Encoder accuracy

Encoders measure angles by converting physical parameters into digital signals. As with any measuring device, errors are inevitable due to various influencing factors. This article focuses on encoder accuracy.

Encoder accuracy

First, a measurement process involves at least two components: the measuring device and the measured object. The factors affecting the final result include:

• Position: the relative physical position between the two devices
• Environment: the surrounding conditions where the process takes place

The above two factors are fundamental to any measurement process and can directly affect measurement accuracy.

Encoder accuracy

As an angular measuring device, the encoder has two accuracy parameters:
• Absolute positioning accuracy
• Repeatability

Absolute positioning accuracy is the difference between the measured value and the true position. For example, if two encoders measure 30.08˚ and 29.98˚ for a true angle of 30˚, the latter is more accurate. If the error stays within 0.05˚ over 360˚, the absolute accuracy is 0.05˚.

Repeatability refers to the difference in the encoder’s readings when it returns to the same position. For example, if an object points to 30˚ and the encoder reads 30.02˚, then after moving away and returning it reads 30.01˚, the repeatability error is 0.01˚. Similarly, if the return error at every position within the full 360˚ range is within 0.01˚, then the encoder's repeatability is considered to be 0.01˚.

It can be seen that,Absolute positioning accuracy is state-based, with its reference coordinate being the true physical position; repeatability is process-based, with its reference coordinate being the previous measurement at that position.

Positional factor

Each encoder measurement principle includes a stationary sensing part and a rotating measured part. The measured part connects to the target object, and the sensing part to the housing — this setup introduces two types of errors:

• Rotor mounting misalignment
• Stator misalignment

Rotor and stator misalignments, together with motion-induced vibration of the measured object, affect their relative positioning and thus reduce measurement accuracy.

Environmental factors

Due to differences in measurement principles, each type is affected differently by environmental factors.

• Temperature: A common challenge for all principles, with corresponding solutions and algorithms developed for each.
• Solid particles (dust, debris): Optical encoders are particularly sensitive because such particles can obstruct the light passing through the code disk, leading to signal loss or data errors. The solution is a fully sealed enclosure.
• Humidity: Capacitive encoders are more sensitive to humidity, which affects capacitance and thus impacts the acquired data. Solution: Sealed isolation.
• Liquids: Optical and capacitive encoders are more sensitive to liquids, which can affect light transmission in optical encoders and dielectric properties in capacitive encoders. Solution: Sealed housing or potting.
• Magnetic interference: Magnetic encoders are more sensitive, as external magnetic fields can interfere with the magnetic ring’s field. Solution: JG Tech's magnetic shielding cover.

Magnetic Encoder

Among all principles, magnetic encoders offer the strongest resistance to environmental interference and can operate reliably in extremely harsh conditions.

KingKong Technology’s patented magnetic encoders offer high-precision mounting and strong magnetic shielding to ensure measurement accuracy. Each unit is individually calibrated to eliminate magnetic inconsistencies, ensuring reliable data output.