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LCR impedance measurement repeatability (Agilent 4285A)

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mawyatt:
Your hand is creating a complex and variable impedance with the DUT coil. For repeatable and realistic results you need a constant environment and setup.

If you study how Lab Bench LCR meters operate, with high "Q" components the measurement phase approaches +- 90 degrees which is highly sensitive region for computing the various DUT parameters and prone to error and complete nonsense. The measured magnitude of "Z" is usually good but the distilled values for the equivalent component (R) for loss is highly sensitive.

If one thinks about what's happening under these conditions, anything such as a slight change in measurement fixture length (moving a cable or wire), or DUT contact point (effects DUT length), or environment (hands and other stuff) can slightly change the measurement angle, and around 90 degrees for high "Q" DUT this significantly influences the loss component computed from the complex impedance Z.  We often "see" results of negative R with very high "Q" components with our IM3536.

Best

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