Split signals voltages

[Rysc]

Hello NI community

My partner and I have a question about routing a timing signal from one PFI 7 pin on one DAQ card to other PFI pins in other DAQ cards. (DAQ cards in use are 6071E)

To do this we thought about using a splitter to split this signal in between stations, however this may decrease the magnitude of the signal, which may in turn affect the transmitted Master clock signal that we are designing for. Because of this inquiry we may have to consider a dasiy chain connection however latency may be an issue using this kind of connecton.

The question is this then, if we split a timing signal can we expect the same performance for the signal to be split to the other DAQ cards, what we consider when we split a a timing signal, i.e.voltages, power, currents etc.

If you need any more clarity please contact me back.

Thanks

Ryan

[tnek]

Hi Ryan,

 Depending on your situation there may be other options. Are these boards PCI or  PXI? If they are PCI and within the same chassis, you can use a RTSI cable to pass the signal. If you are using PXI cards within the same chassis, there are trigger lines built into the backplane of the PXI chassis. If the signal needs to be passed to multiple PXI chassis, there are timing and synchronization boards which can accomplish this. All of that being said, daisy chaining the signal will insert a propogation delay but this will be very small compared to the sample rate of the card and can be compenstated for. Splitting a signal will be fine as long as the resultant signals meet TTL specifications. A better way of transmitting the signal may be to put the same outgoing signal on multiple PFI lines.Hopefully this gives you a few more ideas about how to transmit your signal.

Regards,

Kent

National Instruments

Applications Engineering

[Rysc]

Kent

Thank you for the response, unfortunately while using the PXI back chassis or a multiple synchronization board sounds very reliable and resourceful, we are limited to only 4 PCI - 6071E DAQ cards located at each of their respective chassis. 

That is why we are deciding to consider using PFI pins over the RTSI on the card for synchronization, we plan on having any one station as the master connection where it uses its PFI pin as a triggering signal for the slave connected DAQ cards.

I was wondering about the point you had mentioned:

"A better way of transmitting the signal may be to put the same outgoing signal on multiple PFI lines"

Would it be possible to send these signals synchronously? In other words do we have to be concerned about latencies with respect to signals from different pins?

 Three of the design schemes we have planned so far include:

1) Using a daisy chain connection

2) Using multiple PFIs as you had mentioned to interconnect the DAQs

3) To use a single PFI which is split between the three DAQs, thereby  any DAQ can be the master by allowing that pin to be an output and the other slaves to act as inputs. 

 Have any of the above mentioned schemes ever been done using E series devices or anything similar, what drawbacks do you think exist from these connections? Also do they have naming conventions already?

I apologize if I seem abrasive, but we do appreciate the help.

Thanks

Ryan

Message Edited by Rysc on 01-20-2009 04:40 PM

[tnek]

Hi Ryan,

Any of these methods will work with your E-series devices. You just have to be aware of the possible delays or attenuations. They are all fairly simple to implement so the best way to find out what works for you may just be to try. 

Regards,

Kent

National Instruments

Applications Engineering