mxi-4 reduce bus rate

[scoobydont]

Hi

I am using a PXI 1044 chassis and standard windows pc with a MXI-4 link and was wondering if it posible to reduce the bus rate between the two.

many thanks

Darren

[Andrew McL]

Hi Darren,

I was wondering if you could provide a little more information on why you want to reduce the bus rate between the PXI and PCI. Also, what sort of MXI link are you using? 

Many thanks,

[scoobydont]

Hi Andrew

I'm using a PXI 8331 MXI-4 with 10metre copper cable in slot one of a PXI-1044 chassis and a pc with PCI card.

The desire to slow the bus rate comes from a need to perform a one off test with the link cable passing through a very noisy area. I'm recorded and sending very low rates of data from the chassis. An inital trial has shown that the 10m cable with its high transfer rate may be beyond the limit of its performance. I was hoping to reduce the bus rate in an attempt to increase signal quality.

many thanks

Darren

[Andrew McL]

Hi Darren,

I'm afraid I don't think you'll be able to adjust the timing on the bus as this would affect the way the cards send and receive information. I noticed that you said you are using a 10m cable. This is the maximum cable length that we recommend for a copper MXI-4 connection so I think you only really have a couple of options.

1. If you want to communicate with the PXI chassis away from the PC, you could have a look at the MXI-4 fibre optic connection. This allows you to run a PXI chassis up to 200m meters between connections. 

2. Would you be able to reduce the length of cable between the PXI chassis and the PC? A smaller cable should give better results.

3. Is there any possibility that you could reduce the cables exposure to noise? Either by insulating it or removing some of the noise producing elements?

Please let me know your thoughts.

Thanks,

[scoobydont]

Hi Andrew

thanks for your reply.

There's no way we can shorten the cable, if anything I would like to make it longer. The noise issue can't really be avoided as there is no option other then to pass two very large pieces of rotating machinery. Fiber optics would work but as this is a one off the cost is prohibitive. Would it be possible to boost the signal somehow?

thanks

Darren

[Andrew McL · Accepted solution]

Hi Darren,

I have  been looking at your problem and I am not sure what else we can do. 10m is the maximum cable length for a copper MXI-4 connection and I think if you used a longer cable, the link probably wouldn't work at all.  I've attached a link here to the datasheet for the MXI-4 specifications. If you look at Appendix B, this gives a more detailed explanation of the limitations of the MXI-4 cabling. 

As far as boosting the signal, a standard Ethernet booster will not work as it will interfere with the composition of the packets being sent. 

I accept these are not very pleasing results and I am sorry that I cannot help. I've summarised the options that I feel are available to try and improve this problem

1. Change the MXI-4 Copper link for a MXI-4 fibre optic link

2. Buy another MXI-4 Copper link, a second PXI chassis and use the second chassis as a relay point for packets to the PC.

3. Attempt to remove some of the noise, either by encasing the cable in something or rerouting it. 

I would certainly look at trying to reroute the MXI-4 cable and also look at trying some additional shielding to reduce some of the EMI issues but I think the best option would have to be the Fibre optic kit.

If you are looking at option 2, I would strongly recommend looking at the  NI PXI-1033 linked here, as this is an expansion chassis and MXI link that can be used to extend your setup. If you are at all in doubt, I would contact National Instruments and speak to an Inside Sales engineer who will better able to advise you on your issue.

I hope this helps.

Many thanks,

[scoobydont]

Hi Andrew

thanks for your help. I agree fibre optic would be the way to go for a perminant installation. All other sensors in the 'noisy' area fibre optic. As this will be a one off I'm going to use a borrowed PXI chassis as a relay.

many thanks

Darren