Comparing the sensors.

    The orion rain sensor was replaced on 11may21  with a spare sent from orion. Rain data from 12may21 through 06feb22 was used to compare the rain sensor with the orion tipping bucket. Both of these devices are installed on the orion system located on  the lidar lab roof. They are read simultaneously.

    Data is read from the orion system every 15 seconds. It includes data from the rain sensor and the tipping bucket. The  rainToday(2) values was used to compare the 2 devices. The maximum value from each day was used as the daily rainfall. Data from 12may21 through 06feb22 was used: 270 days. 5 days were excluded because of bad readings (mainly power outages). This left us with 265 days of data.

    The plots compare the results from the 2 sensors (.ps) (.pdf)

• Top: over plot rain sensor and tipping bucket
• black is the rain sensor
• red is the tipping bucket
• the horizontal axis is date: yymmdd_hh
• the vertical axis is the daily rainfall in inches.
• The totals for each device (265 days) is also printed:
• rain sensor: 38.3 inches
• tipping bucket: 47.1
• This is a 25% difference (47.1-38.3)/38.3
• Middle: tipping bucket - rain sensor
• the daily difference is  plotted vs  date.
• most of the differences are > 0 ( the tipping bucket value is  > than the rain sensor value).
• Bottom: measured differences vs daily rainfall
• The vertical axis is the daily difference (Tipping bucket - rainSensor) in inches of rain
• the horizontal axis is the daily rainfall (taken from the rain sensor).
• As the daily rainfall increases there is an increase in the difference,

SUMMARY:

• 265 days of rainfall data was used to compare the values from the rainfall sensor and the tipping bucket.
• The totals for the 265 days were:
• tipping bucket: 47.1 inches
• rain sensor     :38.3 inches
• this is about a 25% difference.
• Most of the differences were positive (the tipping bucket value was greater than the rain sensor).
• We saw similar differences when comparing the pre may21 rain sensor with the tipping bucket (more info)

processing: x101/wst/test/compare_sensors_may21_feb22.pro

home_~phil