Feature request: Allow Offline math on reduced / slow data

Currently there is a limitation that "Offline math will not be available on reduced data" when using the "always slow" or "fast on trigger, slow otherwise" storing types. It would be useful to be able to use offline math on slow data.

Dear Matt,

thank you for reaching out to us.

Unfortunately, using offline math on slow data cannot be implemented.

During a slow storing of data, DewesoftX acquires the data with full speed and then calculates the minimum, maximum, average and RMS values. The only data that is stored are the MIN, MAX, AVE, RMS values for the duration of the static acquisition rate.

Offline math can only be used on fast stored data. 

If there's a particular Offline stored data around the trigger you would like to work with, you can use the Pre- and Post- trigger time. You can read more about it here.

The other option would be to measure all data as fast, and store only the channels that are relevant for you. You can read more about this option here.

Would either option work for you, or do you have a specific application you would like to use this with?

Best regards,

Pika

Thanks for the reply.

I'm using slow storing because I have a lot of channels and the file size is excessive even when doing slow storing and occasionally doing 2 second long fast triggers. I've already optimized the file size by only storing important channels. Other channels are set to Used, Not Stored.

I understand that offline math would be complicated if the slow data is stored as MIN, MAX, AVE and RMS within a single channel. I'd like to see DEWESoft give the user control on how slow data is stored / displayed: Allow the user to pick if slow data is stored as MIN, MAX, AVE, and/or RMS. And if the slow data is only one type of value (e.g AVE) then I'm assuming offline math would be feasible (and my feature request could be implemented).

Thanks
Matt

Dear Matt,

I gather you wish to reduce the size of the recorded datafile. Could you please elaborate ''the file size is excessive'' further? What do you mean by that? We would like to know exactly what is troubling you, so that we can give you the most suitable suggestion for your use case.

From the top of my head, I would give you two recommendations for reducing file sizes, besides storing only the necessary channels:

• Reduce the sampling rate to the lowest usable value. Here, I would like to point out that you have the option of setting a custom sample rate for each channel

• Another way to reduce the datafile size would be to store the data files as .dxz instead of .dxs, meaning, that Dewesoft zipps the datafile. This option can be enabled in Settings, Storing, Data files.

Additionally, if you are running low on space on your measurement PC, you could use the DataManager plugin to copy the data to a different folder/different disk and delete the datafile from the default folder from Dewesoft.

Unfortunately what you are suggesting cannot be implemented because offline Math cannot be used on reduced data.

As mentioned previously, when we are storing data as slow, Dewesoft acquires data with full speed, then calculates the MIN, MAX, AVE, RMS for the time interval (set with static acquisition rate) and only stores these values.

As you can see on the image below, the slow stored data is shown as the envelope of the original, since the full rate is no longer available.

You can see the difference in the way the reduced values (left) and full speed values (right) are displayed. The behaviour of such data is shown below:

We can say that, when we are working with reduced data, we do not have any feasible Real data we can work with. If we change the Y axis display type form Real value to, for instance Average, we will get the calculated AVE values, with one ''sample'' every 0.5s (our reduced sample rate is 0.5s), but, this are calculated values that cannot be used in Offline maths. In other words, if data is saved with reduced rate, the samples needed to do offline math aren't available.

Best regards,

Pika

Hi @Pika Kreča Šmid

Thanks for the reply.

I currently customize the sample rate per channel to optimize the file size. I also enabled the zipped file .dxz option and that helped the file size but not enough. FYI for anyone following this.... enabling the .dxz option replaces the .dxd file... so you only get the one file (.dxz) at the end. I haven't encountered any downsides to saving as a dxz file.

I measure a lot of pressures, temperatures and flowrates and a 1 Hz sample rate is completely acceptable for these variables for the duration of the 2-8 hour test. I also measure vibration (via proximity probes) and fast sampling (20kHz, max of IOLite-LV) is required to periodically capture scopes and FFT spectrums. Therefore the "fast on trigger slow otherwise" storing method seems to be appropriate for my application. I do a fast trigger for 2 seconds every ten minutes or so. Currently my files are 100MB to 1 GB. If I used the fast storing method, my files would be tens to hundreds of GBs for every test which is not acceptable for several reasons (storage, transferring, post-processing).

So my feature request stays the same..... I'd like for the developers to adjust the slow storing method / options to permit offline math to work on slow data. For my application performing offline math on the reduced rate average values would be completely acceptable. This improvement would add a lot of value for me.

Thanks

Matt

Dear Matt,

To recap, you would like the option to choose which calculations are done to achieve slow stored data. This means that the user would be able to choose between MIN, MAX,RMS, AVE, having the ability to choose either multiple types or just one calculation type. You request that, should they choose just one type from the list, the user should be able to apply offline mathematics to the slow stored data.

Could you please tell me exactly which Mathematics from the list you would apply to this slow stored data if this option were available?

Best regards,

Pika

@Pika Kreča Šmid

Thanks. You captured my request correctly.

Currently, I'd be interested in using the following offline math features with slow stored data:

• Formulas
• Latch value math
• C++ script

If possible, these would be nice as well:

• Control channel writer
• Basic statistics
• Scaling

Thanks!

Matt

Dear Matt,

as requested, I reported the contents of this thread to the developers as a feature request.

Should there be any news (implementation of such a feature request would require rather extensive changes to our software), I will notify you.

Best regards,

Pika