Tweezer LCR-Meter Technology for Quick Sub-1 pF and 10 nH Measurements

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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