As a robust, contactless, and relatively low-cost angular position sensor, Variable Reluctance Resolver (VRR) is widely used in fields such as motor control, robotics, aerospace, and industrial automation. To ensure its reliability and accuracy, the following key issues need to be noted during the application process:

1. Mechanical installation and alignment:

Concentricity and perpendicularity: This is the most important point. The air gap between the stator and rotor (salient poles) of VRR is very small and uniformity is crucial for signal quality. During installation, it is necessary to ensure strict concentricity and perpendicularity (i.e. axial parallelism) between the stator and the rotor shaft (or the measured shaft). Excessive eccentricity or tilt can lead to:

Asymmetric and distorted output signal amplitude: sine and cosine signals have unequal amplitudes and distorted waveforms.

Angle measurement error increases: significant nonlinear errors are introduced, resulting in a serious decrease in accuracy.

Zero drift: The mechanical zero point varies with installation errors.

Installation stiffness and vibration: The installation structure must have sufficient stiffness to avoid deformation or relative displacement during operation (especially in high-speed or vibration environments), otherwise dynamic errors and noise may be introduced. Vibration reduction measures should be considered.

Axial clearance: The axial clearance (end clearance) between the stator and rotor must be strictly controlled according to the specifications. Excessive clearance can weaken the signal, while insufficient clearance may cause friction or even jamming.

Thermal expansion effect: Consider the differences in thermal expansion coefficients of different materials (shaft, bearing seat, sensor body) during system operation to avoid changes in air gap or stress caused by thermal expansion.

2. Electrical interfaces and incentives:

Excitation signal:

Frequency: The excitation frequency specified in the sensor specification must be used. Frequency deviation can affect the demodulation accuracy and the phase relationship of the output signal.

Amplitude: The amplitude of the excitation voltage or current must be within the specified range. Too low can lead to poor signal-to-noise ratio, while too high may cause magnetic core saturation or heating.

Waveform quality: The excitation signal should be as pure as possible (low harmonic distortion, low noise), avoiding the use of signals containing rich harmonics such as square waves (unless allowed by the design), otherwise it will introduce measurement noise and errors.

Stability: The frequency and amplitude of the excitation signal require high stability.

Demodulation circuit (RDC or DSP):

Compatibility: The selected rotary digital converter or digital signal processing algorithm must be compatible with the type of VRR (usually two-phase output) and excitation frequency.

Accuracy and bandwidth: The accuracy and bandwidth of RDC/DSP need to meet the system requirements. Bandwidth affects dynamic response speed.

Tracking rate: The maximum tracking rate of RDC needs to be greater than the maximum speed of the tested shaft (considering electrical speed).

Reference phase compensation: There may be a phase delay in the excitation signal to the RDC reference input terminal, and compensation settings need to be made, otherwise a fixed offset error will be introduced.

Cable and Connection:

Shielding: It is strongly recommended to use shielded twisted pair cables (one pair each for excitation, Sin, Cos) and ground the shielding layer at a single point on the sensor end (usually at the controller/RDC end) to effectively suppress electromagnetic interference.

Length: Long cables can increase distributed capacitance and resistance, which may cause signal attenuation, phase shift, and noise pickup. The maximum allowable length should be determined based on the specifications or actual testing, and if necessary, the use of driver circuits should be considered.

Connection reliability: Ensure that all connectors have good contact and avoid virtual soldering and loosening.

3. Environmental adaptability:

Temperature:

Temperature drift: The output signal amplitude and zero point of VRR may vary with temperature. Although smaller than traditional rotary temperature drift, high-precision applications still require attention. Choose models with good temperature drift indicators, or perform temperature compensation in the system.

Scope of work: Ensure that sensors and connectors (such as sealant) can function properly within the temperature range of the application environment.

Humidity and pollutants: VRR itself usually has a high protection level (IP67/IP69K is common), but attention should be paid to the protection of the connector interface. Ensure the sealing of connectors in environments such as humidity, oil stains, dust, and chemical corrosion.

Electromagnetic compatibility:

Anti interference: VRR signal level is low and susceptible to strong electromagnetic field interference (such as nearby high-power frequency converters, motors, and switching power supplies). Good shielding (cables and sensor housings) and distance from interference sources are key. If necessary, filtering can be added before the signal enters RDC.

Radiation: The excitation signal itself is also a radiation source, and good shielding can help reduce its interference with external devices.

Vibration and shock: Ensure that the sensor and its installation can withstand the vibration and shock levels in the application environment, avoiding internal structural damage or loose connections.

4. Signal processing and calibration:

Signal conditioning: Before the signal enters RDC/DSP, a preamplifier (gain) or filter (anti aliasing, bandpass filtering) may be required.

System calibration:

Zero/offset calibration: After installation or replacement of the sensor, electrical zero calibration must be performed at the known mechanical zero position to eliminate installation errors and small offsets in the sensor itself.

Amplitude balance: Adjust or ensure that the gains of Sin and Cos channels are consistent to avoid ellipse fitting errors.

Orthogonal calibration: Although VRR itself has good orthogonality, the circuit or solution may introduce small orthogonal errors, which high-precision systems may need to compensate for.

Angle calculation error compensation: For ultra-high precision requirements, it may be necessary to perform nonlinear error compensation based on measured data (such as lookup tables).

5. Other precautions:

Demagnetization: In extreme situations (such as experiencing strong external magnetic fields), the iron core material may have slight residual magnetism, which affects accuracy. Usually, the impact is not significant, but if suspected, demagnetization treatment can be carried out according to the manufacturer's recommendations (such as applying a reverse attenuated alternating field).

Overload protection: Avoid excitation voltage/current exceeding the maximum value, prevent coil overheating or damage.

Sensor selection: Choose the appropriate model based on application requirements (accuracy level, speed range, temperature range, protection level, external dimensions, electrical interface).

All models of MIC sensors' reluctance rotary transformers undergo strict testing and inspection during production control and before leaving the factory to ensure stable operation in various extreme environments. And we have collaborated with several well-known new energy vehicle brands such as BYD, Changan, Dongfeng, Xiaopeng, etc., and have confirmed the stability, accuracy, consistency, and durability of our products in practical applications.

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