MSefi.com read only forum (Jan.15,2018)

Could someone tell me the purpose of the 1K resistor between the Throttle Position Sensor input and the A2D on the micro? (R9 on MegaSquirt V3)

I'm just asking out of engineering interest, but I'd be really interested to know the answer.

Thanks,

Brad

The main function is to create a Low Pass filter together with the capacitor that is conected to ground.. High frequency disturbances will be attenuated and thus not influence the AD reading. A second less obvious function is to limit the input current at input overvoltages into the MS. Each ADchannel chip input has a voltage clamp internal circuit ( At least on the MS1 processor) that offers some protection against incoming overvoltages that are not overly severe. And , yes , I have of course tested that by discharging a capacitor of 25 µF charged to 15 V into a typical AD input thru the input resistor. No damage done. Tried directly onto the AD input and the AD channel checked out!

Heribert.

Thanks a ton. I figured it would be somehow related to things like that, but I wasn't sure exactly how.

Brad