Synchronising multiple Vectrinos

I am afraid our Vectrino manual is not up to date regarding synchronisation Here is an explanation on how synchronisation is done with the Vectrino.

To cope with longer without having noise problems and to make the cabling easier the Vectrino uses RS485 as the electrical interface for synch. The two sync lines are labelled Sync+ and Sync-. To synchronise multiple Vectrinos simply connect all the Sync+ lines together and all the Sync- lines together. In the software you then select one instrument as the master and the rest as slaves (Input sync). All instruments should be configured with the same sampling rate if you use sample on sync.

Some instruments have incorrect labels on the sync lines, if the labels read Sync in and Sync out they should be treated as Sync- (Sync In) and Sync+ (Sync Out). The polarity is not too important as the sync scheme is quite insensitive to the polarity.

Now for the details on how the actual synchronization is done. There are no plans to change this, but for reference the following applies to all firmware versions of the Vectrino up to and including v1.27:
- Output Sync (operation as Master) outputs a pulse on RS485 with duration 40us. Sync out for Vectrino outputs the pulse at the end of the sampling interval, Sync out for other sensor outputs a pulse at the middle of the sampling interval.
- Input Sync triggers on any edge (both rising and falling) on RS485. After each trig the input is discarded for the next 64us.

It is possible to mix TTL signal levels with the RS485 levels of the Vectrino, but some precautions are necessary. For Input Sync, the following RS485 levels define the signal that is read by the Vectrino:
Sync+ > Sync- by 200mV is interpreted as high level
Sync+ < Sync- by 200mv is interpreted as low level

This means that if you want to sync the Vectrino from a TTL source you should connect your sync pulse to Sync+ and connect Sync- to a constant voltage, for example 1.5 volts. You will then have a defined transition when the TTL signal changes (this is not the case if you ground Sync-).

When running the Vectrino as a master the Sync+ line can be connected to the TTL input (common ground for the two systems). If there are noise problems it will help to terminate the Sync+ line at the TTL input by connecting a 120ohm resistor in series with a 1nF capacitor between the Sync+ line and ground. If possible, the best solution for external sync would of course be to use RS485 as the input/output device.

Best regards,

Sven Nylund

Hi Sven,

I know it has been a few years since your post. I want to sync a vectrino and a vector. From your post, it seems that the vectrino should be the master and vector the slave. I have some questions:

1) Is the vectrino plus software enough or we should have the vector's software separate?

2) on my vectrino, I see sync1, sync2, A1, A2, A3, A4 and GND. I do not see sync - and sync +. Should I sue sync1 and sync2 instead of sync- and sync+?

3) Do I need a controller? 

If you provide the steps I should do with more details, I will appreciate it.

Abbas

Hi Abbas,

1) Is the vectrino plus software enough or we should have the vector's software separate?

You need to run one instance of the software per instrument so you need both the Vectrino Plus software and the Vector software.

2) on my vectrino, I see sync1, sync2, A1, A2, A3, A4 and GND. I do not see sync - and sync +. Should I sue sync1 and sync2 instead of sync- and sync+?

It should work even if you take either one, but you can consider sync2 to be the same as sync+ so sync1 is then the same as sync-.

3) Do I need a controller? 

No, just collect the data with the Vectrino Plus software and the Vector software.

To repeat what is described and to give a more complete description I have made an example of what you need to do here. This assumes a desired sampling rate of 30 Hz.

1. Connect ground of the two systems together
2. Connect sync+ (sync2) on the Vectrino to SyncInput on the Vector
3. Configure the Vectrino with the desired velocity range, 30 Hz sampling rate and select output sync for Vectrino and check the box for master
4. Configure the Vector with the desired velocity range, continuous sampling, the next higher available sample rate (so 32 Hz in this example) and check the boxes for start on sync and sample on sync
5. Select the file name for disk recording in both software instances and make sure you also start disk recording in both software instances at this point.
6. Press Start Data Collection in the Vector software
7. Press Start Data Collection in the Vectrino software
8. The measured data will now be shown on the display and stored to file, synchronized to each other.

The configuration for both instruments is shown in the attachment so you can start out with exactly this example to see how this works.

Best regards,

Sven Nylund

Hi Sven,

 

Thanks a lot. I really appreciate it. One more thing. The cable that I have for the vector has these 4 outputs : GND, power out, analog ch 1, analog ch 2. Apparently it is not the right one for syncing. Is there any way that I use this cable or I need to buy "RS232 cable with Synch in/out" ?

Thanks a lot,

Abbas

Hi Abbas,

You can re-use the cable but you need to purchase a new harness with a new label that shows how the signals have been redefined. The new definition can also be found in the Vector manual. 

Best regards,

Sven Nylund