Switch

Can i ground my switch to the chassis instead of ecu ground or sen 0v,does it have some drawbacks

That will depend on the device. Usually best practice is to use the correct 0V pin for the signal pin.

I have recently been fighting sensor values from resistive type sensors on a car in Thailand that I'm helping with. It seems there is a bit of a ground offset between the dash ground and the engine ground, this shows up as a voltage differential causing sensor calibration to not be correct. However, the OEM sensors / wiring did not have a separate ground, and we are forced to live with slightly wrong readings.

Do the best thing -- use the correct 0V.

thank you so much david.do i need to match sen5/0 V for the digital input and how do i know which digital pin's pull up use which sen 5v(a,b,c)(i can't find information from m150 datasheet)or ecu power ground should be fine.btw what is the project in thailand you are helping recenly.mine is formula student,its my first project so i have question a lot and the forum helping me very much

does this considered to be star point earthing? or should i ground my ecu to engine ground to prevent ground offset from ign trigger system.

Yes, that ground plan will be OK. For an M150, you can use any of the 0V for a digital input. If you were using a Temperature Input, there is a specific voltage reference (0V pin) listed in the help for each Temperature Pin.

My recent Thailand project was installation of a MoTeC C1212 into a Jaguar XJ220 prototype. We duplicated the original factory gauges in Display Creator. Turbo engine is running on an M800.

thank you so much david this forum helps me a lot.never regret joining hpa