In the fields of motion control and robotics, knowing the position and speed of moving objects is crucial. One of the devices that makes this possible is a quadrature encoder. This article delves into the intricacies of quadrature encoders, explaining their functionality, applications, and selection criteria.
Table of Contents
What is a quadrature encoder?
Quadrature encoder is also called AB dual-channel output optical incremental encoder. The A-phase signal and the B-phase signal are 90 degrees apart. Therefore, we can judge the direction of rotation of the object through the sequence of A phase and B phase. If phase A leads phase B by 90 degrees, the object is rotating forward. If phase B leads phase A by 90 degrees, the object rotates in the opposite direction. Additionally, speed or angle can be calculated by reading the number of A or B pulses. Most quadrature encoders also have a Z phase, also known as the index signal. By reading the value of the Z phase, the number of revolutions of the object can be calculated.
How does a quadrature encoder work?
Learning how the quadrature encoder works, firstly we need to know its structure. We all know that “Structure determines properties, properties determine use”. At its core, a quadrature encoder consists of a rotating disc, photosensitive sensor and output circuitry. The disc, attached to the rotating shaft, has a series of equally spaced slots or markings. As the disc rotates, the sensor detects these markings and produces electrical pulses. Its counterclockwise and clockwise output waveforms are as follows:
How and when to use a quadrature encoder?
In scenarios where precise motion feedback is required, quadrature encoders are invaluable. Some common applications include:
– Robotics: used to determine the position and speed of a robot’s wheels or arms.
– CNC Machine Tools: Know where the tool and workpiece are.
– Conveyor belt system: monitors the speed and position of items on the conveyor belt.
When implementing a quadrature encoder, you must ensure that the system can handle the number of pulses generated, especially at high speeds. Additionally, the encoder should be properly mounted to prevent any misreading due to vibration or misalignment.
How to Achieve higher resolution by quadrature encoders?
The resolution of an encoder refers to the number of pulses it generates per revolution. Higher resolution encoders provide more pulses, which translates into more accurate position feedback.
For higher resolution:
Increase the number of grooves or marks on the disc: more marks means more pulses per revolution.
Using decoding technology: By analyzing the rising and falling edges of both channels, the resolution can effectively be increased by a factor of four.
How to choose a quadrature encoder?
There are several steps to choose an orthogonal encoder:
- Bearing type. Orthogonal encoders are divided into solid shaft type and hollow shaft type. We need to choose the appropriate encoder according to the actual use scenario. The solid shaft encoder needs to be used with a shaft sleeve during installation, and the hollow shaft encoder is more convenient to install. For more differences between them, you can visit this article-3 Big Differences Between Hollow Shaft And Solid Shaft Encoder.
- Determine the outer diameter of the quadrature encoder. The larger the outer diameter, the larger the shaft diameter of the hollow shaft or solid shaft. In addition, the larger the outer diameter, the larger the internal code disk and the higher the resolution.
- Determine the shaft diameter of the encoder. The size of the rotor bearings corresponding to motors with different power sizes will also be different. For details, please see the following bearing sizes of different motors on the market:
| Motor Size | Shaft Diameter (mm) |
|---|---|
|
Small motors |
2mm, 3mm, 4mm, 5mm, 6mm
|
|
Medium motors |
8mm, 10mm, 12mm, 14mm, 16mm |
|
Large motors |
20mm, 25mm, 30mm, 35mm, 40mm |
|
Industrial motors |
45mm, 50mm, 55mm, 60mm, 70mm |
|
Extra-large motors |
80mm, 90mm, 100mm, 120mm, 150mm |
- Determine the resolution. The higher the resolution, the more accurate the measured data will be. Of course, the higher the resolution, the more expensive the encoder will be. The maximum resolution of the Lornentzzi orthogonal encoder can reach 5400 ppr.
- Determine the output. The output of the quadrature encoder can be a 3-phase complementary output, open collector output or voltage output, or a 6-phase push-pull with reverse signal outputs, long-line output. The 6-phase output encoder has stronger anti-interference ability and longer transmission distance.
- Determine the operating voltage. The working voltage of the incremental encoder can be 5VDC or 8-30VDC. In practical applications, it is necessary to consider the working voltage that can be provided to the encoder.
- Encoder outlet method. The cable outlet of Lorentzzi encoder can be side outlet or rear outlet, and the connection method between the wire and the encoder can be aviation plug type or conventional wiring. The aviation plug type encoder has better waterproof performance and a stronger connection.
Conclusion
By knowing the intricacies of quadrature encoders, explaining their functionality, applications, and selection criteria, we ensure that you have got the full knowledge of a quadrature encoder, if you still have questions, please leave a comment below. Our sales team will help you solve the problems.
