Screen outliers in sensor values outside the plausible range of measurement.

[#1]

Problem

Often, sensors recording values of system have specification of operating range and/or minimum and maximum allowable values. For various reasons, sensor occasionally send spurious values, which are out of the range of what the sensor is physically capable of recording. We'd like to deal with these spurious values before analyzing or graphing our sensor data.

Solution

We will add a range check to all of of columns based on the upper and lower limits of the sensor:

:Aeon Multisensor Ambient temp << Range Check(LELE(-30,120));

Discussion

Here is an example of why we want to do this as part of automatic data cleanup step. It is highly unlikely that the Ambient Temp recorded by this sensor is 900 degrees. The range check is an excellent way to automatically pre-process data and also provides a measure of sensor health. Since the range check changes values to missing, you can use the Explore Missing Values platform to see if maintence is required on your network or sensor (if the sensor is sending a lot of out of range values, they will manifest themselves as missing values).

See Also

Making Sense of Sensor Data Blog Post