trying to measure voltage through 1 wire connection

[mady]

Hai ,

       I am trying to measure voltage through 1 wire connection using NI hardwares like  1)chasis SCXI-1000   2) DMM PCI- 4060, 3) MUX SCXI-1127 and 4) Terminal Block SCXI-1331. Please see a attached picture of my set up.

  I am unable to establish my connection through  1_WIRE_LO_REF .I want to use it  as my reference point (GND) through which I can measure the voltage .I think there may be problem in my design or in the labview code.Could u please verify   and suggest the appropriate one.

Can I use 1_wire_Lo_ref is so which port to be used, actually i have six ports for this point (or) is there any altenative

 I hope u respond soon and in the affirmative

with regards

madhava

[AnalogKid2DigitalMan]

madhava:

I do not have any suggestions for your 1 wire connection, but I do have so advice regarding the wiring:

Cut back the lengths on the exposed copper portions of your wires- some are already close to shorting to one another. You should not be able to see hardly any exposed copper. A little work now can prevent a disaster later, especially if the wires get moved around. If you do decide to cut them back, make your cuts away from the equipment so the little pieces of wire do not get in your card and create additional problems.

-AK2DM

[tbob]

I haven't studied your vi at length, but you can see by the black shadow to the right and below the NIDMM subvi's inside the loop that these subvi's are not really inside the loop at all.  They are just placed on top of the loop and not wired inside the loop.  This is probably your source of problems.  Drag the subvi's outside the loop, disconnect the wires, move them back inside the loop, and then reconnect the wires.  You should not see the shadows.  If you meant to put the subvi's outside the loop, move them to below or above the loop structure.

[Nick_F1]

Hi Madhava,

Thank you for posting on the National Instruments forums.

You can definitely do what you are trying to do.  In the one wire topology, 1_WIRE_LO_REF stays connected and the other signal multiplexes through your channels.  One thing I noticed with your VI is that you do not have the trigger source wired in the DMM trigger setup vi.  This could possible make it so that when the switch sends a trigger that it is done the DMM won't see it. 

I would suggest opening the NI Example Finder, go to Hardware Input and Output >> Modular Instruments >> NI-SWITCH (Switches) >> niSwitch DMM Switch Handshaking.vi.  You can compare what is different between the two and change yours to match this example.  Please let me know if you have trouble getting this to work.

[mady]

Thanks Nick for your fine reply  to my thread. You said that I need to modify my Vi  according to the niSwitch DMM Switch Handshaking.vi. I tried that but I am unable to get the results I face the same problem and i dont understand about the trigger source for  DMM.Vi . I also face  a problem  with  the  channel scan  list  I am unable to give correct form for that scan.
So, I want you to moderate my VI   according to the DMM Switch hand shaking .vi and as per my requirements.I  request you to please show concern and i want  you to post me the moderated Vi  file.My Vi  and my circuit set up is in my first post  please refer to that.
              I hope you understand my problem and respond in the affirmative

Thanking You
Madhava

[Nick_F1]

Hi Madhava,

Are you unable to get the example program to work?  Are you using an Aux cable to connect the switch to the DMM or are you triggering from the connector block of the switch?

One good resource is to open the NI-Switches Help from Start >> Programs >> National Instruments >> NI-Switch >> Documentation >> NI-Switches Help.  Go to the Search tab and search for Single Module Scanning - Handshaking.  There are sections for SCXI or PXI depending on which form factor you are using.  This will explain which triggers to use and how to connect the DMM and Switch together.

In the same help file, if you search for Scan Lists, this will show you the proper syntax for the scan lists.  The scan list can all be listed in one text box and does not have to be an array of strings. 

I think the best way to proceed is to take the example that I showed you save it as a new program so you can go back to the original if you need, make it work and then modify it to do what you need.  Add the write to file for example.  If you have any questions about specific issues, I can help you with those.