Variable Reluctance Speed Sensor Digitization Circuit
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Solution Overview
Problem
Variable reluctance speed sensors generate low output voltage signals at low engine speeds, making them difficult to accurately measure due to high temperature environments and the need for extensive filtering and amplification, which increases weight and wire count when incorporating signal conditioning circuitry.
Innovation Solution
A speed sensor with a digitization circuit housed within the sensor to convert sinusoidal output signals into digital signals, using a remotely positioned power supply and a two-wire connection to reduce the need for extensive filtering and amplification in the engine control circuitry, employing a digitization circuit with a blocking capacitor, full wave rectifier, and NPN switching transistor to maintain constant amplitude and proportional frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal conditioning circuitry is incorporated within the speed sensor, then measurement precision is improved, but device complexity and weight increase
Solution Approach 1:
The patent extracts the signal conditioning circuitry from the speed sensor housing and places it in the engine control circuitry instead. This separation allows the sensor to remain simple while still benefiting from signal processing, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent introduces an intermediary approach by using a two-wire connection that carries both power and signal. This intermediary communication path enables the remotely positioned signal processing circuitry to effectively process sensor output without requiring the processing circuitry to be physically integrated with the sensor, thus maintaining simplicity while achieving accurate measurement.
2Measurement precision
If signal conditioning circuitry is incorporated within the speed sensor, then measurement precision is improved, but weight increases
Solution Approach 1:
The patent removes the signal conditioning circuitry from the speed sensor and relocates it to the engine control circuitry. This extraction significantly reduces the weight of the speed sensor assembly while maintaining the ability to process signals accurately through remote circuitry.
3Measurement precision
If signal conditioning circuitry is incorporated within the speed sensor, then measurement precision is improved, but the number of wires increases
Solution Approach 1:
The patent merges the power supply and signal transmission into a single two-wire connection. By combining these functions into one communication path, the patent eliminates the need for separate wiring for power and signal conditioning, thus reducing the number of wires while enabling remote signal processing.
4Ease of operation
If the sensor output is provided to remote signal-processing circuitry, then ease of operation is improved, but measurement precision deteriorates at low speeds
Solution Approach 1:
The patent applies preliminary action by incorporating signal amplification and conditioning circuitry that activates before the signal reaches the engine control circuitry. This preliminary processing ensures that even weak low-speed signals are boosted to adequate amplitude levels, maintaining measurement precision while allowing remote circuitry processing.
Solution Approach 2:
The patent uses parameter changes by dynamically adjusting signal amplitude through amplification circuitry based on the operating conditions. The signal processing circuitry compensates for low-speed conditions by increasing gain, thereby maintaining consistent measurement precision across the full range of operating speeds while preserving the benefit of remote processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides a cost-effective and reliable method for measuring machine speed by reducing the complexity of engine control circuitry and maintaining consistent output voltage across varying engine speeds without increasing the number of wires, allowing for efficient processing of digital signals in harsh environments.
Implementation Method 1
a magnetic field produced by the sensor is disrupted, producing a sinusoidal voltage signal
Implementation Method 2
a blocking capacitor which blocks a DC bias voltage from reaching the variable reluctance sensor
Implementation Method 3
a full wave rectifier which converts the AC voltage to an absolute value voltage signal
Implementation Method 4
an NPN switching transistor which switches the voltage signal in response to the absolute value voltage signal
Implementation Method 5
the digitization circuit is configured to amplify the voltage signal to provide a substantially constant amplitude output
Data Source
AI summary
A method and system for measuring a characteristic of a machine is provided. The system includes a speed sensor including a housing, a variable reluctance sensor (VRS) mounted at least partially within the housing, and a digitization circuit electrically coupled to an output of the VRS. The digitization circuit is also mounted within the housing and is configured to convert a substantially sinusoidal output of the VRS into a digital output signal.