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offline math and time reference to beginning of data

Phillip Neir

Posted on 13.04.2018 16:50

Greetings,

I want to use offline math that uses time relative to beginning of data. I have been working with a number of files where 'time' doesn't always begin at zero.

Also, there are other math variables and functions that do not start at zero at the beginning of data. This is giving me some trouble.

I have attached a sample that demonstrates what I have mentioned above.

Is there a variable that I can use that denotes the 'time' of the first datum?

Is there something I can do to have items like prev and icnt start at zero?


Attached files:
DEWESoft Support
Technical support
Posted on 23.04.2018 06:29

Hi,

I believe our new "Relative time offset" feature is exactly what you're looking for. It basically allows you to set a 0 time anywhere in the file. In your case, you can move it to the beginning of data. In the attached zip file you'll find the modified file and also a picture that shows how to access the feature.

Let me know if you'll need anything else.


Attached files:
Phillip Neir

Posted on 23.04.2018 10:40

Hello,

Thank you for your reply. I am sorry, but that is not what I need. It only seems to affect the time axis on the chart.It does not seem to affect the variable 'time'.

If you examine the digital display 'time', it is still based on the original start time of 40.785. I want to execute math based on time relative to the beginning of data. To do that, I need to subtract the time at the beginning of data. I want to build an equation "time - start_time". Is there a variable that I can access in Math that contains the start time.

Along with the previous question, is there a variable that I can access in Math that contains trigger time?

Going back to my first post, the last question I asked was about was certain Math functions that do not start at zero. If you examine the digital displays 'icnt' and 'prev' you will find that they start at 7854 and -0.7340 respectively. My question then, is there a way to set those values to zero at the beginning of data?

DEWESoft Support
Technical support
Posted on 24.04.2018 06:51

Hi,

ok, I understand what you're trying to achieve. To be honest, trying to zero certain parameters in analysis is quite a daunting task if your recording doesn't start at 0. I've managed to do this with the relative time, but I had to use the "Pre-time" parameter to do so. We don't have a trigger time parameter, but you can see that I've basically stored the trigger time value by using the hold function while looking at the trigger event.

I hope you'll be able to use this new time channel to perform further calculations. If you'll need to zero another parameter just let me know.


Attached files:
Phillip Neir

Posted on 24.04.2018 10:29

Hello,

What caused me to inquire about these items is that my data for this project has been coming from different sources. Some were triggered and some were not. I was hoping to get a system variable that was definite. Without a known start, I will have to develop two or more versions of analysis.

Your solutions are very usable and I will likely incorporate them. I appreciate your efforts. Thank you.

P.S. When you hover the mouse cursor over the left vertical grid of a recorder object, the start time appears.(ex: 40.7853Storing started) I sure was hoping to get access to that.


DEWESoft Support
Technical support
Posted on 24.04.2018 13:44

Hi,

you're welcome. Thanks for the feedback.

To be honest, I wasn't even aware that Dewesoft will show you this parameter if you however your mouse over the y axis. The only thing that's new is that you can change between an absolute and relative time format if you right click on the events list display. I though that I'd be easier to get the start time parameter, but I had a lot of trouble doing, finally resorting to the time of the trigger event. I'll try to look into this a bit more to see if we can get the start time more easily.

Kristian Erlandsson

Posted on 14.06.2019 10:22

Interesting topic. I have had the same type of problem. If I can have a suggestion for development. Include this functionality in Export. Exporting to a new Dewesoft file with a new time scale does not affect your problem with "recalculating" the database. I have used this a ouple of times by just excluding the first part of the data in th copy.The relative time will then start at zero in each copy. The problem is to get this exact moving cursors and selecting does easily lead to small errors.


By the way the description on setting a new zero in the graph relative to cursor is good but i'd love to have a possibility to set it relative to trigger.


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