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Automotive Problem & Oscilloscope Question

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Automotive Problem & Oscilloscope Question

Postby garrans » Fri Jul 25, 2003 5:04 am

I'm looking for a solution to a problem but have a couple of questions about oscilloscopes in general.

I have an intermittent problem with an automotive ECU. While driving the ECU shutsdown and requires the ignition to recycle. Its not the power supply (I don't think), it may be cam / crank pickups causing the problem, but I can't tell. (oh, the ECU has been replaced )

So what I THINK I need is an oscilloscope to measure signals into the ECU etc., but the problem is its intermittent.

How would I setup a unit to measure this, what would I need - What options are available (units etc.)

Also, where a given oscilloscope has a buffer size is this measured in bytes ? ie. 32K

And as such if the measurement resolution is 8 bits, can I store 32,000 entries in the DSO ?

Is this affected by the measurement cycle ie. are measurements / second fully adjustable.

Last question: What cycles would be recommended for a measurement that requires a reasonable resolution of 6 magnetic cranks sensor readings for each RPM (5500 RPM Max)
garrans
 

Re: Automotive Problem & Oscilloscope Question

Postby Autonerdz » Sat Jul 26, 2003 3:54 pm

garrans wrote:I'm looking for a solution to a problem but have a couple of questions about oscilloscopes in general.

I have an intermittent problem with an automotive ECU. While driving the ECU shutsdown and requires the ignition to recycle. Its not the power supply (I don't think), it may be cam / crank pickups causing the problem, but I can't tell. (oh, the ECU has been replaced )

Doesn't sound like a cam and crank issue to me but the scope will answer that question.

So what I THINK I need is an oscilloscope to measure signals into the ECU etc., but the problem is its intermittent.

Yup, it's the only way to look at what's going on with the signals. Here are a couple of samples from this forum:

http://www.picotech.com/support/viewtopic.php?t=48

http://www.picotech.com/support/viewtopic.php?t=77

How would I setup a unit to measure this, what would I need - What options are available (units etc.)

Pico has a very complete automotive kit which is reasonably priced and very capable. If you are in the US contact me or visit my web site. I have them in stock.

Also, where a given oscilloscope has a buffer size is this measured in bytes ? ie. 32K

The 32K buffer for the ADC 212/3, included in the automotive kit, is the amount of sample points that can me collected in a sigle pass. This buffer is shared between the two channels.

And as such if the measurement resolution is 8 bits, can I store 32,000 entries in the DSO ?

8 bit vertical resolution means 256 voltasge levels on nthe screen. The 212/3 has 12 bit resolution meaning 4096 vertical levels! This makes for fine detail.

Is this affected by the measurement cycle ie. are measurements / second fully adjustable.

The vertical resolution is affected by custom range configuration but the samples per second are affected by the time base and what you set it for. Time base is fully adjustable as well as the number of samples per pass up to 32,000. Here is another link with more depth on that:

http://www.picotech.com/support/viewtopic.php?t=287


Last question: What cycles would be recommended for a measurement that requires a reasonable resolution of 6 magnetic cranks sensor readings for each RPM (5500 RPM Max)


I would turn the samples to max and run about one second per screen. The large number of samples maintain the sample rate at long time bases and the zoom feature allows you to zoom in and examine detail scrollong back and forth through the capture.

I suggest you download the automotive demo software and play with it.


:shock:
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