Guide to Incremental Encoder Technology

An incremental encoder helps you track movement. It changes motion into electrical signals. You see it in robots and CNC machines. It is also in medical devices. These devices need to control speed and direction very well. Incremental encoders are different from absolute encoders. They do not keep track of position if the power goes out. More factories and smart machines use them now. This is because they need better ways to control movement.

You might use an incremental encoder if you are an engineer. Technicians and machine operators also use them.

Key Takeaways

• Incremental encoders change movement into electrical pulses. These pulses help measure speed, distance, and direction. They do not remember position after power is lost.

• There are rotary and linear types of encoders. Signals A and B show movement and direction. The Z signal marks a reference point for re-homing.

• You must pick the right encoder for your needs. Think about your motion type and where you will use it. Also, check what resolution you need and if the signals match your system. This helps you get good and correct feedback.

• Incremental encoders work in many machines. They are good when you want low cost and simple design. But, you must re-home them after power loss. Absolute encoders do not need this step.

• Encoders need good protection to work well. High IP ratings and noise-resistant outputs help them last in hard industrial places.

What Is an Incremental Encoder?

Basic Function

You use an incremental encoder to turn movement into electrical pulses. This device helps you measure how far something moves, how fast it goes, and which way it turns. It does not tell you the exact position at all times. Instead, it shows you changes from a starting point. You need extra electronics to count these changes and keep track of where you are.

An incremental encoder often has a disc or strip with special patterns. When you move the shaft or slide the strip, the pattern passes between a light source and a sensor. The sensor turns the light on and off as the pattern moves. Each time the light switches, the sensor creates a pulse. The number of pulses matches how much you move the shaft or strip.

You can find two main types of incremental encoders:

• The rotary type measures turning or spinning. It uses a round disc with patterns. You see this type in motors, robots, and cameras.

• The linear type measures straight-line movement. It uses a strip or scale with markings. You find this type in CNC machines, 3D printers, and laser cutters.

Tip: The rotary type works best for spinning parts. The linear type fits machines that move in straight lines.

Output Signals

Incremental encoder signals help you know both speed and direction. The encoder gives you two main output signals, called A and B. These signals look like square waves. They are always 90 degrees out of phase. This means one signal leads or lags the other, depending on which way you move.

You can use these signals in the following way:

1. Count the number of pulses from channel A or B. This tells you how far you moved.

2. Check which signal comes first. If A leads B, you move in one direction. If B leads A, you move the other way.

3. Use the Z signal (also called the index). This signal gives you one pulse for every full turn or full length. It helps you find a starting point.

Here is a table to show how the signals work:

The output signals from incremental encoders can use different voltage levels. Some use TTL (5 V), while others use HTL (8-30 V). You may see open-collector, push-pull, or line driver outputs. Each type fits different needs for speed, distance, and noise protection.

You can use incremental encoder signals in both rotary type and linear type devices. The rotary type gives you pulses for each turn. The linear type gives you pulses for each step along a straight path. Both types help you control machines with high accuracy.

How Incremental Encoders Work

Pulse Generation

When you use an incremental encoder, you see how it turns movement into electrical pulses. Inside, a disk or strip has a pattern of opaque and clear lines. As the disk spins or the strip moves, a sensor reads these lines. In optical types, a light beam shines through the disk. The sensor detects when the light gets blocked or passes through. Each time the pattern changes, the sensor creates a digital pulse. Magnetic types use a magnet and sensor to do the same job.

Each pulse matches a small step of movement. If you turn the shaft a little, you get one pulse. If you turn it more, you get more pulses. These pulses go to a counter or controller. The controller adds up the pulses to track how far you moved. The number of pulses per revolution (PPR) tells you the smallest step you can measure. Higher PPR means you can see smaller changes in position. For example, if your encoder has 1000 PPR, you get 1000 pulses for one full turn. This gives you fine control over speed and position.

Note: Quadrature encoding lets you count not just the pulses, but also the rising and falling edges. This can multiply your resolution by four, giving you even more detail.

Channels A, B, Z

Incremental encoders use three main channels to send information: A, B, and Z. Each channel has a special job.

Channels A and B both send out square wave signals. These signals are always 90 degrees out of phase. This means one signal leads or lags the other. You can tell which way the shaft turns by checking which channel comes first. If A leads B, you turn one way. If B leads A, you turn the other way. This is called quadrature encoding.

The Z channel, also called the index, sends one pulse for every full turn. This pulse always happens at the same spot on the disk. You use this pulse to set a home or zero position. When you start your machine, you can spin the shaft until you see the Z pulse. Then you know you are at the exact starting point. This makes your system more reliable and repeatable.

Tip: The Z channel helps you avoid errors after power loss. You can always find your home position again.

Signal Processing

You need to process the signals from your incremental encoder to get useful data. Most systems use quadrature decoding. This method looks at both A and B channels. It counts every edge—rising and falling—on both signals. This gives you four counts for every pulse, making your position tracking much finer.

Some encoders use digital square wave signals. These are easy for controllers to read. Others use sine-cosine signals. These are smooth, analog waves. Sine-cosine encoders let you use interpolation. You can split each cycle into thousands of steps. This gives you even higher resolution, which helps in servo motor control and high-precision tasks.

Noise can affect your signals, especially in busy factories. Many encoders use differential outputs, like A- and B-, to fight noise. These outputs send two signals for each channel. The controller looks at the difference between them. This helps block out unwanted electrical noise and keeps your data clean.

Note: Both digital and sine-cosine encoders lose position if you cut the power. You must re-home the system using the Z channel when you restart.

Incremental Encoder Specifications

Resolution (PPR)

Resolution tells you how small a movement the encoder can see. This is called pulses per revolution, or PPR. PPR means how many electrical pulses you get for one full turn. Most industrial encoders give you hundreds or thousands of PPR. Some optical encoders use special tricks to get up to 100,000 PPR. The Moiré effect is one way to do this. If you use 4X decoding, you can get even smaller steps. For example, you might get 36,000 PPR. This means you can measure tiny changes, like 0.01 degrees.

Typical PPR ranges:

• Standard optical encoders: up to 200 PPR

• Moiré effect or advanced types: up to 100,000 PPR

• Most industrial uses: a few hundred to tens of thousands PPR

High-resolution incremental encoders help you control machines that need very fine movements. In jobs like making computer chips, you can reach very tiny measurements. High resolution lets you see small changes and fix your system right away.

Output Types

You can pick from different output types when you choose an encoder. Each type works best for certain needs.

Tip: If your factory is noisy, use a differential line driver for better signals.

Environmental Ratings

You should check the environmental ratings to make sure your encoder can handle tough places. The IP rating shows how well it keeps out dust and water.

Some encoders have strong cases made from aluminum or stainless steel. Some have sealed bearings and work in very hot or cold places. If you need more safety, use special covers or flexible shafts to keep the encoder safe from chemicals or water.

Note: Always check the incremental encoder's IP rating and case material before you install it.

Types of Incremental Encoders

There are different types of incremental encoders. Each type works best for certain jobs. Knowing the main types helps you choose the right one.

Incremental Rotary Encoder

An incremental rotary encoder checks how much a shaft turns. You can find these in motors, robots, and conveyor belts. When the shaft turns, it sends out pulses. You count the pulses to know speed or distance. Some rotary encoders use a disc with lines. Others use magnets instead. These encoders give quick feedback. This helps you control machines right away.

Tip: Pick an incremental rotary encoder if you need to measure turning or control how fast a motor spins.

Linear Incremental Encoders

Linear incremental encoders measure straight movement. You see them in CNC machines and 3D printers. They use a strip or scale, not a disc. When the strip moves, the encoder sends pulses. You can see how far a part moves. These encoders help you make accurate cuts or prints.

Linear incremental encoders are good for:

• Moving a cutting head to the right spot

• Measuring how far something travels

• Making sure parts line up

Optical and Magnetic Types

You can pick an incremental optical encoder or a magnetic encoder. Each one has special features.

An incremental optical encoder uses light to read patterns. It gives very fine steps and high accuracy. It works best in clean places where you need exact control. An incremental magnetic encoder uses magnets and sensors. It works well with dust, dirt, and shaking. You can use it outside or in tough factories. Magnetic types cost less, so you save money if you need many.

Note: When you choose an incremental encoder, think about where you will use it and how exact you need it to be. Both rotary and linear encoders come as optical or magnetic types.

Applications of Incremental Encoders

Industrial Uses

Incremental encoders are used in many tough places. You find them in steel mills and mining sites. They also work in food plants and road building. These places can be dirty and very hot or cold. There is often dust, water, and strong shaking. Encoders must keep working even if power is not steady. They also work when there is a lot of electrical noise.

• In mining and oil drilling, machines wear out fast. Encoders help these machines work well.

• In paper mills and factories, machines move quickly. Encoders help control them with care.

• Some encoders are made for dangerous places. You may need explosion-proof or safe models.

• You can pick designs that are easy to put in and fix.

Tip: If you ask, "where are incremental encoders used," think about any place that needs to know speed and distance in hard conditions.

Servo Motor Feedback

Incremental encoders help servo motors work better. They are put right on the motor shaft. Many use a hollow shaft design. The encoder sends signals to a controller. The controller uses these signals to check speed and position. This is called closed-loop control.

• You see this in packaging, conveyor belts, and labeling machines.

• The encoder checks how far and how fast the motor turns.

• It helps the controller make quick changes for smooth moves.

• You get very good accuracy, even at high speeds.

You need incremental encoders to check motor speed. They help machines run safely and without problems. If you lose power, the encoder's reference point helps you start again fast.

Speed and Position Sensing

Incremental encoders are used to measure speed and position. They give feedback right away, which is important for fast-moving machines.

Here are some good things about using incremental encoders:

1. They cost less than absolute encoders, so you save money.

2. The hardware is simple and easy to use.

3. You can use them with many kinds of machines.

4. They give high resolution and accuracy for good control.

5. You can change the output to fit your needs.

6. You get different signal types, like HTL, TTL, or sine/cosine.

If you wonder, "where are incremental encoders used," remember they fit almost any machine that needs to know speed and position. The good things about incremental encoders are that they are strong, give quick feedback, and are easy to use. You can trust them for speed and distance in many jobs.

Incremental vs. Absolute Encoders

Operation Differences

Incremental encoders and absolute encoders work in different ways. Incremental encoders send out pulses when the shaft moves. These pulses come from marks on a disc. You get two or three channels, like A, B, and sometimes Z. The signals can be digital or analog, such as TTL, HTL, or sine/cosine waves. You have to count the pulses to know how far or fast something moves.

Absolute encoders use special patterns on the disc. Each spot has its own code. The encoder sends this code as bits or bytes through a serial interface. You always know the exact position, even after turning the power back on.

The main difference is that incremental encoders track movement, but absolute encoders always tell you the exact spot.

Data Retention

You should think about what happens if you lose power. Incremental encoders forget their position when power is lost. You must run a homing routine to find the starting point again. This takes extra time and can slow down your work.

• Incremental encoders lose position after power loss.

• You must re-home the system to start again.

• Absolute encoders keep the exact position, even after power loss.

• You get the correct position right away when you turn the power back on.

• Absolute encoders use unique codes for each spot, so you never lose track.

If you want to avoid delays after power loss, absolute encoders are a better choice.

Application Suitability

You need to pick the right encoder for your job. Incremental encoders are good if you want to save money and need a simple setup. They work well for speed, direction, and relative position tasks. You see them in conveyor belts, simple robots, and machines that can run a homing routine at startup. They cost less and take up less space.

Absolute encoders are best when you must know the exact position all the time. You use them in robotics, medical devices, and machines that cannot stop for homing. They help you save time and avoid mistakes after power loss.

Use incremental encoders for:

• Pulse counting

• Speed and direction monitoring

• Systems that can re-home after shutdown

Use absolute encoders for:

• Machines needing instant position after power-up

• Complex automation where downtime is costly

• Safety-critical systems

Think about what you need. If you want simple, low-cost feedback and can re-home, pick incremental. If you need instant, reliable position data, choose absolute.

Choosing Incremental Encoders

Application Needs

You need to match the encoder to your job. Start by thinking about what you want to measure. Is it a spinning shaft or a moving part in a straight line? You also need to look at where you will use the encoder. Some places have dust, oil, or water. Others have strong shaking or heat. You must pick an encoder that can handle these things.

Here is a table to help you see what to check:

Tip: You should always check the IP rating if you work in a place with dust or water.

You also need to think about how you will connect the encoder. Some jobs need the encoder on the motor shaft. Others need it on the load. The way you mount it can change the type you need.

Selection Tips

You want to choose the right encoder for your machine. Use these steps to help you decide:

1. Decide if you need to measure spinning (rotary) or straight movement (linear).

2. Check the environment. If you see dust, oil, or water, pick a magnetic encoder. Optical types work best in clean places.

3. Pick the right resolution. High resolution gives you more detail, but it may cost more.

4. Match the signal type to your controller. TTL, HTL, or sine/cosine signals must fit your system.

5. Use shielded cables and differential signals if you have long cable runs or lots of electrical noise.

6. Think about the need for an index channel. It helps you find a reference point after power loss.

7. Choose covers or bases that protect the encoder from dust and shaking.

8. Do not pick a more complex encoder than you need. Simple models work well for many jobs.

Note: Always check the mounting and cable length. Long cables can weaken signals. Use the right cable type to keep your data strong.

You can use this checklist to make sure you pick the best encoder for your needs. If you follow these steps, you will get reliable feedback and keep your machines running smoothly.

Incremental encoders let you follow movement with digital or analog pulses. Many machines use these devices for a few reasons. They are simple and do not cost much. They give steady speed and position feedback. You can use them in dirty or clean places. They send out signals like A, B, and Z channels. These signals help you know direction and find the starting spot.

You should always look at encoder details, like resolution and output type. This helps you pick what fits your job. Technical guides and kits let you try things out. They help you learn and make good choices for your projects.

FAQ

What is the main job of an incremental encoder?

An incremental encoder helps you follow movement. It changes motion into electrical signals. These signals let you check speed, distance, and direction. You use this information to control machines.

Can you use incremental encoders in dirty or wet places?

Yes, you can use them in those places. Many have tough cases and high IP ratings. Always check the IP rating before you put it in. Magnetic types work best in dirty or wet spots.

Tip: Pick an encoder that fits your work area.

How do you know which direction something moves?

You check the A and B signals. If A comes before B, you move forward. If B comes before A, you move backward. This way is called quadrature detection.

What happens if you lose power while using an incremental encoder?

You lose where you are. You must run a homing routine to find the start again. The Z channel helps you set the starting spot after power comes back.

Note: Absolute encoders remember position even if power goes out.