1.1.3 Example: Partially Bad Sensor

An environmental sensor returns the correct temperature but not humidity.

Some possible causes:

• Incorrect application circuit or noisy power supply (Electrical)
• Insufficient time was provided for the sensor to complete the data processing (Protocol)
• Faulty sensor initialization or data processing (Application)

In this example, the sensor is partially working, eliminating many possibilities that would result in it not working at all. The first possibility to consider is an incorrect application circuit or a noisy power supply. The most likely symptom of this issue is the sensor providing seemingly valid data that is inaccurate or invalid. Similar behavior may occur if the sensor does not have enough time to complete processing before sending data.

Moving up to the Application level, faulty initialization or data processing may also fit the criteria. A poor initialization (or calibration) may lead to incorrect assumptions about the sensor performance/behavior. For instance, if the sensor ADC resolution is configurable, maybe the code expects resolution X, but Y has been set.

Another possibility is the data not processed correctly, which can be verified by either reading the raw values and manually checking the results or feeding in known results and checking to see if the output matches the expected results.