Graphing PWM and Duty Cycle

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Graphing PWM and Duty Cycle

Postby samjesse » Fri Feb 08, 2013 5:09 pm

Hello
using 4000 hardware with 6.7.11.1
Is there a video or written instructions on how to graph PWM and duty cycle "of say an injector"? if not, how can it be done?

Thanks
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Re: Graphing PWM and Duty Cycle

Postby bhagedorn » Thu Feb 14, 2013 6:12 pm

Excellent question. I want to know too. Somebody need to publish a book titled "Pico for Dummies." I will certainly be the first person to buy it.
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Re: Graphing PWM and Duty Cycle

Postby samjesse » Thu Feb 14, 2013 8:48 pm

Pico can graph frequency, it can measure and post "in a text box" the Duty Cycle (under Measurements). Sure it is not too far fetched to capture and graph streaming Duty Cycle, I am at lose as to why it "and PWM" have not be implemented yet. Other scopes "used in the automotive field" graph both.
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Re: Graphing PWM and Duty Cycle

Postby samjesse » Thu Feb 14, 2013 10:14 pm

bhagedorn wrote:Excellent question. I want to know too. Somebody need to publish a book titled "Pico for Dummies." I will certainly be the first person to buy it.


No pico for Dummies yet, but meanwhile it is well worth it to take a look here http://www.autonerdz.com/cgi/yabb2/YaBB.pl?board=picopub
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Re: Graphing PWM and Duty Cycle

Postby pjaska » Wed Oct 30, 2013 4:20 pm

Hello! i would also be interested to know how to graph PWM and duty cycle. I tryed messing around with the math channels but im not so brilliant with that stuff :oops: would also like to know if there is any good info anywhere about how to use math channels?
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Re: Graphing PWM and Duty Cycle

Postby Fat Freddy » Thu Oct 31, 2013 2:27 am

I too would like to see this as PWM/Duty cycle is a very large part of engine management today.

Let's hope it is implemented in the software sooner rather than later. :)

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Re: Graphing PWM and Duty Cycle

Postby arjen » Thu Oct 31, 2013 9:06 pm

I agree, it would be very usefull to graph pwm signals.
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Re: Graphing PWM and Duty Cycle

Postby Steve Smith » Fri Nov 08, 2013 2:36 pm

Sorry this replay is late, but the questions raised are very interesting and well worth following through

Measuring duty cycle can be carried out at specific point during a captured trace by selecting MEASUREMENT tab ADD MEASUREMENTS-select which channel you need to measure e.g. A-select measurement type DUTY CYCLE then select BETWEEN RULERS then click OK.
Now drag your time rulers onto your duty cycle capture where you wish to measure the duty cycle, the “duty cycle measurement bar” at the bottom of the scope screen will now display the duty cycle at any point along your capture dependent on where you place your time rulers.
You can also lock your time rulers to enable you to drag both time rulers together at the same time which is useful if you are measuring similar portions of your duty cycle capture. This can be actioned by clicking on the pad lock symbol located inside the “Ruler Legend”

Graphing PWM and Duty cycle most certainly is a valuable feature and can be utilised with the Pico 4223 or 4423 automotive oscilloscopes. I have attached a capture taken from the IMV (Inlet metering valve) control signal of a Mondeo 2.0TDC-I from idle speed to WOT and return to idle. The connection to the IMV signal wire is identical to the pre-set menu under the automotive tab for MAF DIGITAL testing. Using Channel A to measure the voltage signal and Channel B to measure the same voltage signal but using the frequency option you can see the effects on IMV duty control by reviewing the trace captured on Channel B.

Once again I hope this is of some help, take care……Steve
Attachments
2002 MONDEO 2.0 TDC-i-IMV DUTY OVER FREQUENCY20131108-0001.psdata
(755.85 KiB) Downloaded 241 times
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Re: Graphing PWM and Duty Cycle

Postby Robski » Fri Nov 08, 2013 8:45 pm

the “duty cycle measurement bar” at the bottom of the scope screen will now display the duty cycle at any point along your capture dependent on where you place your time rulers.

'High' time yes.........perfect for pull up design :wink: (yes i know the ways round it before anyone mentions, i am making a point to the not so aware)

I'm not sure what use the channel with frequency is apart from a drop out in signal maybe ? similar to an RPM math channel.

The duty cycle graph what is being requested is to quickly see via a linear graph the duty cycle not the frequency of the wave.
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Re: Graphing PWM and Duty Cycle

Postby Fat Freddy » Sat Nov 09, 2013 6:45 am

Measuring duty cycle can be carried out at specific point during a captured trace by selecting MEASUREMENT tab ADD MEASUREMENTS-select which channel you need to measure e.g. A-select measurement type DUTY CYCLE then select BETWEEN RULERS then click OK.


It's the graphing capability that is missing. Looking for glitch's with rulers isn't really ideal and rulers do not show how it fits in the bigger picture. Duty cycle is as important as volts and amps in todays technology, if not more so.
I would think it's well with in Pico's capability's to implement it. :wink:

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