Elevator Mechanic Practice Exam

When you observe a saw tooth wave on an oscilloscope while checking an encoder, what action should you take?

1. Check for a fault in the encoder

2. Increase the operating frequency

3. Replace the oscilloscope

4. Recalibrate the system

The correct answer is: Check for a fault in the encoder

The appearance of a sawtooth wave on an oscilloscope when checking an encoder typically indicates that the encoder may be malfunctioning, as this waveform suggests a problem in the signal pattern that should reflect the expected smooth transitions of an incremental encoder or a clean square wave from a quadrature encoder. This could be due to various issues such as signal interference, mechanical alignment problems, or wear and tear in the encoder itself. Therefore, the most appropriate action to take is to check for a fault in the encoder. Doing so allows you to diagnose the underlying issue directly, which could involve inspecting connections, testing with another encoder, or evaluating the encoder's physical condition. Other options focus on addressing symptoms rather than diagnosing the root cause of the irregular waveform.