Multi Coil Quadrature Demodulation Signal Chains for Proximity Measurement
Multi coil quadrature demodulation isolates amplitude and phase in inductive proximity chains, resolving sub-micron targets while rejecting thermal noise.
Low Pass Filtering
Frequency Selective Attenuation
Signal conditioning stages that permit low frequency components to pass while suppressing higher frequencies are essential for noise reduction. Analog or digital low pass filtering removes unwanted ripples from a sensor output. This process ensures that the subsequent data acquisition system captures only the relevant physical measurements.
The cutoff frequency defines the boundary where the signal begins to weaken.
Passive Network
Simple resistors and capacitors form the basis of most hardware filters. As frequency increases, the impedance of the capacitor drops, which shunts the signal to ground. Then low pass filtering provides a smooth output voltage that follows the slow changes of the measured variable.
Active filters using operational amplifiers can provide sharper transitions and higher gain.
Digital Integration
Microcontrollers often implement this function using moving averages or infinite impulse response equations. A digital version of low pass filtering offers flexibility because the parameters can change during operation without hardware modifications. Computation time increases with the complexity of the filter order.
Higher order filters provide steeper roll off rates but may introduce significant time delays that affect control loops in real time environments.
Delayed Response
Filtering always introduces a delay between a physical change and the sensor response. If the filter is too aggressive, the system may miss rapid events or transient peaks. Designers must find an equilibrium between a clean signal and a fast response.