analog outputs

[mady]

Hai NI

              I am using NI devices like 1 )chasis 1000 2) DMM PCI-4060  3)  SCXI -1331 4) SCXI-1127 . I am using an ordinary voltage generator, usually I use 12 volts ,I am working in 2 wire mode.I want to switch this voltage from channel 0 - 31 with certain time spam say about 1 minute at the same time I want to measure the voltage of the remainining 31 channels. I tried this by connecting my voltage generator terminals to out 0+ and out - but that voltage is going to all the 31 channels. I suppose that I have a problem with my VI ,I am sending my VI please take a look at it and suggest me. Am I doing the right method or is there any other VI to do this experiment and where should i exactly connect my voltage generator terminals.

 I hope you respond soon and in the affirmative

Regards

Madhava

[NI-Bongo]

Hello Madhava,

I believe you are seeing this behavior because you are connecting the DMM directly to the voltage source by using the Out0+ and Out0-.  Take a look at the picture in NI Switches Help»Devices»NI SCXI-1127/1128»2-Wire 32×1 Multiplexer Topology.  You can see that the AB0+ and AB0- (the analog bus) are connected whenever you do a scan with the 4060, so the DMM is connected directly to the voltage source.

To do what you want, you need a matrix, not a multiplexer (a 32x2 topology).  The SCXI 1129 has a 2-Wire 8x32 matrix topology that I think would meet your requirements:

NI SCXI 1129
http://sine.ni.com/nips/cds/view/p/lang/en/nid/3394

Another possible workaround is to get an additional SCXI 1127, connect channels 0-31 together between the two modules, and use them as if they were a 32x2 matrix.  I hope this helps!

[mady]

Hai John

            I hope you are doing great, thanks for your suggestion I have got two SCXI-1127 and two SCXI-1331,now let me ask u these things so i will use connect 0-15 of the first SCXI 1127 and use this for the switching the analog output voltage and the other SCXI 1127 will connect 16 channels and get the voltages parallely .I embedded these 2 SCXI 1127 in modules 4 and 1 of my chasis(i.e., the SCXI in 4 th slot is used for switching and the other one for measuring).Now where shoul i provide my analog output i.e.e my input voltage from voltage generator thats my major question and I am bit confused with the resource names and trigger inputs , I am sending my VI please indicate me the exact resource names and inputs to be used , it would be a great help. I am not sure whether my VI is right or wrong please take a look at it and suggest me. once again thanks for your great help

Best

Madhava

[NI-Bongo]

Hi Madhava,

Just to be sure, if you have the switches configured in 2-Wire 32x1 mode, you will need to connect together all the channels that you wish to measure and provide voltage to, (as you said, connect each channel in parallel).

You can connect the DMM to the Out0+ and Out0- of one module and connect the voltage source to the Out0+ and Out0- of the other module.  You will also need to connect the DMM Measurement Complete (MC) signal (DMM AUX line 6) to both of the switch modules using the “EXTTRIGIN” pin on the 1331.  Then set the trigger input on your switch modules to be “External.” Every time the DMM finishes a measurement, it sends a pulse to advance the scanlist on this line.

Now, to do the scanning, let’s assume you’ve done the above connections and you have 2 scan lists, as in your program.  Configure one scan list for the module switching the voltage source and one scan list for the DMM.  They will both be triggered by the same MC signal from the DMM, so we will consider that in the scan list.  Let’s say we will first configure the switches to apply a voltage across ch0 and measure the voltage across ch1 through ch31.

Switch with voltage source on common scan list:

Ch0->com0;

Ch0->com0;
...

Ch0->com0;

(One connection for each voltage measurement on the other module)

Then switch the voltage to the next pin,

Ch1->com0;

Ch1->com0;

...

Ch1->com0;

And so on.

Simultaneously, the other module will run this scan list.

Switch with voltage source on common scan list:

Ch1:31->com0; (Shorthand to scan 1 to 31)

Ch0->com0;

Ch->2:31->com0; (note we skip the channel connected to the source as it will now be on ch1)
...
And so on.

This is one way to apply a voltage on each channel and measure the voltage on the others.  You could use other triggering schemes to do something similar.  For more information on the pinouts, triggering signals, and scan list conventions, see:

NI Switches Help
https://www.ni.com/docs/en-US/bundle/ni-switch/page/user-manual-welcome.html

NI Digital Multimeters Help

https://www.ni.com/docs/en-US/bundle/ni-dmm/page/ni-dmm.html

Let me know if you have other questions.

[mady]

HI John

              As you know I am using two SCXI-1127 two switch simultaneously, the problem I am facing is that onlu one multiplexer is switching and that to be the top one of my VI.

Even if I click the next connection of my second multiplexer the channel of my 1st multiplexer is switching I guess there is a problem in my VI .please take a look at it and if could possibly modify that and send me the modified  one . It would be a great help . I would really want to appreciate for your excellent support that u have been providing me in this experiment.

Regards

Madhava

[NI-Bongo]

Hi Madhava,

Is the second switch ever switching? If not, then the problem might be that in your current VI, both operations refer to the SC1Mod1.  Make sure the other scan list uses SC1Mod2.  Check that and let me know the behavior of your second switch.

[mady]

Hi John

             Yes I changed the modules  like 4 and 1 and the configuration mode as 2  wire mode, but the second switch is n't switching at all. only the first switch is switching.

regards

madhava

[PBear]

Hi Madhava,

I took a look at your VI and I agree that you need to change the resource name 2 field to your second SCXI module. From your other posts, I think your second module is located in slot 4 so resource name 2 would be SC1Mod4 but ultimately it needs to be the same as how MAX references it.

[mady]

Hi Patrick

           Yes I have changed my resource names according to the slots alloted and my MAk references but still I get the same problem, so please consider this issue again
Thanks
Madhava

[PBear]

Hi Madhava,

Other than changing the SCMod1 to SCMod2 and making sure that the topologies corresponding to the respective devices. This may be an issue with the SCXI controller but I'll wait to hear back from some of my internal contacts about that. Can you try changing the program so that the two switches don't run independently? This may be a temporary solution as we look into why this isn't working for you.