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
Purpose of the series resistor between the TPS and the A2D?
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
Re: Purpose of the series resistor between the TPS and the A
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.
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.
If it is not understood , it will not work!
Re: Purpose of the series resistor between the TPS and the A
Thanks a ton. I figured it would be somehow related to things like that, but I wasn't sure exactly how. 
Brad
Brad