Digital LCR-meters are subject to both sudden failures and gradual failures. Off-line testing methods used for these devices can detect their improper operation caused by any of these two types of failures. However, an LCR-meter is normally tested only on a few input values. This does not guarantee fault free operation in the other "points" of the measurement band or in another mode of operation of the meter. In the present work, we attempt to resolve this issue by considering a concurrent approach to testing of LCR-meters. The approach is based on checking some invariant properties available in direct-conversion LCR-meters. After detecting a failure, the algorithm proceeds to the off-line diagnosis of the digital part of the meter. It is shown how to adapt a signature analysis method for diagnosis of "erroneous" scan chains residing in the digital part. Under certain conditions, the number of required signatures is reduced, preserving the diagnosis resolution and the aliasing rate.
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