Resistance Measurement with Series Diode Error Elimination
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Solution Overview
Problem
Existing resistive temperature sensors face inaccuracies when measuring resistance in the presence of a series diode, as the diode introduces an unknown voltage drop, limiting their applicability, especially in matrix applications.
Innovation Solution
The technique involves switching currents between three levels (I1, I2, I3) across the resistive element and diode, using measuring circuitry to combine voltages measured at each current level to partially eliminate the error caused by the diode voltage drop, thereby accurately determining the resistance of the resistive element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single current is supplied to measure resistance, then the measurement is simple, but the error caused by diode voltage drop is significant
Solution Approach 1:
The measurement process is segmented into three distinct current levels (I1, I2, I3) rather than using a single current. Each current level provides a measurement that, when combined through the formula V1 - 2V2 + V3, eliminates the diode voltage drop error. This segmentation transforms a single inaccurate measurement into multiple measurements that can be processed to achieve high precision.
Solution Approach 2:
The current parameter is changed across three different values (I1, I2, I3) instead of maintaining a constant current. By varying the current parameter and measuring the corresponding voltages, the system can mathematically eliminate the diode voltage drop component and extract the accurate resistance value of the resistive element.
2Measurement precision
If three current levels are used to eliminate diode error, then measurement precision improves by several orders of magnitude, but device complexity increases
Solution Approach 1:
The measurement system employs periodic switching between three current levels (I1, I2, I3) in a cyclic manner. This periodic action allows the measuring circuitry to sequentially apply different currents and combine the resulting voltages (V1, V2, V3) using the formula V1 - 2V2 + V3, achieving high precision resistance measurement while managing circuit complexity through time-multiplexed operation.
3Adaptability or versatility
If diodes are added in series for matrix applications, then adaptability improves, but measurement accuracy deteriorates due to unknown voltage drop
Solution Approach 1:
The diode voltage drop, which was previously a harmful factor causing measurement errors, is converted into a benefit through the three-current measurement technique. By measuring at three different current levels and combining the results as V1 - 2V2 + V3, the diode voltage drop components cancel out mathematically, transforming the diode from a source of error into an enabler for matrix applications with accurate temperature sensing.
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 significantly reduces the error in resistance measurement, achieving several orders of magnitude improvement over single-current methods, allowing for precise temperature sensing despite the diode's influence, and is particularly useful in matrix configurations.
Implementation Method 1
one use is as a temperature sensor, exploiting the variation in resistance with temperature
Implementation Method 2
the diode introduces an unknown voltage drop
Data Source
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AI summary
A technique for measuring the resistance of a resistive element (4) in the presence of a series diode (10) is provided. By supplying three different currents I1, l2, l3 and measuring corresponding voltages V1, V2, V3 across the resistive element (4) and diode (10), the voltages can be combined to at least partially eliminate an error in the measured resistance of the resistive element (4) caused by a voltage drop across the diode (10). A technique for current control in an array of resistive elements (60) is also described in which a column of resistive elements (60) is provided with two or more current sources (70, 72) switched so that while one current source (70) is providing current to the column line (66) corresponding to a selected resistive element (60), another current source (72) has its amount of current adjusted.