save on trigger

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save on trigger

Postby alexchong@clear.net.nz » Thu Mar 27, 2003 10:19 am

if i scope a 4 cylinder ignition and it's set to save on trigger then i should of saved 2000 files at 1000rpm correct?
is the adc 200 fast enough to do this?
Mybe i've got my scope options wrong?
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Postby matthew » Thu Mar 27, 2003 2:18 pm

Hi,

There's no way that the ADC-212 or the PC could write files at this speed, It would take a very long time to sift through 2000 files anyway (half an hour when viewing 1 file per second), so there would be little point in collecting this amount of data.

Best Regards,
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Postby Autonerdz » Thu Mar 27, 2003 10:05 pm

How fast you save files using 'save on trigger' is largely dependent on how high you have the samples turned up. Larger blocks of data slow the screen update. Here is a blurb on the sublect from my Pico Forum:

The "Save On Trigger" function is a vert powerful feature when trying to capture that elusive event.

Here are some tips about this feature for everyone:

Ever wished that you had captured that thing that just happened on your screen? If you use the "Save On trigger" option, you already did. Pico will write each triggered capture to the hard drive.

Select this feature from the "Settings" - "Trigger" dialog box.

Caution: It will save them all the last place a file was saved to. So, to avoid making a mess and so you can find where they went, make a special file for a run of these and save the first one using the "File" - "Save As" selection and direct it to that special location. Now they will all go there.

The default number of captures is 100. This is for your protection so you don't fill your hard drive with endless captures. These are not seamless captures but snapshots like from a motor drive camera.

If you desire more than 100 captures, you can increase it to any desired amount. You set the limit. The procedure is a bit clunky and requires you to edit an ini file, but here is what I suggest:

The default installation writes a section in the file "Win.ini" headed "[PicoScope for Windows]". The "Win.ini" file is located in the Windows directory. The settings are stored here. Ok, it scares me to edit a file like this with so many other things in it that affect my system. So, open the "Win.ini" file with Notepad and just copy the "[PicoScope for Windows]" section. Now close the "Win.ini" file making no changes. Now paste what you copied into Notepad and save as "PSW.ini" into yout main Pico folder. Pico will now use this file instead of the "Win.ini".

Now you can edit it and if you totally botch it you can just delete it and do over, not scary now :-) Now add this line:

"MaxSOTFiles=X" where "x" is the maximum number of files you want written to the drive during a save on trigger session. Save the file to the Pico folder as "PSW.ini" This should be automatic since you should have just saved it to begin with. Now, whenever you want to change the limit, just open the file change the number and save. That's it. I know, it seems like a pain but you only have to do all this once. Then it's simple. You just edit the "PSW.ini" in your Pico folder.

All this is in the Pico documentation under "Trigger Dialog".

Now you can start and stop the scope with the space bar, you don't have to watch the screen. You can watch the road. :-) Each screen, up the the limit, will be saved and you can review them later, stepping through them all with the "page up" and "page down" keys on the computer.

Now you can save thousands of screens if you desire. Just try to do that with brand x.

:shock:
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Postby matthew » Fri Mar 28, 2003 10:24 am

Thanks for the input Tom,

I'd forgotten that Alex may not have his trigger limit uncapped. To extend the first point you brought up (the amount of data collected per save). You can change this from: Settings|Options|Advanced reduce the value of the 'Number of Sample per Scope Trace' (this can go down to 500 ... but you'll lose a lot of detail from the trace).

Best Regards,
Last edited by matthew on Wed Apr 23, 2003 7:20 am, edited 1 time in total.
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Postby Guest » Wed Apr 02, 2003 9:19 am

point was to save everything and then delete my saved folder
:idea: Hate having a car miss-firing in front of a peice of test gear and unable to capture a bad pattern to analyse it
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Postby alex » Tue Apr 22, 2003 9:49 am

DAMN IT!! it's happened again today, car miss firing and when i review what i saved, i can't find it.
Wheeled out my old crt scope and i can clearly see double firing and gaps where the ignitor failed to fire
Maybe i should set the X line to 1ms X 100 ? and catch one big long piture?
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Postby matthew » Tue Apr 22, 2003 10:27 am

Alex,

The scope doesn't capture one big picture unless you ask it to (as per your suggestion) ... so you were probably just unlucky that the car was misfiring during the gaps in your data. If you capture a long run of data, you have to bear in mind that the units onboard memory is finite, and you may not get the required number of samples for a clear picture over a long period of time.

The other way to approach this is to minimise the gaps in the data by collecting less data. Reduce the number of samples per scope trace as per the instructions in a previous post in this thread. This won't guarantee that the data is captured but it may help.

Best Regards,
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Postby Autonerdz » Tue Apr 22, 2003 7:45 pm

alex wrote:DAMN IT!! it's happened again today, car miss firing and when i review what i saved, i can't find it.
Wheeled out my old crt scope and i can clearly see double firing and gaps where the ignitor failed to fire
Maybe i should set the X line to 1ms X 100 ? and catch one big long piture?


Unfortunately, there are gaps between the screens which may cause you to miss something. I usually do run longer time per division captures and maybe put a second on the screen then zoom in and examine it. If you do this, be sure to set it in Block Mode under Settings-Options-Advanced. If you run more than 100ms/div in anything other than Block Mode your sample rate will be very poor (1K/sec).

As Matt mentioned, the sample rate will be affected by time base. Here is how you can get an idea:

Take the number of samples collected (what you set it for) and divide by the time of the capture in miliseconds. The result will be your requested sample rate in KHZ.

The available sample rates are divisible by two starting with the max speed. The fastest is 3000khz and the next step is 1500khz then 750khz etc. If the requested sample rate falls between the available rates, the next slower step is selected.

Now, if you want to find the number of points for a certain event, multiply the event time by the samples per second rate. You need at least 5-10 samples to reliably reconstruct an event.

For example:

I set my time base at 100ms/div and my samples maxed out at 32,000 in Block Mode. My requested sample rate is 32,000 s/sec. (32,000/1000ms = 32khz)

The scope will then choose the 23.437 khz speed. At this rate, during that one second screen, I will reliably see events as small as 250us. (23,437 x .00025 = 5.86 samples) 250 millionths of a second isn't bad :-)

Half the sample rates if using both channels.

I know, it's a brain teaser but if you play with this you will have a much better understanding of the instruments capabilities and limitations. Then you will be able to be more effective. Besides, it's fun :-)

:shock:
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Postby Guest » Sun May 11, 2003 9:30 am

don't supose anyone has figured a way to say save up to 500 files then automactically start overwriting them?
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Postby markspencer » Mon May 12, 2003 8:01 am

Hi,

The only way to automatically save a file in Picoscope is to use "Save On Trigger" from Settings|Trigger.

It is not possible to set a number of files and then overwrite them automatically. However you can set the number by editing the appropriate section of the C:\WINDOWS\win.ini - ie:

Code: Select all
[PicoScope]
MaxSOTFiles=500

Best regards,
Regards,

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