Light Sensor Lux Variance

I have been meaning to add light sensors into my smarthome for a while, and have been looking at different devices. I find the Lux levels they report vary differently.
At the moment I have my 3 sensors sat on the same table in sunlight and they report
Neo Coolcam Motion Sensor: 2266 Lux
Hue Motion Sensor: 109 Lux
Aeon Multisensor 6: 46 Lux

Is this common?
Do I need to calibrate them somehow?
Or do I just accept it and treat each device as its own thing?

I have two Aeon 6’s sat next to each other in indirect sunlight. One reads 166 and the other reads 33. Go figure...

I suspect some light meters are designed to show whether the light is either on or off rather than giving accurate measurements of light intensity.

Since you tested your meters in direct sunlight through a window, I suspect the reading from the Neo sensor is closest to being correct. Even it might be low, depending upon the time of day and cloud conditions.

One Lux is the amount of light cast by 1 Lumen across a 1 square meter area. It is the light of a single candle. A typical 60 watt incandescent lightbulb is approximately 800 lumens, Even on a cloudy day, sunlight is going to be several times that value. However, many windows are designed to absorb some light frequencies, so that could affect your readings.