I finally found some time to really look in to this 562 issue. I looked at the raw data in DataMine2 and I noticed that the 562 value appeared every 10 minutes on the minute. Then I knew that this value cannot possibly come from the sensor. I search around in my Vera device for a bit and I found some lua code that copied the "Variable1" value from the sensor to the "CurrentLevel" every 10 minutes. Then I remembered that in the previous version of this sensor the value was reported via V_VAR1 and I had to copy it to another variable in Vera to be able to draw any graph. The current version of the sensor reports the value directly to the "CurrentLevel" variable and the value 562 that was still in the old variable was copied over the "real" value every 10 minutes. I also previously had some really low values from time to time from the sensor mostly when responseHigh = 1 and responseLow = negative value so I forced the responseLow to always be a positive value like this: int responseLow = abs((int) response[3]); I will keep an eye on the behavior of the sensor now that I have finally removed the confusing 562 value.