3 ms·

> If you have two sensors and one is acting up, how do you know which one is true and which one is false? Typically it is possible to determine this by looking

> If you have two sensors and one is acting up, how do you know which one is true and which one is false? Typically it is possible to determine this by looking at reading stability. If one sensor is constantly stuck or changes values too fast (0-100% several times per second) or too slow, you know it's faulty. Those sensors should be engineered so that you can know if it's faulty. If you can't detect faulty sensor, it's just bad engineering.

Johnny555 8y ago
If you have 2 sensors, how do you reliably detect that one of them is bent or installed incorrectly and gives an inaccurate, but stable, reading? If the sensor is completely malfunctioning it's easier to detect, but what about when it's just wrong?
- yetihehe 8y ago
  > how do you reliably detect that one of them is bent or installed incorrectly During standard pre-launch or manufacturing tests. It should be verified by applying some change and checking that this change is measured correctly. Generally for critical sensors, you can add some circuitry or even mechanical means of checking (eg heater on temperature sensor). If mechanical side fails, whole sensor module is marked as failed. Critical sensors should be designed in a way that you know when it fails.
- hanniabu 8y ago
  You can also have 3 sensors and use a simple 2 of 3 check. The likeliness of 2 failing at the same time would probably be pretty low.
- chopin 8y ago
  For many sensors especially critical ones there are multiple independent ones (like indicated airspeed). If they deviate there are standard procedures to determine which one(s) are faulty. For IAS you basically set a determined thrust at a determined pitch. Then you have a table which gives you IAS for the altitude you are at. This will determine the faulty pitot tube. I think for other sensors there are similar procedures.

Johnny555 8y ago

If you have 2 sensors, how do you reliably detect that one of them is bent or installed incorrectly and gives an inaccurate, but stable, reading? If the sensor is completely malfunctioning it's easier to detect, but what about when it's just wrong?

yetihehe 8y ago
> how do you reliably detect that one of them is bent or installed incorrectly During standard pre-launch or manufacturing tests. It should be verified by applying some change and checking that this change is measured correctly. Generally for critical sensors, you can add some circuitry or even mechanical means of checking (eg heater on temperature sensor). If mechanical side fails, whole sensor module is marked as failed. Critical sensors should be designed in a way that you know when it fails.
hanniabu 8y ago
You can also have 3 sensors and use a simple 2 of 3 check. The likeliness of 2 failing at the same time would probably be pretty low.
chopin 8y ago
For many sensors especially critical ones there are multiple independent ones (like indicated airspeed). If they deviate there are standard procedures to determine which one(s) are faulty. For IAS you basically set a determined thrust at a determined pitch. Then you have a table which gives you IAS for the altitude you are at. This will determine the faulty pitot tube. I think for other sensors there are similar procedures.