s4c wrote:Please have a look at the attached post. If you could work it out it would be great. Also, if you could show me the workings for future ref that would also be great.
As everyone points out correctly, your sample rate is way too low - you should be sampling at no more than 25us for looking at these sorts of frequencies (20Hz to 2000Hz). The method Robski was using is the only option open to you, i.e use the cursors to measure the period. To get a direct frequency measure, you will need to add a measurement on channel B, set it to "Freq" and set it to measure the range between the cursors. That will give you some idea of the frequencies that you are seeing, if you span a couple of cycles with your cursors.
There is enough data to see that you have an airflow oscillation when the TPS is opened, and it doesn't seem to attenuate towards the end of the TPS = 5v part of the trace. So you need to measure again, maybe add a channel for engine speed (one coil primary input would give you a rough speed indication for 720degs CA) at a better rate. I think that you have a valve sticking problem, but without an engine speed, you have got nothing to divide the airflow by, and that is assuming you can scale frequency to airflow.... You might just be seeing a signal drop-out on the MAF meter, but with your present sampling, who can say?