Analog Circuit Arrangement for Signal Testing

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Solution Overview

Problem

Implementing error detection for signals from incremental encoders using analog circuitry is complex due to the need for high circuitry complexity in mapping quadratic terms, which can lead to missed errors if the test value fluctuates within a permissible range.

Innovation Solution

An alternative calculation rule that does not include quadratic terms, such as |A|+|B|, is used to generate a test signal that fluctuates within a predetermined value range, reducing circuit complexity at the expense of accuracy, and an analog circuit arrangement is designed to implement this rule using operational amplifiers and diodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If quadratic terms are mapped using analog circuitry for error detection, then measurement precision is improved, but device complexity increases significantly

Engineering Contradiction:
Improveerror detection accuracyVSAvoidcircuitry complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent changes the mathematical parameter from quadratic terms (A²+B²) to absolute value terms (|A|+|B|). This parameter transformation maintains the ability to detect encoder errors while significantly simplifying the analog circuit implementation, avoiding the need for complex squaring circuits.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent employs simpler analog circuit components (absolute value circuits instead of quadratic term circuits) that are easier to implement and less complex. This substitution reduces circuit complexity while maintaining sufficient functionality for error detection in incremental encoders.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

2Device complexity

If an alternative calculation rule without quadratic terms is used, then device complexity is reduced, but measurement precision deteriorates due to permissible value range fluctuations

Engineering Contradiction:
Improvecircuitry complexityVSAvoiderror detection accuracy
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The patent implements a monitoring unit that continuously evaluates the test signal against expected ranges. This feedback mechanism compensates for the reduced precision of the alternative calculation rule by detecting when the fluctuating test signal deviates from its expected behavior, thereby maintaining error detection capability.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent accepts that the test signal will dynamically fluctuate within a permissible range rather than remaining constant. This dynamic approach allows the use of simpler circuits while the monitoring system adapts to the expected variations, distinguishing between normal fluctuations and actual errors.

Inventive Principle:
Principle #15Dynamics

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

The solution simplifies the circuitry required for error detection in analog circuits while allowing for detection of errors through a test signal that fluctuates within a defined range, suitable for incremental encoders and other devices with phase-shifted sine and cosine signals.

Implementation Method 1

The circuit design is selected in such a way that the partial currents occurring in the diode network cause an operating point in the curvature area of ​​the characteristic of the respective diodes, so that the partial currents are advantageously approximately squared

Methodology Applied
Scientific EffectDiode characteristic curvature effect: Diode

Implementation Method 2

Many mathematical functions can be easily built using pure analog technology if operational amplifiers are used

Methodology Applied
Scientific EffectOperational amplifier operation:

Data Source

PatentEP2627974B1Method, circuit arrangement and monitoring device for signal testing
Publication Date: 2018.04.25 PHOENIX CONTACT GMBH & CO KG
  • EP2627974B1 patent drawingFigure 1
  • EP2627974B1 patent drawingFigure 2

AI summary

For signal testing, in particular for the error checking of signals, the invention relates to a method for the signal testing of at least a first and a second analogue input signal (210, 220), wherein a rule is defined for determining an output signal (230) which fluctuates temporally within a predetermined value range (240), an analogue circuit arrangement (100) is provided which implements the rule, the at least one first and second analogue input signal (210, 220) is supplied to the circuit arrangement (100) and the output signal (230) is then evaluated to ascertain whether it lies within the predetermined value range (240). According to the invention a circuit arrangement (100) is also provided, in addition to a monitoring device comprising such a circuit arrangement (100).