Multiplexer with NI elvis kit

[HEAPO8]

Hi I have developed a code which looks at 2 analogue inputs in the NI Elvis Kit II. My hardware has 2 Arduino 4051 multiplexers connected to a NI Elvis Kit II. Each multiplexer is able to connect to 1 analogue I/O on the elvis kit and because the multiplexer has 8 pins, it is able to produce 8 analogue I/O (So the arduino 4051 makes one NI Elvis analogue, have up to 8 analogue I/O).

I want to be able to read 16 analogue inputs on my intensity graph. I am hence using 2 analogue inputs on the NI Elvis Kit (8 analogue I/O for each input on the Elvis Kit). I am able to view data for Analogue Input 1, but I can see nothing for Analogue Input 2. I have the code connected to this post- can anyone help? It's [probably really simple but I am stumped by it at the moment! Cheers!

[Clad19]

Hi HEAPO8,

Thanks for your post.

I understand what you are trying to do.

When you mention you cannot see any values on AI2, what do you mean? I ran your code here and I am able to run simulated values on all 16 AI. 

I can see the application cycle through all channels.

Have you checked the wiring of your second arduino multiplexer? 

The only thing that would affect the AI is the DAQ Assistant in regards to code. Everything else seems fine.

If you could let me know how you get on, that would be great.

Kind Regards,

[HEAPO8]

Hi, thanks for your response. I am actually getting readings now so that part of my problem has been fixed. the problem i now have is that readings from one multiplexer are being superimposed onto another. I am using 2 arduino 4051 multiplexers and the readings are being superimposed on each other. I have heard about this type of problem before but i cannot remember the name for it. Do you know what it is and how I can prevent it? Cheers

[Clad19]

Hi HEAPO8.

I'm glad you managed to get that all working nicely! 

I believe the issue you are seeing could be either crosstalk or ghosting between the AI channels. This is a common phenomenon. Here are some articles relating to it and how to reduce the effect:

- What is the Difference Between Crosstalk and Ghosting?

- Troubleshooting Unexpected Voltages, Floating, or Crosstalk on Analog Input Channels

- Decreasing the Source Impedance of an Analog Input Signal

- How Do I Eliminate Ghosting From My Measurements?

- Why am I getting bad readings when using a DAQ Assistant with multiple channels?

I hope this helps!

Best of luck with your application.

Kind Regards,