The voltage and current offsets of two typical precision operational amplifiers (OPAs) with BJT and FET input, respectively, were continuously measured for two years. The paper presents the experiment, explains the method of data analysis, and discusses the results. The long-term stability turns out to be limited mainly by random walk processes.

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At the National Institute of Metrological Research a convenient setup to verify the DMMs linearity has been developed. It consists in a top-class calibrated DC Voltage calibrator supplying directly the DMMs under test. Some Keysight 3458A, a Fluke 8508A and an 8588A DMMs are being enrolled in the tests. This setup is also compared with another setup with a Digital Analog Converter (R -2R DAC) in place of the calibrator. The DMMs linearity is being verified both when DMMs are just switched on and at thermal regime. The interference of the input stages of the DMMs connected in parallel during the linearity measurements and the linearity by inverting the plug of one of the DMMs connected in parallel are currently under verification.

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