Having troubles with my parallax usb oscilloscope ...
turbosupra
Posts: 1,088
Since there is no forum for the usb oscilloscope, I posted this here, since some of the tutorials include using the basic stamp with the oscope.
In trying to use this oscope, I've never had it perform the way that I expect it to
It always gives you 1500 lines of values/log from the view --> export data to file, even if you aren't sampling for a time of the horizontal setting value * 1500, why is this?
Sometimes I see a min and max voltage of different values then it outputs in the text file you can save?
Tonight I sampled values from a 9v battery, in the first sample I pulled the probe off and then put it back on, which it reflected in the log/text file (albeit at the wrong timing location in that file)
Then I resampled from the same 9v battery, this time I did not pull the probe off, just let it sample for 3 seconds. I then exported the log file(from the view --> export data to file), and it showed the same EXACT log settings (including the voltage drop to 0.00v in the same EXACT locations as the previous test), although it should have just shown a straight 9v through all 1500 lines of sampling values.
I can't tell in the instructions, if you have to set the trigger for the channel you are using, to a value that is lower than your minimum voltage, or higher?
Even at a 1s horizontal sampling rate value, I'm getting 1500 lines of log from the view --> export data to file, even when I am only logging for 5 seconds? Why am I not getting 5 lines of log files from the view --> export data to file function?
Having 1500 lines when I should have 5 makes it pretty confusing, especially when you have log files from the view --> export data to file that are not changing when the input values are, and when the timing representation settings are also not seemingly accurate?
Help please
In trying to use this oscope, I've never had it perform the way that I expect it to
It always gives you 1500 lines of values/log from the view --> export data to file, even if you aren't sampling for a time of the horizontal setting value * 1500, why is this?
Sometimes I see a min and max voltage of different values then it outputs in the text file you can save?
Tonight I sampled values from a 9v battery, in the first sample I pulled the probe off and then put it back on, which it reflected in the log/text file (albeit at the wrong timing location in that file)
Then I resampled from the same 9v battery, this time I did not pull the probe off, just let it sample for 3 seconds. I then exported the log file(from the view --> export data to file), and it showed the same EXACT log settings (including the voltage drop to 0.00v in the same EXACT locations as the previous test), although it should have just shown a straight 9v through all 1500 lines of sampling values.
I can't tell in the instructions, if you have to set the trigger for the channel you are using, to a value that is lower than your minimum voltage, or higher?
Even at a 1s horizontal sampling rate value, I'm getting 1500 lines of log from the view --> export data to file, even when I am only logging for 5 seconds? Why am I not getting 5 lines of log files from the view --> export data to file function?
Having 1500 lines when I should have 5 makes it pretty confusing, especially when you have log files from the view --> export data to file that are not changing when the input values are, and when the timing representation settings are also not seemingly accurate?
Help please
Comments
I’m not sure what is happening with your min/max voltages, but the output file will always be 1500 lines because it always outputs the entire buffer contents, even if it hasn’t all been used. The buffer size is fixed and cannot record any more than the max samples you see.
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Chris Savage
Parallax Engineering
50 72 6F 6A 65 63 74 20 53 69 74 65
·
How do I troubleshoot this?
What are the buffer contents, how do I clear them, and if there are only 100 new inputs to the buffer contents, where are the other 1400 lines of data drawn from?
Does it work so that you have have 1500 lines total (1 being the newest and 1500 being the oldest), and a new entry/value is taken by the oscope, does it just delete the oldest value and then push the remaining values down one "line" and then write the most recent value to line 1? And repeat this process each time it samples/records a value.
For example, the oscope is setup to record a value each second, and has previously recorded a steady 12v for hours and then you connect the oscope to a 9v battery and keep it set to record a value each second? Like what I've put below, is that correct?
Before the first measurement
1 - 12v
2 - 12v
3 - 12v
4 - 12v
5 - 12v
6 - 12v
7 - 12v
8 - 12v
9 - 12v
10 - 12v
11-1500 - 12v
After the 1st measurement/1st second
1 - 9v
2 - 12v
3 - 12v
4 - 12v
5 - 12v
6 - 12v
7 - 12v
8 - 12v
9 - 12v
10 - 12v
11-1500 - 12v
After the 2nd measurement/2nd second
1 - 9v
2 - 9v
3 - 12v
4 - 12v
5 - 12v
6 - 12v
7 - 12v
8 - 12v
9 - 12v
10 - 12v
11-1500 - 12v
After the 3rd measurement/3rd second
1 - 9v
2 - 9v
3 - 9v
4 - 12v
5 - 12v
6 - 12v
7 - 12v
8 - 12v
9 - 12v
10 - 12v
11-1500 - 12v
After the 4th measurement/4th second
1 - 9v
2 - 9v
3 - 9v
4 - 9v
5 - 12v
6 - 12v
7 - 12v
8 - 12v
9 - 12v
10 - 12v
11-1500 - 12v
After the 5th measurement/5th second
1 - 9v
2 - 9v
3 - 9v
4 - 9v
5 - 9v
6 - 12v
7 - 12v
8 - 12v
9 - 12v
10 - 12v
11-1500 - 12v
After the 6th measurement/6th second
1 - 9v
2 - 9v
3 - 9v
4 - 9v
5 - 9v
6 - 9v
7 - 12v
8 - 12v
9 - 12v
10 - 12v
11-1500 - 12v
After the 7th measurement/7th second
1 - 9v
2 - 9v
3 - 9v
4 - 9v
5 - 9v
6 - 9v
7 - 9v
8 - 12v
9 - 12v
10 - 12v
11-1500 - 12v
After the 8th measurement/8th second
1 - 9v
2 - 9v
3 - 9v
4 - 9v
5 - 9v
6 - 9v
7 - 9v
8 - 9v
9 - 12v
10 - 12v
11-1500 - 12v
After the 9th measurement/9th second
1 - 9v
2 - 9v
3 - 9v
4 - 9v
5 - 9v
6 - 9v
7 - 9v
8 - 9v
9 - 9v
10 - 12v
11-1500 - 12v
After the 10th measurement/10th second
1 - 9v
2 - 9v
3 - 9v
4 - 9v
5 - 9v
6 - 9v
7 - 9v
8 - 9v
9 - 9v
10 - 9v
11-1500 - 12v
etc etc ....
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Chris Savage
Parallax Engineering
50 72 6F 6A 65 63 74 20 53 69 74 65
·
So it's a round robin with the ram/cache?
Is my example correct on how it fills the cache?
I've also noticed in my log txt files
When you choose the horizontal setting in software version 5.1 of 50us, the log file says "Sample Rate: 1M/s"
When you choose the horizontal setting in software version 5.1 of 100us, the log file says "Sample Rate: 500KS/s"
When you choose the horizontal setting in software version 5.1 of 200us, the log file says "Sample Rate: 250KS/s"
When you choose the horizontal setting in software version 5.1 of 500us, the log file says "Sample Rate: 100KS/s"
When you choose the horizontal setting in software version 5.1 of 1ms, the log file says "Sample Rate: 50KS/s"
When you choose the horizontal setting in software version 5.1 of 2ms, the log file says "Sample Rate: 25KS/s"
When you choose the horizontal setting in software version 5.1 of 5ms, the log file says "Sample Rate: 10KS/s"
When you choose the horizontal setting in software version 5.1 of 10ms, the log file says "Sample Rate: 5KS/s"
When you choose the horizontal setting in software version 5.1 of 20ms, the log file says "Sample Rate: 2.5KS/s"
When you choose the horizontal setting in software version 5.1 of 50ms, the log file says "Sample Rate: 1KS/s"
When you choose the horizontal setting in software version 5.1 of 100ms, the log file says "Sample Rate: 500S/s"
When you choose the horizontal setting in software version 5.1 of 200ms, the log file says "Sample Rate: 250S/s"
When you choose the horizontal setting in software version 5.1 of 500ms, the log file says "Sample Rate: 100S/s"
When you choose the horizontal setting in software version 5.1 of 1s, the log file says "Sample Rate: 50S/s"
So even at the horizontal setting of 1s, it samples at a rate of 50 samples per second?
Also, why is there a delay in what the automeasurements screen from when you click run, to when it starts showing voltage values?
Thanks for reading
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Chris Savage
Parallax Engineering
50 72 6F 6A 65 63 74 20 53 69 74 65
·
And if it's anything more than 20ms, it's going to take at least ~2 seconds or more for that buffer to fill.
Has anyone written software to use the usb driver to log any better? Is the buffer a hardware or software limitation?