Analog signature analysis

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Analog signature analysis is an electronic component and circuit board troubleshooting technique which applies a current-limited AC sinewave across two points of an electronic component or circuit.


The resulting current/voltage waveform is shown on a signature display using vertical deflection for current and horizontal deflection for voltage. This unique analog signature represents the overall health of the part being analyzed. By comparing the signatures of known good circuit boards to those of suspect boards, faulty nets and components can be quickly identified.

Analog Signature Analysis relies on a change in electrical characteristics to detect problems on a circuit board.

Other terms

Power-off testing is often necessary to test the printed circuit assembly (PCA) board due to uncertainty as to the nature of the failure. When the PCA can be further damaged by applying power it is necessary to use power off test techniques to safely examine it. Power off testing includes analog signature analysis, ohmmeter, LCR Meter and optical inspection. This type of testing also lends itself well to troubleshooting circuit boards without the aid of supporting documentation such as schematics.

Typical equipment

In the testing of printed circuit boards, a flying probe test or fixtureless in-circuit test (FICT) system may be used for testing low to mid volume production, prototypes, and boards that present accessibility problems. A traditional "bed of nails" tester for testing a PCB requires a custom fixture to hold the PCBA and the Pogo pins which make contact with the PCBA. In contrast, FICT uses two or more flying probes, which may be moved based on software instruction. The flying probes are electro-mechanically controlled to access components on printed circuit assemblies (PCAs). The probes are moved around the board under test using an automatically operated two-axis system, and one or more test probes contact components of the board or test points on the printed circuit board.

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