Encoders & Resolvers: Choosing The Right Feedback Option

Feedback devices have been increasing in popularity over the last couple of years, as well as in availability on the market. These motion controllers are available in many different types, making the choice of common users for their particular applications difficult. The main doubt is whether to purchase a resolver or an encoder, with both options including many factors that need and should be considered.

Some users consider whether incremental or absolute, others whether optical or magnetic, while some are confused with choosing between the industrial, commercial, extreme or heavy-duty systems. Even with all these questions answered, making the right choice is still difficult. For example, if you are considering revolvers, make sure you know the accuracy, mounting, size, speed and electrical interface. All this is crucial for making the best selection that suits your application.

Encoders-&-Resolvers

On the other hand, if you are considering encoder products, the important factors you must take into account are accuracy, mounting, resolution, connection and output. However, the most important thing when choosing the right feedback device is to know everything related to your application. To help you select the right feedback option, let’s review the incremental encoder products, absolute encoder products and resolvers.

Absolute Encoders

The absolute encoder products are able to detect the exact angle of rotation. These feedback devices use a unique binary pattern which does not repeat itself within the revolution, providing the devices its absolute attributes. Also, the feedback changes when the power is removed from the feedback devices, changing the rotational position. In an optical absolute, the disc rotates between the sensor and LED and light either is transmitted to several sensors or blocked, depending on the pattern of the disc. In other words, this is what provides on/off of each bit in the digital signal from the absolute encoder.

Incremental Encoders

To interpret the position, the incremental encoder products use external electronics. To do so, these electronics count the events that occurred on the device. The outputs for incremental encoder products usually come in a single-square-wave form, but they also come in phased square waves for determining the rotation direction. There are two encoder engine groups: magnetic and optical. Both engines styles have a similar sensor alignment, so they provide output compatibility. When it comes to popularity of speed feedback devices, incremental encoder products are still the primary choice.

Resolvers

Resolvers are very similar to the electro-mechanical devices that convert the mechanical motion into an electronic signal. The main difference is that a resolver is used for transmiting the analog signal instead of the digital. The resolvers are most preferred for maximum duty applications, as they have a simple component similar to electric motors. Time tested and proven, resolvers are the usual choice in servo motors, aerospace and military applications.