How to separate samples I/0 signal?

[08anja]

Hi people, 

I got a signal which is high in ~10ms and low in ~1ms. I'm only interessed in the samples that are in the high state. 

I tried with the Waveform Get Subset DBL but without any luck. Is there another way or did i just misunderstood the values start sample and duration?

Thanks in advance

[GerdW]

Hi anja,

try something like this:

Using conditional tunnels in more recent LabVIEW versions will simplify this snippet image even more!

[08anja]

Hi GerdW

Thanks for the fast reply. 

It looks like it would work. I supposed that you look at the values and apply greater than 2. But I have one issue that my signal can vary all the way down to 0.5 V at the high state. (it depends on which surface i place my sensor on). 

So i guess I needed it to be calculate on the time the signal is high? 

[GerdW]

Hi anja,

you could change the comparison to compare with "minimum of the measured signal plus a small offset"…

[08anja]

Yeaah.. but in some case my signal can look like this and I'm not certain of with offset i should use beacuse the varied signal. The one thing im certain about is the time when it high and low, so i would look it to depend on that? Any good ideas? 🙂 

[GerdW]

Hi anja,

your LOW signal seems to stay below 0.05. I still would prefer a simple comparison!

Why make things more complicated than they are?

[08anja]

Yeah, but a third scenarie, agian I can place my sensor different places which gives different input. 

Here is my low signal ~1,75. So as you can see the low periode can vary alot. But yes I would like to use a simple comparison, but I dont think it would work en generally if do not depend it on the time? 

[GerdW]

Hi anja,

some messages before I wrote "minimum of signal + offset"!

So you could get the minimum of the signal (~1.75), add 0.1 as offset to get a comparison level of ~1.85.

To reduce the noise I would adapt a running average over some samples…

[08anja]

Hi GerdW

Okay, Im getting to see what you mean. Could you show me hoe to implement the small offset to the minimum? 

I would surely do it as simple as I can, but do you have any ideas how to control it by the time? 

//Anja