Balanced Circuit Common Mode Signal Parameter Detection

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Solution Overview

Problem

Conventional balanced circuits face challenges in accurately determining parameter values due to noise and interference, as they often rely on differential voltage measurements that can be affected by inequalities in signal line impedances, leading to incomplete cancellation of noise and interference signals.

Innovation Solution

The method involves positioning a device with a balanced circuit sensitive to environmental changes, measuring a voltage correlated to the common mode signal, and using this measurement to determine the parameter value, such as temperature, by employing a Wheatstone bridge circuit with variable resistors and compensation circuitry to account for ambient temperature changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If differential voltage measurements are used to determine parameter values in a balanced circuit, then the measurement can be made, but noise and interference signals are not fully cancelled due to inequalities in signal line impedances

Engineering Contradiction:

Improveparameter value determination accuracyVSAvoidnoise and interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent converts the previously harmful common mode signal into a useful measurement parameter. By measuring the common mode voltage and using it to determine the parameter value, the system turns what was considered unwanted interference into the primary measurement signal, thereby eliminating the need for differential voltage measurements that are susceptible to noise cancellation errors.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

Instead of measuring the differential voltage and attempting to cancel noise through impedance matching, the patent inverts the approach by measuring the common mode voltage directly. This inversion of the measurement strategy eliminates the dependency on noise cancellation and provides more accurate parameter determination.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If common mode voltage is monitored relative to target voltage or differential gain, then the balance of the circuit can be checked, but the parameter value cannot be determined

Engineering Contradiction:

Improvecircuit balance verificationVSAvoidparameter value determination

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent makes the common mode voltage measurement serve multiple functions: it simultaneously verifies circuit balance and determines the parameter value. By using the common mode voltage as both a balance indicator and a measurement parameter, the system eliminates the need for separate measurement approaches and achieves both reliability and precision.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If separate sensors are used to determine parameter values, then accurate measurements can be obtained, but device complexity increases

Engineering Contradiction:

Improveparameter value determination accuracyVSAvoidsensor quantity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent enables the balanced circuit to perform multiple functions using a single sensor. By measuring the common mode voltage, the circuit simultaneously determines parameter values and verifies balance, eliminating the need for separate sensors and reducing overall device complexity while maintaining measurement precision.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 approach allows for accurate determination of parameter values by isolating and utilizing common mode signals, enhancing the accuracy of measurements and potentially reducing the need for separate sensors, thus improving the functionality and reliability of balanced circuit sensors.

Implementation Method 1

a resistive sensor having a Wheatstone bridge circuit with at least two variable resistors... positioning the resistive sensor such that the at least two variable resistors of the Wheatstone bridge circuit are arranged in an environment in which temperature is to be determined

Methodology Applied

Scientific EffectResistive sensor temperature sensitivity: Piezoresistive Effect

Data Source

PatentUS9429479B2Methods, devices, and systems which determine a parameter value of an object or an environment from a voltage reading associated with a common mode signal of a balanced circuit

Publication Date: 2016.08.30 MILLAR INSTR INC

AI summary

A method for determining a value of a parameter of an object or an environment includes positioning a device having a balanced circuit in or on an object or within a particular environment, wherein the balanced circuit comprises elements which are operationally sensitive to changes in a parameter of the object or the environment. The method further includes measuring a common mode signal of the balanced circuit and determining, from the common mode signal, a value of the parameter. An exemplary implementation of the method includes determining temperature using a resistive sensor having a Wheatstone bridge circuit with two variable resistors and two fixed resistors. Embodiments of systems and devices configured to employ such methods are provided, particularly medical probes, electronic signal monitoring devices, and systems employing such devices.