Some basic SCXI questions

[Vr6Fidelity]

I have a SCXI system here with 3 modules.

It was installed and set up by someone who no longer works here. I am pretty comfortable with cards, and scb-68's and what not.

I do have a couple of questions about this SCXI though.

1. When in MAX, if I start a NEW configuration, the SCXI is NOT there. But if I copy an existing config (save as) It is there. Out of curiosity, how do I "summon" the SCXI from a new config from scratch?

2. MODULES:

I have a PCI-MIO-16XE-50 as device 1.
I have a SCXI 1000 as Chassis 1.

In the SCXI I have 3/4 connectors, MD1-MD3.

MD1 and MD3 have a 1303 terminal block.

MD2 has a 1302 terminal block.

In my traditional (LV 6.1) max configuration:

MD1 is for all thermocouples.
MD3 is for high speed dynamic signals

here is where it gets interesting:

MD2 is just pinned out directly to the 16XE-50? Why?

My real question is why is MD2 setup to pin directly to the board, and from max assigned to 16XE-50 channels directly, while the other two modules are setup as "SCXI1102-DEV1_SC1_MD1"?

What is the purpose of this? is there any advantages or drawbacks to using the SCXI platform VS. pining directly to the cardthru the SCXI module?

Thanks.

[Vr6Fidelity]

anybody? Is this thing on?

[Vr6Fidelity]

Hellooooooo?

[Ana P]

Hi,

You can create a new configuration of the chassis in Measurement and Automation Explorer. I understand that you are using the Traditional DAQ drivers, if so in MAX right click on Traditional NI-DAQ (Legacy) Devices, select Add SCXI chassis, choose the SCXI chassis type and follow the directions. In your current configuration you can verify which module is connected to the DAQ card by right clicking in the modules and select Properties. I understand that when you say that MD2 is pin out to the card you mean it is connected to the DAQ card. When you configure a new chassis you will notice that you can manually insert the modules in the chassis or select Auto detect, also you will have to select which module is connected to the DAQ card. I understand that you have only one DAQ card, so you must have one SCXI module connected to that DAQ card in your PC, and that module will show the PCI-MIO-16XE-50 in the “Connected to” field. The “Connected to” field should be “None” for all the other modules. I hope this is helpful, please let me know if I misunderstood your questions.

[Vr6Fidelity]

Admittedly, I know very little of the SCXI system.

I have the 16-xe-50 card "connected to" md1.

I have 3 modules, and they are all listed, yet in my virtual channels things wired to MD2 are set to channels on the 16xe50, not to MD2 as it has been done with all connections to MD1 or MD3.

Why would it be done like that?

Is there a speed or accuracy advantage to assigning the channels to MD2 over the 16-xe-50? All the wires go to the same place, the only difference is the settings.

This is really what I would like explained.

ALSO:

The three SCXI modules, are they like cards? Do they have individual sampling rate capabilities and accuracies? I have MD1 for thermocouples, but does that mean its a module designed for TC's? I know it has a special iso-thermal terminal block, and it has a positive and negative spot for each channel (ach1+,ach1-)

My MD3 seems to be for high speed signals, and MD2 isnt really being used as a module at all, more like a terminal block for the 16-xe-50.

Could you shed a bit of light on how this setup is working? It does work.

[Ana P]

Hi,

The SCXI is an extension for the conditioning of your signals. You need conditioning for some signals that are really low level and their measurement could be erroneous when connected directly to the PC. For example, the thermocouple measurements are low voltage values; therefore some signal conditioning is preferred before feeding these signals to the DAQ card. Your DAQ card (PCI-MIO-16XE-50) has a specific sample rate; and the sample rate of your system will depend on several factors. This knowledge base explains the relationship. More information about the modules you are using can be found in the modules' user manual.

 

You could directly connect the conditioned signals to the DAQ card, but using the SCXI system you can measure more signals than what you could measure by connecting directly to the card. The outputs of your SCXI modules are connected to a multiplexer that passes those signals to the DAQ device. This article might be helpful in understanding how the signals are connected in the system. You don’t say what the modules in your chassis are; so I’m assuming that for the thermocouple measurements you are using the SCXI-1102 with the 1303 accessory. Please confirm that information. Another really good place to look at is the Getting Started with SCXI manual.

 

Regarding to your module 2 that is directly pin out to the card, I’m assuming that you are using the SCXI-1180 module. That module is usually used to extend signal lines (from your DAQ card) that don’t require signal conditioning.  I can’t tell you why they are using those lines directly; it is really dependent in your specific application. My best assumption is that in those terminals you are measuring signals that don’t need to be conditioned before. I hope this is helpful, if no please give us more information about the specific modules that you are using.