VL53L4CD Large Calibration Offsets

[will3]

Our use of the VL534LCD is within what we call a bin.  A long rectangular container.  The sensors job is to measure the distance to items placed into the bin.  Very contained environment with little interference.  

When we calibrate the sensor we do this when our bin is empty.  There is a white panel always at the beginning of the container bin which moves forward (backwards) along a track when items are placed in it or taken out.  When it is empty it is stationary at 231mm.  So,  we calibrate using 231mm.

When we calibrate to 231mm we get back offsets from the sensor > -45.  These seem unusually large to me? Why would this be?

[John_Kvam · Accepted solution]

There are 2 calibrations you need to worry about. One is offset and the other is crosstalk. 
If you have a perfect cover glass (or none at all) the crosstalk will be zero. But if you have an acceptable one you will end up ranging short. 
Read the section on crosstalk compensation in the datasheet and the user’s manual. And after finding a good crosstalk number, you will do better. 

the offset really should be less that about 2cm. but if you add crosstalk to that it can get silly. 

- john