An invaluable feature now included with the beta software version 6.11.7 is the crank maths channel

Graphing RPM using a frequency maths channel has become invaluable when evaluating cylinder balance or confirming misfire detection reported by PCM's

In the example below the frequency maths channel formula 60/36*freq(A) is used to graph the RPM of the inductive crankshaft sensor monitoring a pick-up ring with 36 teeth (36-2) connected to channel A

Here we can graph RPM and zoom in to evaluate the acceleration and deceleration of the crankshaft (at fixed engine speeds) attributed to combustion and compression events. (All things being equal this should be uniform across all cylinders)

The missing teeth of our pick-up ring produce a momentary drop in the signal frequency seen above as the long downward spikes that consume the screen.

Whilst there is real value in the frequency maths channel, how good would it be if we could ask the software to graph the RPM but ignore the frequency drop attributed to the missing teeth of the pick-up ring?

The new crank maths channel will now do exactly that!

To create a crank maths channel, determine the number of teeth of your crankshaft pick-up ring, including the missing teeth (often 36 or 60)

Select tools, maths channel, create, next, advanced and click on crank, select the channel you require (The channel containing your crankshaft sensor) followed by a coma and the number of teeth of your pick-up ring.

Click next and select a colour for your channel, click next to name your channel and amend the scaling, and finally select finish to complete the procedure. Now tick the box adjacent to your new crank maths channel in the displayed maths channel library and select OK.

In the example below the formula looks like crank(A,36) for our inductive crankshaft sensor detecting the movement of our pick-up ring with 36 teeth (36-2 missing teeth)

The crank maths channel will now graph the crankshaft RPM and ignore the missing teeth leaving a small gap in the maths channel waveform attributed to the missing teeth. The results below speak for themselves .

There is more information about maths channels and graphing RPM here at:

The new crank maths channel will now do exactly that!

Well, not quite.

The crank maths channel will now graph the crankshaft RPM and ignore the missing teeth leaving a small gap in the maths channel waveform attributed to the missing teeth.

Sometimes along with important information you are after. It works on some captures better then others.

This feature is not ready for prime time.

I would rather it show all the information rather then hiding information. We all know when a dropout is due to a missing tooth. If this feature is going to be retained, there should be an option to turn it off and eliminate the data gaps.

Here is a CKP math channel fail.... Note that critical crankshaft acceleration information has been blanked out. Not useful in this example.

Interesting with both points. But is concerning. To download this Beta hammers my data usage and will take over an hour (Afghanistan beats my data rate).

Can someone run this through. Would like to see how it deals with it.

Thanks for that Steve.
I think there is to much of chance of setting yourself up for a fall as Tom has illustrated. Not convinced. I just can't see the benefit of removing info like that, now there is no dip. Just a blank. Sometimes even electrical noise has it's diagnostic value. Caution with filters

It's a bit like having no brussel sprouts at Christmas time. It's definitely not the best part but it's what can make the meal.

Thanks for the feedback on this - we add new features to the beta to get comments / make adjustments. Sometimes new features make it into the full release other times not.

We are not taking away the frequency option, the idea of the crank maths channel is primarily as a result of customer requests. If we remove the downward spikes due to the missing tooth / teeth then its easier to use as a RPM indicator.

Novice users get confused by the spikes and can not see the details of how engine speed is changing.

The more waveforms you give us that break the function, the easier it is for us to fix / improve.

I think it would be nice to have two options for crank. One unfiltered (with spikes) and other filtered.

We can always use frequency but then you have to know the formula. It would be easier to just input teeth count and still have option to choose what detail to see.

I can see myself using filtered crank on longer timebase when I just need reference speed. Then the line would be clearer. When I need to see each cylinder contribution then I would use unfiltered one.

It's great to be able to play with the new features in beta versions. Being able to see what users do with them often shows where adjustments or improvements are needed. This is what has helped the development team make PicoScope so great. They listen to their users.

I agree with what volrem said. The crank math function is a great idea. Makes it simple. All you have to know is how many teeth (including how many are missing). Sure, we can go back to a frequency math formula for RPM but that is easier for some users than others.

Is there anyone who had problems with the crank math function - I do have some problems with it.

I'm not able to use this simple math crank(A,60) to calculate the RPM from this crankshaft position sensor (Hall) - the next button is grayed out, so Im unable to continue the process as seen in this image.