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A microcontroller-based lock-in amplifier for sub-milliohm resistance measurements.
1Department of Physics, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
The Review of Scientific Instruments
|August 3, 2012
Summary
A novel digital ohmmeter achieves high resolution (<60 μΩ) using a microcontroller and instrumentation amplifier. Its lock-in detection firmware enables precise measurement of low resistances without external signal generators.
Area of Science:
- Electrical Engineering
- Instrumentation and Measurement
Background:
- Accurate measurement of low resistances (micro-ohm range) is challenging.
- Traditional methods often require complex circuitry or specialized hardware.
Purpose of the Study:
- To present a novel, cost-effective digital ohmmeter design.
- To achieve high-resolution resistance measurements using a general-purpose microcontroller.
Main Methods:
- Design of a digital ohmmeter utilizing a microcontroller and instrumentation amplifier.
- Implementation of a firmware-based lock-in detection technique.
- Employing digital I/O pins to alternate current and discriminate signals.
Main Results:
- Achieved a resolution of less than 60 μΩ.
- Successfully detected microvolt drops across sample resistors as low as 55.6 μΩ.
- Demonstrated selective detection of signals out of phase/frequency with the reference.
Conclusions:
- The proposed design offers a simple yet effective solution for high-resolution digital ohmmeters.
- It eliminates the need for external reference signal generators and powerful processors.
- This approach is suitable for measuring very low resistances in various applications.
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