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

Hi Sven,

I bought the new harness but there is not label on them that shows new definitions. I could not find the labels in vector's manual also. I have Gnd, analog ch. 1, analog ch. 2, Power out in my cable. The harness 10 wires from one side and 9 wires (7 and 2) in another side. I am not sure which one I should choose to get sync in and sync out that I need. Thanks.

-Abbas

Hi Abbas,

 

The synch in signal is to be found where it is labelled pwr out

while synch out is to be found where it is labelled Analog ch. 2

GND is to be found at to terminal labelled GND  

 

Best regards

Jonas Røstad

 

Thanks Jonas and Sven,

Vector is now synced with vectrino and they are happily living together. I have one more question. So, I set the vectrino to measure for 4 minutes. The vectrino and vector start at the same time. But, when the 4 minutes passes, vector keeps getting data in spite of vectrino has already stopped. Is there a wise solution to stop the vector at the exact moment that vectrino stops? I might be able to give vector a time limit (4 minutes for example) but that would not be that accurate I think. What do you think?

Abbas

Dear Abbas,

Have you check both boxes for start on sync and sample on sync ?

-Jonas-

Hi Jonas,

Thanks for your reply. Yes. I check both boxes. It is not a big deal though. Since they start recording at the same time, I will not use the extra data from VECTOR. 

-Abbas

Hi Abbas,

 

Are you sure the Vector is giving out velocity data and not only sensor data?

Below you'll find how the system data are output in this arrangement.

 

Output of the Vector system data (compass, tilt and temperature) is not synchronized

between different Vectors through the use of the SyncIn signal. Instead,

the start on the sync edge that is present in both synchronization modes is used

to start the 1 Hz output of the system data. Each Vector will then output its system

data based on its internal real time clock. This implies that the number of

system data outputs may vary slightly from one instrument to another. Note that

this is not a problem for the synchronization of the velocity measurements. The

compass and tilt data are used internally in the Vector to ensure correct transformation

of the velocities to earth coordinates when ENU is selected as coordinate

system.

Best regards

Jonas Røstad

 

 

Previously Sven Nylund wrote:

Hi Sven, 

I'm currently trying to sync multiple Vectrinos through an external TLL source. Currently, I have two separate Vectrino cords with Sync + and Sync -, and one with Sync In and Sync Out. The Sync (+) is connected to the Sync Out port of the second Vectrino and the input pulse, and the Sync (-) port and Sync In ports connected to each other and a constant voltage source of 1.5V as recommended. With this configuration, the Vectrinos start spontaneously when in Start on Sync mode rather than with the transmitted pulse. What would be a correct configuration for this set-up?

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.

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.

 

Dear Lauren,