What Is A Sensor Resolver? How Does It Differ From A Magnetic Encoder?

A sensor resolver is a signal component whose output voltage varies with the rotor angle. It operates based on the principle of electromagnetic induction. As the rotor and stator positions change, the output signal modulates the phase and amplitude of the input sine wave carrier signal. This modulated signal is then processed by dedicated signal processing circuits or certain DSP and microcontrollers with appropriate interfaces. The relationship between the output signal's amplitude and phase and the sine wave carrier signal is used to determine the angular position between the rotor and stator.

A typical magnetic encoder uses grating principles and employs photoelectric methods for angular position detection. It can be divided into incremental and absolute types.

### Principles of Operation

- **Sensor Resolver**: Works on the principle of electromagnetic induction. The output signal modulates the input sine wave carrier signal's phase and amplitude based on the rotor and stator positions. This signal is processed to determine the angular position.

- **Magnetic Encoder**: Typically uses grating principles and photoelectric methods for angular position detection, further categorized into incremental and absolute types.

### Types and Characteristics

- **Sensor Resolver**:

- Available in single-pole and multi-pole types, with the latter often referred to as n-speed.

- Within the angular range of one pole pair (a full circle for single-pole), the processed signal reflects the absolute position, indicating the current angle within 0-360 degrees (electrical angle).

- Commercial resolutions can achieve up to 2^12 or even 2^16.

- Constructed from silicon steel sheets and enameled wire, without any electronic components, providing excellent vibration resistance and temperature characteristics.

- Superior performance in harsh environments compared to typical magnetic encoders, making them widely used in military applications.

- **Magnetic Encoder**:

- Uses grating principles and photoelectric methods for angular position detection.

- Divided into incremental (measuring angular displacement increments relative to a previous point) and absolute types (measuring total angular displacement from the start).

### Output and Environmental Tolerance

- **Sensor Resolver**:

- Outputs sine and cosine signals, with phase difference calculated through a chip.

- Capable of handling high speeds, up to tens of thousands of RPM.

- Operating temperature range: -55°C to +155°C.

- **Magnetic Encoder**:

- Typically outputs square waves.

- Limited to lower speeds compared to sensor resolvers.

- Operating temperature range: -10°C to +70°C.

### Main Differences

1. **Precision and Output**:

- **Encoder**: Uses pulse counting for precise measurements.

- **Sensor Resolver**: Provides analog feedback rather than pulse counting.

2. **Signal Type**:

- **Encoder**: Generally outputs square waves.

- **Sensor Resolver**: Outputs sine and cosine signals, with phase difference decoded by a chip.

3. **Speed**:

- **Sensor Resolver**: Capable of higher rotational speeds.

- **Encoder**: Limited to lower rotational speeds.

4. **Operating Environment**:

- **Sensor Resolver**: Tolerates a broader temperature range (-55°C to +155°C).

- **Encoder**: Limited to -10°C to +70°C.

5. **Application**:

- **Sensor Resolver**: Generally incremental type.

- **Encoder**: Can be both incremental and absolute, with differences in precision for small and large angles.

In essence, the fundamental difference lies in the type of signal: digital pulses for encoders versus analog sine/cosine signals for sensor resolvers.