DAQmx and Cascading SCXI 1140 and 1143

[dimented]

I am trying to configure my SCXI chassis through NI MAX and DAQmx. I wish to cascade a SCXI 1140 and 1143 so I can use the track and hold circuitry to make synchronized measurements. I found a thread here about how to configure the modules with a SCXI 1352 cable but it says nothing about DAQmx. My ultimate goal is to sychronize these measurements with a SCXI 1520 strain gauge module

[Bill B]

Hello,

Thank you for contacting National Instruments.

At this time, the DAQmx driver does not officially support cascading configurations. However, follow these steps and you should be able to cascade your signals. (I am going to assume in these steps that you only have two modules in your chassis.)

1. Connect the SCXI-1352 cable to the 16-pin header inside the SCXI-1140.
2. Connect the other end of the SCXI-1352 to the rear of your SCXI-1143.
3. Connect your SCXI-1349 adapter with your DAQ cable to the rear of your SCXI-1140.
4. Configure both modules to operate in mulilplexed mode.

With this configuration, you will be able to connect 8 analog input signals into your SCXI-1143 module. This signals will be filtered and then passed through the SCXI
-1352 cable to your SCXI-1140 where they will be simultaneously sampled and then sent to your DAQ board for maeasurment. You will not need a terminal block on the front of your SCXI-1140 if you are passing all 8 signals through your SCXI-1143.

Please look at this tutorial for additional information: http://zone.ni.com/devzone/conceptd.nsf/webmain/9330CB13E1D6169386256B79005A842B?opendocument

Regards,
Bill B
Applications Engineer
National Instruments

[Ole_H]

I have used this setup and configured the 1143 to operate in parallell. Is that incorrect then?
Ole Hatteböl

[dimented]

were you using DAQmx?

[Bill B]

Ole,

If you are using DAQmx, the driver will require that you have a dedicated board connected to your SCXI-1143. You will want to leave the module in multiplexed mode so that you can control it using a single board. Even though the module is in multiplexed mode, you can still cascade the signals to the SCXI-1140. You will then read your signals from your SCXI-1140. Realize that your signals may not be scaled correctly when measured from the SCXI-1140 if you had applied a gain at the SCXI-1143.

Regards,
Bill B

[Swimmer]

Bill,

I have a similar situation, I'm using the 1140 and an 1143.  I have them cascaded together using the appropriate cable.

I'm using an SCXI-1600 for my A to D

Assume I have 2 channels on the 1143, I'm filtering them and then want to read SS&H through the 1140.

To get this to work I've had to set up a task that contains 4 channels.  Ch 0 & 1 on both the 1143 & 1140.  This allows me to set up the filter on the 1143, which seems to only be setable through the task.

The problem is that I have to read 4 channels instead of 2 thus cutting my bandwidth in half.  Not desireable.

Any suggestions on how to set up the 1143 channels so that they pass through to the 1140 with the correct filtering but not being read?

Thanks,

Dave

[Travis G.]

Hello Bill,

Unfortunately, the cascading combination of an SCXI 1143 and SCXI 1140 module is only supported in Traditional NI-DAQ.  Since you are using the SCXI 1600, which is only supported in NI-DAQmx, this will be a problem.  You can see what cascading configurations are supported under different versions of the driver by looking at this document:

Developer Zone Tutorial: Cascading SCXI Modules

In Traditional NI-DAQ, you set the filter settings for all eight channels of the SCXI 1143 under Devices & Interfaces, rather than through a task in Data Neighborhood.  This allows you to set the filter settings without creating a task.  You could try to replace the SCXI-1600 with a DAQ card that supports Traditional NI-DAQ, and use the instructions in the following Knowledgebase to configure the system in MAX:

KB 26CDD2WZ: Configuring the SCXI-1140 and SCXI-1141/1142/1143 in Cascaded Mode

I hope this information helps.

Regards,
Travis G.
Applications Engineering

[Swimmer]

Travis,

Thanks.  I finally came to the same conclusion with the help of a few guys from tech support.  You may have been one of them.

The current solution has been to switch to an SCXI card that is jumper configurable.  I chose the 1120D.  This module is not present in the SCXI chassis configuration. 

So now I have some lowpass filtering, Gain of 0.5 so that I can read a 10V signal, and isolation.  I used the 1352 cable kit to cascade the 1120D to the 1140 to get simultaneous sampling also. 

This set up works well with the SCXI 1600.  The only issue is the sample rate.  But for only 8 channels it's not too bad.

One item worth mentioning when using the SCXI-1600:  In the SCXI Chassis configuration>, in the details for any given module>, under the cabling tab>, in the "Which Device Connects to this Module" pull down:  Do not select the 1600 here.  This refers to a device that is connected to the rear connector through a 1349.  If this option is chosen the 1600 won't be able to read the 1140.

Thanks

Dave