Issue with data "resolution"

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RobF
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Joined: Wed Jul 06, 2016 5:42 pm

Issue with data "resolution"

Post by RobF » Wed Jul 06, 2016 6:01 pm

Hi,

I bought a PicoScope 2204A for a university project involving testing solar panels to replace a dated XY plotter. My measuring runs do generally work as intended but when I import the provided data to Excel and create the desired graphs I get very jagged lines instead of smooth curves:

Image
or
Image

Taking a look at the values I can see the problem but I have no idea how to fix it or what settings I have to change:

Image

For both channels there seem to be rather distinct "steps" with few alternating values instead of a smooth transition. My intuition would to increase the "resolution" of the data, but... well, I hope you can point me in the right direction :D

bennog
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Location: Netherlands

Re: Issue with data "resolution"

Post by bennog » Sun Jul 10, 2016 7:58 am

start by setting the vertical resolution to +/- 2V or even +/- 1V (don't use the auto value), it looks like it is set to +/- 10V at the moment.
Looking at the sample interval you about 30 samples / second you can also enable resolution enhancement to 12 bits.

Benno

Gerry
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Joined: Mon Aug 11, 2014 11:14 am

Re: Issue with data "resolution"

Post by Gerry » Thu Jul 14, 2016 11:15 am

Hi RobF,

Bennog is correct in saying you shouldn't use auto-ranging for your capture, because when you are sampling as slow as 30S/s PicoScope 6 won't have enough data, soon enough to choose a suitable range. It looks as if the problem is resolution in amplitude, because the graphs are limited to just 4-bits of data (in some cases less). What you need to do is set the input range on the channels to just larger than the largest +ve or -ve value that you are likely to get on any channel.
Looking at the actual data you have less than 100mV, more than -100mV on channel A, and less than 1V on Channel B. So, it looks like you need to set the input ranges to +/-100mV for channel A, and +/-1V for channel B. Unfortunately though, Enhanced Resolution Mode won't help because it is only applied to the image on the screen, not the data in the buffer that you export.

Also, to make the graph smoother, it's possible that you may need to increase the sample rate. As you're trying to replace your chart recorder, I'm assuming that you need to log the data for a fixed amount of time - which means that you can't change the collection time, i.e.timebase. However, you could use our PicoLog software, in Streaming mode to increase the sample rate of your data up to as fast as 1,000 samples per second, and save up to 500,000 samples at your current collection time of 8m20s. PicoLog will also export CSV, and is better suited to data logging applications such as this.

Regards,

Gerry
Gerry
Technical Specialist

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