correct scan list for PXI-2503 multiplexer

[m@NI_forum]

I'm using PXI-4071 DMM and PXI-2503 multiplexer to scan 10 resistors (1000-4000 Ohm) in 4-wire mode. DMM and the multiplexer are connected by standard cable (4 bananas to Analog Bus Connector on TB-2605). In Test Panels of MAX I can measure all resistors correctly by connecting com0 to ab0 and by switching channels 0 - 9 to com0, but I cannot write a correct scan list for a VI that would allow me to get correct measurements. I tryed com0->ab0 && ch0:9->com0 which should work accourding to my understanding of the manual, but it doesn't work. Can anyone advise me the correct scan list?

By the way I also have wires connected to com0 terminals in TB-2605 block and when I connect these wires to DMM instead of a standard connector VI works with the following scan list ch0:9->com0.

[nelghazawy]

Hi,

Thanks for your post, to help debug the issue, could you please let me know:

1. When you mentioned that you can read the resistance in NIMAX is that individual resistances? In case yes, can you do the same thing from LabVIEW? Reading only one resistance using the same Vi you provided?
2. Could you also explain what are the results you are getting from using this code? Does it just not work or it gives an error? In case it give an error, what error message are you getting?
3. What is the rate at which you are multiplexing? Does it make any difference if you changed this rate or tried to read less channels?

Thanks,

Nour Elghazawy

[m@NI_forum]

Thanks for replying to my post.

1. I can measure resistances in NI MAX because I can manually connect com0 with ab0 (see picture attached). I cannot measure resistances via my VI because I don't know how to instruct multiplexer via LabVIEW to keep com0 & ab0 connected while I'm scanning channels. And that is exactly the objective. When com0 is disconnected from ab0 I have an open circuit all the time.

2. VI is not giving errors, it just measures rubbish.

3. Multiplexing rates I tried were in a range 1 to 50 Hz. It doesn't affect the result. I don't remember what was the result when I tried to read just one channel with the scan list com0->ab0 && ch0->com0, but even if it works, it doesn't give me a clue how to compose a scan list for scanning 10 channels. I'll try that again though whan hardware will be available and update my post.