Current Measuring Device Parallel Compensating Resistor
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Solution Overview
Problem
The four-wire current measurement technique is affected by temperature dependence due to resistors in the voltage measurement loop, particularly in low-resistance applications, where copper or conductive materials exhibit high temperature coefficients, leading to inaccurate current measurements.
Innovation Solution
A current measuring device that divides the measured current into a main path through a resistor element and a secondary path through a compensating resistor connected in parallel, where the compensating resistor's resistance value is designed to counteract the temperature dependence of the conductor elements in the secondary path, ideally using the same or different materials to achieve compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a four-wire measurement technique is used with copper current connection parts, then the current measurement can be performed with low resistance, but the temperature dependence of the measurement increases due to the high temperature coefficient of the copper resistors in the voltage measurement loop
Solution Approach 1:
The voltage measurement loop is segmented into two separate loops: a first voltage measurement loop through the resistor element and a second voltage measurement loop through the compensating resistor. This segmentation allows independent optimization of each loop's temperature characteristics, enabling the compensating resistor to counteract the temperature dependence of the copper connection parts.
Solution Approach 2:
A compensating resistor is introduced as an intermediary element in the second voltage measurement loop. This compensating resistor, made of material with high temperature coefficient (such as copper), acts as a mediator that generates a compensating voltage signal to counterbalance the temperature-induced errors in the main measurement loop.
2Measurement precision
If copper or highly conductive materials are used in the voltage measurement loop, then the voltage measurement can be performed with low resistance, but the temperature coefficient of the resistance increases, leading to higher temperature dependence
Solution Approach 1:
The high temperature coefficient of copper, which is normally a harmful factor causing measurement errors, is converted into a beneficial effect. By using copper or copper-like material for the compensating resistor in the second voltage measurement loop, the temperature-induced resistance changes are transformed into a compensating signal that counteracts the temperature errors in the main measurement loop.
Solution Approach 2:
The resistance values of the resistor element and compensating resistor are specifically dimensioned to achieve optimal temperature compensation. The parameters (resistance values, temperature coefficients) are changed and optimized so that the positive temperature coefficient of the compensating resistor counterbalances the negative temperature coefficient effects in the main measurement path.
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 temperature dependence in current measurements, ensuring accurate and reliable readings by compensating for the temperature coefficients of both the resistor element and conductor materials, thereby improving measurement precision.
Implementation Method 1
a secondary current path through a compensating resistor (fixed resistor) which is electrically connected between the two voltage measurement terminals in parallel with the resistor element
Implementation Method 2
Due to the relatively high temperature coefficient of the resistance value of the conductor element in the secondary current path, the resistance value in the secondary current path increases with increasing temperature
Implementation Method 3
the electric voltage falling across the resistor element R0 is a measure of the electric current Ip or In in accordance with Ohm's law
Data Source
AI summary
The invention concerns a current measuring device for measuring an electric current (Ip, In) according to the four-wire technology with a low resistance current measuring resistor (RCu1, RCu, R0). The invention also provides for a compensating resistor (Rp) consisting of a fixed resistor connected in parallel with the resistor element (R0) of the low-resistance current measuring resistor (RCu1, RCu, R0) in order to at least partially compensate for the temperature dependence of the resistance value, so that the current measuring device has two current paths, namely a main current path through the resistor element (R0) on the one hand and a secondary current path through the compensating resistor (Rp) on the other hand.