In this video we review the basic definitions of resolution, accuracy, and repeatability.
These parameters fundamentally impact the complexity, cost, and development time of a motion system. Understanding them can help you meet your requirements for performance, without adding unnecessary cost and time to market.
- First, we discuss position resolution, often called precision, and the difference between open-loop and closed-loop resolution.
- Second, we mention accuracy. In practice, this is the least important of the three terms. This is because calibration can improve accuracy up to the limits of the system’s resolution and repeatability.
- Finally, we demonstrate the difference between uni-directional and bi-directional repeatability and explain why it matters.
Read the article
Read Understanding Resolution, Accuracy, and Repeatability in Micromotion Systems by New Scale’s David Henderson, at Photonics.com. Here are key figures from the article:
Figure 1. Resolution defines the smallest increment of motion that a system can achieve, which, on the dartboard, translates to how tightly darts can be grouped. Accuracy is illustrated by how close a system’s actual position is to a target position — in this case, the bull’s-eye. Repeatability (often called precision) denotes the level of variation in actual positions after several attempts are made to achieve the target position.
Figure 2. Accuracy variance in motion control systems is often repeatable and can therefore be mapped, stored in memory, and corrected for by command offsets. As long as the variance is repeatable, accuracy can be improved. Building on the metaphor of a dartboard, a person with a repeatable throw can improve their accuracy by adjusting their aim down and to the right.
Figure 3. Bidirectional and unidirectional repeatability for a New Scale Technologies M3-F Focus Module with a piezoelectric motor and closed-loop control.
- Read deeper: open-loop vs. closed-loop positioning
- Learn more about what’s inside an M3 module: M3 Motion Modules integrate a motor, mechanics, and drive electronics. They have small size with with high resolution and repeatability. When embedded into precision instruments, they reduce development time for instrument designers.
- Browse the linear stages, actuators and rotary stages in the M3 Module line.