Precision, resolution, repeatability and nonlinear error are important technical indicators of the main shaft encoder, and we will focus on these technical indicators in this paper.
Accuracy is the approximation between the measured value and the real value. Without comparison with the standard, the accuracy can't be discussed. Precision and influence by the sensor's basic error limit changes (such as temperature, humidity, power fluctuations, frequency change, etc.) caused by the change quantity limit. The accuracy of the main shaft encoder determines the total measurement error of the system. The measurement error usually involves a variety of factors, such as non-linearity, delay, or cross sensitivity of the working environment (such as temperature and vibration). The error of the system can be partially or completely corrected by linearization. The accuracy of the encoder is usually expressed in an Angle or a distance. If the corresponding number of steps is 2, the accuracy is usually expressed in the form of "digit". Note: "number" is the exponent of 2.
Accuracy, for example: 14 bits = 120 seconds
Resolution is the minimum scale can be displayed or measuring unit, the resolution refers to the main shaft encoder to position changes (step), its size depends on the use of sensing elements. In general, the resolution of the encoder is improved by subdivision, but segmentation increases the signal noise. The resolution of rotary encoder usually axis rotation with a week signal output change (steps), or, per mm distance between the corresponding linear encoder signal output change (steps). If the number of steps is 2, the resolution is usually expressed as "bit". Resolution is a very important factor for speed (or acceleration) computation. Resolution, for example: 262144 steps = 18 bit = 5 kermes
Repeatability is the ability to reproduce the same result in an external state. In some applications, repeatability may be more important than accuracy. This is because if the system is repeatable, the error can be eliminated by compensation. The repeatability of the main shaft encoder is the maximum deviation of the encoder in a given position measuring five times. In general, repeatability indicates the random variable value of the position signal over time. These changes are usually caused by the signal noise of the encoder. Signal processing reduces noise, but this also reduces the bandwidth that the encoder outputs. Repeatable, for example: + / -7.2 seconds
Main shaft encoder input and output (measurement, results) as vertical and horizontal axis of a rectangular coordinate system respectively, choose suitable coordinate axis, and will be the ideal input and output into the corresponding point coordinates, can get a ideal relationship between input and output curve. The actual input output corresponds to the coordinates, and the actual input output relation curve can be obtained. Ideally, the two curves should overlap, which is actually impossible, and the distance between the two curves is the error. If the curve shape completely consistent, but not overlap, such as a curve is equivalent to another translation or linear slope the same, then the error is linear, otherwise the error is nonlinear.
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