Praneethsvch
commented
4 years ago The following is a graph which compares the solar influence on the ultrasonic readings of two sensors: The one on the left uses internal compensation only and the one on the right uses HR-Maxtemp, an additional temperature compensation which is installed outside the housing in addition to the internal compensation.
Observation:
The standard deviation of the sensor readings is larger when the HR-Maxtemp is used. Also under-compensation has been observed during the day which was not an issue when HR-Maxtemp was not used.
Further we suspect that the solar board or the wind could be contributing to the sensor's noise. Thus, the solar board has been disconnected and and a new test has been running on the battery power only, comparing the effectiveness of HR-Maxtemp.
Inside view:
The shield has been mounter carefully over the ultrasonic sensor symmetrically and sealed using liquid tape. The following is the sensor data comparing with and without HR-Maxtemp (left is without and right is with MaxTemp):
The solar influence on the Maxbotix ultrasonic sensor results in larger distance readings.
A flood captured using distance sensor is a decrease in readings when flooding followed by an increase in the readings due to evaporation. In a post-flood scenario, due to the solar influence ultrasonic might read larger distances indicating flood leaving, which is not true.
Possible solution: Using additional external Temperature compensation to negate the solar effects: HR-Maxtemp