White PaperElectronics & Computers
Tweezer LCR-Meter Technology for Quick Sub-1 pF and 10 nH Measurements
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Tweezer-style LCR meters have gained significant popularity in recent years. However, a common limitation among all models is the presence of parasitic inductance and capacitance in unshielded test leads, which hinders the precise measurement of very small inductances and capacitances. These parasitic effects vary depending on the distance between the test leads that is the size of the component being tested.
Lately, various studies have been conducted to enhance the accuracy of tweezer-style LCR meters for measuring small capacitance and inductance values. While improving capacitance measurements was relatively straightforward, refining inductance measurements proved more challenging.
The primary source of inaccuracy in both cases is the parasitic capacitance and inductance of unshielded test leads. Without shielding, the AC test signal generated by the meter interacts electromagnetically with the test leads, creating parasitics. While negligible for larger components, these parasitic effects can exceed the values of smaller components, leading to significant measurement errors.
Developing a method to compensate for parasitic capacitance and inductance offsets enables LCR meters to measure much smaller components accurately. Siborg Systems has addressed this challenge by introducing Open and Short Calibration Boards, which have proven to be an effective solution for extending measurement range all the way down to 0.1 pF and 1 nH.
The figure above illustrates the source of parasitic inductance and capacitance in test leads. By applying proper offset adjustments with the shown Calibration Boards, measurement accuracy is greatly enhanced, allowing tweezer meters to rival the performance of much more expensive benchtop devices.
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Overview
The white paper from Siborg Systems Inc. discusses advancements in tweezer-style LCR meters, specifically focusing on improving the accuracy of measurements for small capacitance and inductance values. It highlights the challenges faced in measuring these small values due to parasitic effects from test leads, which can lead to significant measurement errors if not properly calibrated.
The document emphasizes the importance of calibration, particularly for two-wire measurement setups, as demonstrated in various IEEE publications. It notes that without proper calibration, the relative measurement error for inductances below 10 nH can exceed 100%. The paper showcases how Siborg's proprietary open/short calibration boards can effectively eliminate these parasitic offsets, enabling accurate measurements of capacitance below 1 pF and inductance below 10 nH.
Key features of the LCR-Reader-MPA are outlined, including its ability to perform L-C-R/ESR measurements, AC/DC voltage/current measurements, and its functionality as an oscilloscope and signal generator. The device operates within a test frequency range of 100 Hz to 100 kHz and offers a basic accuracy of 0.1%. It also includes features such as component sorting, super capacitor testing, and an optional Bluetooth module.
The paper presents data demonstrating the effectiveness of calibration in enhancing measurement accuracy, with specific examples comparing measurements with and without correction. It concludes by underscoring the critical role of proper calibration in achieving reliable results in small capacitance and inductance measurements, thus reinforcing the value of Siborg's technology in the field of electronic testing.
Overall, the white paper serves as a comprehensive overview of the technological advancements in tweezer-style LCR meters, emphasizing the significance of calibration in improving measurement precision for small electronic components.