cannot graph two separate voltages

[stitch182]

Hello

Newbie here.

I am having trouble trying to graph two separate voltages. When I check in MAX, on the test panels I can see the different voltages on separate channels, but when I load my labview program, the program only sees one channel on both graphs, even when the DAQ assistant is showing it is supposed to be reading  different channels.  I am using a 1052 chassis with a 6052 analog card and 1125 module with a 1327 accessory.  It used to work and it just starting doing this out of the blue, is there a blown fuse or a driver problem?

Can anyone help me?? or any ideas.

[Christian Mergl]

Hey,

If it works in MAX and not in LabVIEW its no hardware problem (fuse or something you mentioned), its a problem with your LabVIEW code. Maybe you can post your code to have a look at and see if we can find the issue.

Christian

[stitch182]

Sorry was on holidays.  I have added the code, but it was working is the thing I dont understand.

[Dennis_Knutson]

Looking at the properties of the DAQ Assistant, I only see a single physical channel defined - SCIMode4/ai0.

[stitch182]

Oops, Sorry  I sent the wrong one. This should be the right one

[Dennis_Knutson]

I don't have the same hardware but when I run your VI with my DAQ board, I see two different signals.

[stitch182]

So then what could be wrong when I change voltage on one graph the other graph shows the same signal. it is like it's not isolated. yet physically one is on 0 and the other on channel 4.

[Dennis_Knutson]

In the last VI you posted, you have the DAQ Assistant configured for channel 0 and channel 1. If you have nothing connected to channel 1, then what you are seeing is expected.

[Chris_K_]

Hi Stitch

The reason that you are seeing the same signal on channel 0 and channel 1 is because there is only one ADC and all the analog channels are multiplexed to that one ADC.  In your physical setup, channel 1 is floating, so when you read it, it is just reading the last value that the ADC read as it is not being set to any particular voltage level.  If you ground the differential pair of channel 1 then you will see your signal on channel 0 and nothing on channel 1.  This is known as ghosting, and you can read more about this at the following link.

Chris

[stitch182]

thanks, It seems it is ghosting, but One of the amplifiers in the chassis appeared to be malfunctioning. I took all of them out except one and it now seems to be working. Must of blown a fuse in one of the amplifiers, the pins all appear to be ok.