent accuracy. As a result, they are an excellent choice for applications such as camera systems, radar, slip-rings and robotic joints. Often times in these tasks the encoder is used for velocity feedback, ensuring a smooth and steady rotation of an axis. Success not only requires high resolution and accuracy, but also low latency.

To address the needs of these applications Netzer has introduced an Extended Accuracy (EA) option to the DS, VLP and VLX series products. While the EA option does improve static accuracy, it also significantly reduces the amount of noise/error in the position signal. As a result, when velocity is derived from the position information, a much smoother velocity curve appears. For example, consider the two position accuracy plots below for a standard and EA series encoder.

 

The high frequency noise in the top plot (standard encoder) is due to a 4th order noise frequency that occurs on the ‘fine’ cycle of the encoder. In this example the encoder has 32 fine cycles and thus there are 32*4 of this high frequency noise over one rotation. In the lower image the 4th order noise has been significantly reduced in the EA encoder. This results in a much smoother position error curve. When considering that velocity is the derivative (i.e. the slope) of position, it quickly becomes evident that the EA encoder will have a much improved velocity output.

Another significant feature of the EA encoder is that the improvement above occurs not through additional filtering, which would introduce the negative consequence of increased latency. Rather the EA encoder undergoes an additional production step where a unique Look Up Table is generated for the specific encoder. Another benefit is that an EA encoder can be used in place of an existing Netzer encoder with no changes in the communication protocol, making upgrading existing control systems as simple as possible.

To find the right Netzer encoder for your application take a look at our product finder or better yet give  us a call, 856 727 9500 . We would love to learn more about your application and how we can help.

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