SEN0642 UV Sensor - Reporting Bad UV Index
LarryWilhite 2026-08-14 00:40:15 150 Views2 Replies SEN0642: UV Sensor
Modbus communication is good, the sensor reports a UV Index of 15 for any Intensity reading above 3.6 (360 Raw)?
An Intensity of 2.5, reports UV Index of 10?
Any ideas why the Index is incorrect?
SEN0640: Irradiance Sensor
Modbus communication is good, but at ~1250 w/m2, comparing to my calibrated Fluke meter, the SEN0640 is ~200 w/m2 high?
SEN0640: there's a calibration offset register at 0x0052. Write 200 to it (function code 0x06) and the readings should line up with your Fluke. Range is 0–1800.
SEN0642: the UV Index is cooked up internally from the Intensity value, and there's no separate calibration for it — only the Intensity has an offset register. The jump from 10 to 15 and the hard cap at 15 smells like a firmware bug in the lookup table, not a calibration drift. Your best bet is to ignore the built-in UV Index, read the raw Intensity, and calculate the index yourself from the sensor datasheet curve. Or ping DFRobot support — this one's on their firmware.
Jason.Miao Thanks,
I'll try utilizing the offset register on the SEN0640.
Agree the SEN0642 is acting like a software bug. I'll find the datasheet.
