Parallel Resistor Test Device for Impedance Matching
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Solution Overview
Problem
The existing test devices for verifying test signals to a Device Under Test (DUT) face input impedance mismatches, which can cause malfunction or damage to sensitive signal generators and result in different electrical signals being measured by measurement instruments compared to those provided to the DUT circuitry.
Innovation Solution
Incorporating a parallel resistor in parallel with the measurement output terminal of the test device, connected to a reference voltage potential node, to reduce the effective measurement input impedance of the electrical measurement instrument and the test device to match the DUT circuitry impedance, ensuring the input impedance of the test device is substantially equal to the DUT input impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a test device is used to verify test signals before providing them to a DUT, then measurement accuracy is improved, but input impedance mismatch causes harmful effects including signal generator malfunction and measurement errors
Solution Approach 1:
A parallel impedance element (resistor or capacitor) is introduced as an intermediary component between the test device and the measurement instrument. This intermediary component adjusts the effective input impedance to match the DUT input impedance, thereby eliminating impedance mismatch effects while enabling accurate test signal verification
Solution Approach 2:
The input impedance parameter of the test device is modified by adding parallel impedance elements. The resistance value or capacitance value is specifically selected to transform the effective input impedance to match the DUT input impedance, thereby resolving the impedance mismatch problem
2Object-affected harmful factors
If the test device has high input impedance to avoid loading the signal generator, then signal generator safety is improved, but the measured signal differs from the actual DUT signal
Solution Approach 1:
The input impedance parameter is dynamically adjusted by selecting specific resistance or capacitance values for the parallel impedance element. This transformation enables the test device to present a low effective input impedance that matches the DUT, ensuring accurate signal measurement while the signal generator remains protected during the verification phase
3Measurement precision
If a parallel impedance element is added to match input impedance, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The impedance matching function is segmented into a separate, modular parallel impedance element that can be independently selected and configured. This segmentation allows the core test device to remain simple while the impedance matching requirement is addressed by a dedicated component with specific resistance or capacitance value
Solution Approach 2:
The parallel impedance element uses simple, inexpensive passive components (resistors or capacitors) that can be easily selected from standard values. These basic components provide the necessary impedance transformation without requiring complex active circuits or expensive specialized parts
Data Source
AI summary
Systems, apparatuses, and methods for test devices having parallel impedances to reduce measurement input impedance are disclosed. An apparatus includes a test input terminal, a measurement output terminal, a reference voltage potential node, and a parallel resistor. The test input terminal is configured to electrically connect to a signal output terminal of a signal generator. The test input terminal is configured to receive a test signal from the signal generator via the signal output terminal. The measurement output terminal electrically connects to a measurement input terminal of an electrical measurement instrument. The parallel resistor is electrically connected from the measurement output terminal to the reference voltage potential node. A system includes the apparatus and the electrical measurement instrument. A method includes providing a test signal to the test device, verifying the test signal using the electrical measurement instrument, and providing the test signal to a device under test.