Use 2x Sirius loggers without synchronization

Hello,

I need to do some slow measurements so synchronization between devices is not important.

Would be possible to have 2-3 units connected to one PC and use them without synchronization?

I tried yesterday but I got error about data acquisition. Is there a workaround for this or some special setting?

Thank you!

Best regards,

Andrei Ghiran

Multiple Sirius slices can only work on one computer if they are synchronized (IRIG or Clock/Trigger).

If you have the sync cable, this shouldn't be a problem.

Hi Dewesoft, I came across this post when looking into operating two Sirius slices physically separate from each other. Having simply a separate USB connection to the PC with no sync cable in between would be ideal. The measurements from the two units don't need to be hard synchronised (<1s is suffiicient), but on each slice will be performing inverter power measurement (>200kS/s). According to this application note, this should therefore be possible? https://dewesoft.com/blog/data-acquisition-synchronisation#multi-system-synchronization

Has this then been updated in Dewesoft to enable this? I have tested it on the desk and it seems to work, but is there any other concerns to take into account with longer duration measurements (e.g. will measurements drift?). We have previously tried with longer sync cables, but in the noisy environments this often gave sync errors. If this is reliable, this could be a more robust solution where hard sync is not needed.

Dear Edward,

thank you for reaching out to us.

The connection you speak of is called SoftSync connection. In general, this is what the interface looks like, if we connect two devices in such a way:

It looks like you are using two SIRIUS USB devices and in general, these should not support SoftSync synchronization, as you can read on this link as well.

Could you please let us know which devices you have connected, and what the Device settings look like?

Best regards,

Pika

Hi Pika,

they are 2x Sirius-HS USB units. The units are now out for some tests so cannot get a screenshot. But what I can recall from the test is that while the measurement was able to start, an 'Alarm' saying sync lost was then present. Not sure if that is then implying SoftSync was not there?

ed

Dear @Edward Sciberras,

as mentioned previously, the Sirius-HS USB devices are not compatible with SoftSync, meaning, that you need to use a sync cable between them in order for the sync to work, and to be able to collect the data. That is, because soft sync is usually used only if there is a low-speed device in the setup, such as a CAN device or Krypton TH, ...

The Warning that there was Sync Lost means just that- the two devices were not synced together, and you therefore are not able to continue data acquisition.

If you are still getting the Sync lost message after using the sync cable, please contact us, so that we can further assist you. What we will need is the log files of the warning, the devices you are trying to connect, and the Sync types (I have already shared the general image of this with you).

Hi @Pika Kreča Šmid

thanks for your reply. But now slightly confused since on my desk this worked and data acquisition was working without a sync cable. And also according to https://dewesoft.com/blog/data-acquisition-synchronisation#multi-system-synchronization then operating without a sync cable is possible?

If this is possible to work (not synchronised) then this is sufficient for my needs as long as the measurements do not drift more than 1s and Dewesoft does not crash?

ed

Dear Edward,

we tested this yesterday, using, among other devices (such as a SIRIUSi and Krypton) two Sirius HS devices. In the case of Krypton, we managed to get SoftSync synchronization going, as is expected.

When we tried to connect two HS devices, we couldn't get SoftSync to work. As a matter of fact, you shouldn't even be getting the option for SoftSync. I am attaching the image of the device setup (of a Krypton), where you can clearly see that the sync is set as SoftSync:

We did not get the SoftSync option for the Sirius HS devices (although I sadly do not have an image I could share with you here), which is also in line with both the solution SoftSync with CNT and EtherCAT devices, as well as the fact that the Sirius HS units run at high samples, so it's not convenient (not accurate enough) to use SoftSync. You can read more about the different types of synchronization here, but, as you can see, SoftSync and NTP both have accuracy <10ms, which is a much greater value than the other types of synchronization.

As per our experience, the NTP option doesn't work for Sirius devices either.

I am very curious as to whether or not the Synchronization was set to SoftSync or something else in your case, since, as stated before, SoftSync should not be possible with two Sirius HS devices.

Best regards,

Pika

Hi Pika,

Sirius slices were back and we were able to test this again. Here are the settings:

With the two Sirius HS slices connected without a sync cable, we were able to perform data acquisition at 200kHz. Below is screenshot of same sine wave measured on both units

As expected there are not synchronised, but that is OK for our purposes.

My question is, is this operation supported by Dewesoft (understanding the limits of unsynchronised data from the two slices)?

Hello Edward,

thank you for the update.

I can see that you are now using the IRIG-B DC synchronization. This is a standard format for transferring timing information and has a 1Hz Frame rate and a 5V amplitude.

This synchronization type depends on external hardware to ensure that the client can successfully complete data acquisition without errors and with without channel drift.

The principle of synchronization is this: Every time we leave the Settings tab, DewesoftX sets exact time to each device- the devices adjust themselves by the sync signal.

If we set synchronization to IRIG-B DC and do not use a sync cable between the devices, what we will usually get is an error: Start pulse not detected, which means that the data acquisition cannot begin, since the devices are not synced- the times are not the same. Using sync cables between the device ensures that they are operating at the same time.

In your case, it just so happened that once you've exited the Settings tab, DewesoftX assigned the same time to both devices, which enabled you to run data acquisition. It also looks like you have run a relatively short measurement. The duration of data acquisition is important, since the time of one device might start to drift more compared to the other device. If this happens, you can get two error messages- sync in overload and data lost.

Sync in overload means that DEWESoft needed to adjust time more than it is allowed, and it means that there is a bad signal for the synchronization. Data lost, on the other hand, means just that- the data was lost, and it is therefore not included in the datafile. 

In other words, if you don't have sync between the devices, you cannot guarantee that your data will be good- it can be lost, or it could have drifted too much to still be useful.

You reported there being sync errors with longer sync cables. Could you please tell us more about this? How far apart are the devices from each other, and from the computer the they are connected to? Could you tell us more about the environment the measurements are being taken in? What is causing the excessive noise?

Best regards,

Pika