Encoder technology spans a wide spectrum—from simple magnetic sensing to ultra-high-resolution digital devices. Let’s walk through the fundamentals, starting with low-resolution Hall effect sensors and building up to advanced 20-bit absolute encoders. Along the way, we’ll clarify how bits, bytes, and digital resolution all fit together.
Hall Effect Sensors: A Basic Form of Rotary Encoder
Hall effect sensors are a common low-resolution encoder technology used in cost-sensitive or rugged environments. While not suitable for applications requiring fine precision, they’re ideal for detecting relative motion or coarse position.
How They Work:
- A magnet is attached to a rotating shaft.
- Three Hall sensors are arranged around the magnet to detect changes in the magnetic field.
- As the shaft rotates, the sensors output binary high/low (1/0) signals based on the field changes.
- These signals form a binary pattern used to detect the shaft’s position within one electrical cycle.
Resolution:
- A standard three-sensor Hall effect system can produce six unique states per electrical cycle.
- With multiple magnetic poles on the rotor, resolution increases (e.g., 6 states × 10 pole pairs = 60 steps/rev).
- This data is stored in memory as binary bits.
Bits & Bytes: How Position is Stored Digitally
Now that we have a basic encoder producing binary states, how do we store and interpret that data?
- Bit: A binary digit—either
0or1. It’s the smallest unit of digital information. - Byte: A group of 8 bits (e.g.,
10101100). A byte can represent 256 unique values (2⁸). - Word: A group of 16 or 32 bits, depending on the system.
These digital building blocks allow systems to store and compare positional data—whether it’s from a Hall sensor or a high-precision encoder.
Moving Up the Ladder: What Is a 20-Bit Encoder?
A 20-bit absolute encoder represents a significant leap in precision. It divides a full 360° shaft rotation into 2²⁰ = 1,048,576 unique positions. That’s over a million discrete steps per turn.
How It Works:
- Each shaft position is encoded as a unique 20-bit binary number.
- Even if the system loses power, the encoder remembers its position (unlike incremental encoders, which require recalibration).
- Ideal for applications like CNC machines, medical robotics, or semiconductor automation—where absolute position accuracy is essential.
Incremental vs. Absolute Encoders
| Encoder Type | Definition | Resolution Format | Retains Position on Power Loss? |
|---|---|---|---|
| Incremental | Outputs pulses as shaft turns | Pulses Per Revolution (PPR) | ❌ No |
| Absolute | Outputs a unique digital code for each shaft position | Bits (e.g., 12-bit, 20-bit) | ✅ Yes |
Single-Turn vs. Multi-Turn Absolute Encoders
- Single-Turn: Measures position within one rotation. Position resets every 360°.
- Multi-Turn: Tracks total rotations over time. Uses gears, battery backup, or Wiegand effect to remember turns.
These encoders store both angular position and full-turn count—essential for robotics, automated storage systems, and industrial automation.
Summary: Why This Matters
Understanding the relationship between sensor resolution and digital storage is critical to selecting the right encoder:
- Hall effect sensors are great for low-resolution, low-cost applications.
- Encoder outputs are stored and processed using bits and bytes.
- High-resolution absolute encoders (like 20-bit models) enable ultra-precise motion tracking and positioning.
Whether you’re building a basic conveyor system or a precision robotic arm, choosing the right resolution and understanding its digital implications ensures your system runs accurately and reliably.