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Ac Voltage Play back, HELP

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Ac Voltage Play back, HELP

Postby Guest » Fri Nov 21, 2003 6:35 pm

It has been a while since I have used the scope software.
However, maybe it's my faulty memory, I THOUGHT I was able to play back my saved data of a pico scope run of a.c. voltage while using the adc-42 to read a simple wheel speed sensor (ABS).

I gut full output on the screen, nice wavelength of positive to negative a.c. voltage, then I save to the data file format. It's been a few months, but I swear I could play back the data after the test run of voltage.

I just tried this today, and for the life of me I cannot figure out how to play back the run.
I KNOW I was able to do this before on the scope view, it's not working for me now.

I SINCERELY appreciate any advice, (yes I downloaded the latest version of the software) maybe that's my problem.

THANKs in advance!
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Postby rutger75 » Fri Nov 21, 2003 6:41 pm

Oops wasn't logged in when posting above,
also just FYI, I did also try to use the pico log software, it does not sample enough, and it did not show the a.c. waves in the graph view, it would not show anything below zero, that's a topic for a whole different forum, heh.

The end result I need, basically a datalog of exactly what the pico scope is showing me at 20 ms/div, basically not alot of voltage maybe .2-.5 range, but showing a continuous wavelengh, and periods of alternating current.

If the scope is able to show it, I can't understand why the software can't log and play it back the same way. I really need to get this working today, thanks in advance for any replies!
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Postby rutger75 » Fri Nov 21, 2003 6:59 pm

I should also state, that if I close the file, and re-open the data file, it looks like all that is saved is what was displayed on the screen, and no previous data of the run, also if I export it to text and graph it in excel, it just shows a couple wavelenghts, basically the current read-out of the pico scope and nothing more... Am I missing a data setting here?
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Postby markspencer » Mon Nov 24, 2003 8:57 am

Hi,

In Picoscope you are not able to re re-run the trace as it came in to the PC at real time, you are only able to view the trace. You can view use save on trigger to get continuous traces and then step through them one at a time.

What I think you are remembering is the Picolog Player, this is part of the Picolog recorder. Once a data capture has been run it can be viewed and played back with the player.

To sample the ac voltage and get a similar result to that of Picoscope trace you can use Picolog but will have to use the 'Fast Block Mode' this will allow you to sample as fast as the unit is capable of. However, even then you might not get exactly what you want as the ADC-42 does not have its own on board clock but dependent on the windows clock. This can be gotten around by using the USB to Parallel port adapter (only Pico's will work with this product). By using the USB to Parallel port adapter it will provide the required clocking.

Fast block mode is only intended to take a snapshot view and is best combined with triggering. However, you are unable to see the result until all the data has been taken.

Best regards,
Regards,

Mark Spencer
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Thanks for your insight...

Postby rutger75 » Wed Dec 17, 2003 6:10 pm

Thanks for the feedback, I appreciate your time.

I can't help but think the Software is my limitation on the playback of these datalogs, but I really appreciate your insight.
No offense at all, but would another software package allow playback in the format I need?

I see now that it was never logging in pico-scope.

I see what happend now, My cable was showing very low amounts of A/C Millivoltage even without spinning a tonewheel past the face of a magnetic-pickup abs wheel sensor.
When I briefly looked at the pico Scope, I thought this low voltage wavelength was data playing back from what I had just logged.
Now I realize this was some type of feeback or disturbance at Millivolts not A.C. Volts, and I had never logged anything.

Now I have a dilemna, maybe you can help.
I'm accustomed to utilizing automotive diagnostics, you just hook up to ecu diagnostic communications, and monitor 1-5 outputs from sensors, and the software saves smooth flowing line graphs for playback, albeit from Engine ECU readings. For example obd-2.com pretty cheap device and software, it just hooks up to your laptop serial port.

Based on this device, and what I read about yours, I thought this ADC-42 had more than enough sample rate to read an ABS sensor, which it does for viewing. However we need to data-log this same view, for playback in this SAME VIEW.

At the risk of overcomplicating a seemingly simple task.
I need something that will log ONE FILE for a complete trace of A/C Voltage, and I need to view the log in Oscilloscope view, saving a minute or two of data, for play back and analysis. Based on your resonse the ADC-42 is not going to do this for us, even with the USB adapter? I don't have one yet. Is the software my hold up here? Has anyone been able to use a different software package to do this?
I don't really think a time based reading is absolutely necessary, I just need to log what's there.

Even if I use the fast block mode, it just shows a brief spurt, and does not show the data in a usable format, does not show negative ac voltage values, it will not work for diagnosting faulty sensor outputs, or comparing to a known good reading. Normally you are looking for problems with smooth A.C. voltage wavelengths, the logger is not outputing the data this way.

If we could get something to work here, this could be a very BIG thing for our company. Ie, if it's portable, and relatively inexpensive, (comparaing to a hand held oscilloscope for example), we may purchase something for ALL of our field personell.


www.arvinmeritor.com
www.meritorwabco.com

As it is right now, they want to order a few more just for the Pico-scope and taking a real-time reading, however if we could get something with data-logging the same view, even just 30-60 seconds worth. We would insterested in many more units, on a MUCH larger scale, I mean MUCH MUCH larger.

So 4 questions.
Is it possible?

If not?Is the software the limiting factor?

If not?Is the hardware the limiting factor?

What are my options?

Should I post this in another forum as a "how to"
Thanks in advance.
rutger75
 

Postby ricardo » Fri Dec 19, 2003 12:12 pm

Hi,

In reply to your questions,

1.- There are two issues here, the fact that A) the software cannot sample at the high speeds you require for the lenght of time you require, and B) the software is not capable of playing back the data. I will elaborate on these two issues:

A) The ADC-42 has a maximum sampling rate of 15ksps however the software will control the sampling rate depending on the circumstances (i.e. user settings) and it will not always be able to sample at these high speeds.

With PicoScope in Chart Recorder mode, if you increase the timebase too much you will not be able to sample fast enough for ABS signals. If you use Fast Block mode you can sample fast enough at 5s/div and even 10s/div but there is so much data squashed on the screen that even with the x200 zoom you can't see the waveform properly. You would need to be able to zoom further, but at the moment this is not supported.

With PicoLog in Real Time mode you cannot sample fast enough (1ksps max) in Block mode you can sample fast enough but only for 10 seconds.

Basically the software was never designed for sampling at high speeds for long periods of time.

B) With regards to playing back data, I'm not entirely sure what you mean about this. All you can do with PicoScope and PicoLog is save the data to a file which you can reopen later for viewing.

2) The limitations in the hardware come from the fact that the ADC-42 does not have its own clock and instead it relies on the PC's clock to do the sampling. If the PC is busy doing other things (even if you move the mouse) this will affect the timing of the sampling and you might find gaps in the data, etc. One way around this is to use the USB Parallel port adatper, this device has a clock on board and takes over the timing of the sampling. Other than that the ADC-42 is fast enough and capable of logging the signal from an ABS sensor (assuming that this is not faster than 1.5kHz).


3) Your only option really is use a USB to Parallel port converter and to try and write your own software. You can download the necessary drivers from our website,

http://www.picotech.com/software.html

Having said that I can't guarantee that it will be possible to succesfully stream data at full speed for that long time (60s approx) as we have never tried this ourselves...

Best Regards,

Ric
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Thanks for your insight...

Postby rutger75 » Tue Jan 13, 2004 4:39 pm

ricardo wrote:Hi,

In reply to your questions,

B) With regards to playing back data, I'm not entirely sure what you mean about this. All you can do with PicoScope and PicoLog is save the data to a file which you can reopen later for viewing.

2) The limitations in the hardware come from the fact that the ADC-42 does not have its own clock and instead it relies on the PC's clock to do the sampling. If the PC is busy doing other things (even if you move the mouse) this will affect the timing of the sampling and you might find gaps in the data, etc. One way around this is to use the USB Parallel port adatper, this device has a clock on board and takes over the timing of the sampling. Other than that the ADC-42 is fast enough and capable of logging the signal from an ABS sensor (assuming that this is not faster than 1.5kHz).


3) Your only option really is use a USB to Parallel port converter and to try and write your own software. You can download the necessary drivers from our website,

http://www.picotech.com/software.html

Having said that I can't guarantee that it will be possible to succesfully stream data at full speed for that long time (60s approx) as we have never tried this ourselves...

Best Regards,

Ric


Happy New Year, and thanks so much for the quick reply.

1)
B)
I mispoke myself when I said playback, I meant reviewing the data on a graph, which I could even do by graphing in excel, but there is not enough data there, even for short spurts in fast block mode, it doesn't seem to wan't to output negative values in the softwares graphing mode either.
Thanks for the explanation their.

2) 1.5 khz should be more than fast enough sampling.....

I understand the limitations of having no seperate timing on a circuit board, and the fact that the Pc's processing speed may fluctuate and affect timing. I agree it would be better to have external timing. Having said that, this hardware limitation of the ADC-42 does not seem to affect the Pico-scope view that has been used thus far, and we are satisfied with the outputs thus far.
I guess my assumption is that if using "Pico-scope"; I can view the full A/C voltage wavelength from peak positive and peak negative all the way through, repeating over and over, then I assume there is no hardware limitation, being that I'm able to see this smooth wavelength outputted by the software's "scope view" on my pc's screen.

So my two options are to go with a parallel>usb adapter, or assemble my own pcb circuit with timing control.

3) I hate to purchase a usb adapter, only to find out I still have hardware limitations, that's why I asked.
My interpretation of your response is that after the timing issue is resolved, and of course assuming less than 1.5 kHz sampling, the software is my only limitation for logging this data for 25-35 seconds?.

This is of course excluding any PC limitations that 2.2 Ghz P4 512mb laptop would offer(which I don't think would be a problem).

I said 60 seconds as a guestimate, but really 25-35 seconds would certainly be enough time to get a comparison reading, and would be acceptable time interval to get repeat samples.

Thanks again for your explanations, and thanks for providing those drivers.
I think this is actually a good opportunity, and forces us tailor a software to our needs. I think I would rather compile or write a software that could analyze two or more runs for playback or graphing, overlayed for comparison.

Thanks in advance for your insight on my last questions here,

-Don
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Postby markspencer » Wed Jan 14, 2004 8:40 am

Hi,

Thank you for your post. In Picolog you can see the negative and positive peak. You may have to manipulate the graph with the vertical zoom in and zoom out or up and down the buttons these can be found on the right side of the graph.

This is also true in Picoscope it will automatically show the ±FSD range. Assuming that the appropriate timebase is choosen, which takes minimum 5 sample per cycle, preferably 8 samples per cycle then the waveform should be relatively smooth.

I would advise that you purchase our USB to parallel port adapter, as no information can be release on the parallel port Pins.

The USB adapter, will not allow the unit to sample faster, it will provide the ADC-42 an independence from the operating system and thus provide a distinct/exact time interval between samples.

The software limitation will still apply with only 10 seconds being available window to get data in fast block mode. However, this can be gotten around if you did write your own software, as you suggested.

Best regards,
Regards,

Mark Spencer
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