Can I give different exitation voltage to different input channels in SCXI 1520

[Akash Kumar]

Hi,

I am using SCXI 1520, I believe that it has an automatic gain adjustment. The problem is that I am using two channels out of the eight channels in the multiplexed mode. And the other six channels are just left opened. My problem is that when I receive the signal the out put of these two channels is very small and is very unstable whereas the output of the unconnectd channels is stable and is quite well amplified.

My question is that if I am not using the other six channels is it OK if I leave them open??, or if not that way is it possible that I give 0 exitation voltage to these six channels and and 10 V  to the two channels which I am using. ( bcoz exitation voltage is configurable but I dont know if for different channnels we can give different voltages)

What I see as a problem that the open circuited six channels generate very large input voltage compared to the two useful channels ( which receive signal from sensors in mv) and the gain adjusts itself according to these channels and and the useful channels remain unamplified.

Please tell me if my assumptions regarding SCXI 1520 are right or wrong??? and provide me with a solution so that I can obtain a good stable amplified signal  from the two useful channels.

Well the application software that I am using for the same is Labview.

Thanks,

Akash Kumar

[devchander]

Yes you can source different excitation Voltage on each in SCXI 1520

But before that, here is my thought

Why not specify only those two channels in your scan list?

Thus you can scan and display only those two channels

[Akash Kumar]

Well I have tried to scan only those two channels and it works well and here is the VI with this mail.

Now the problem that arises is that some times the VI works very well and I can see the exitation voltages on the two channels when I measure with voltmeter and sometimes it does not work at all because the exitation voltage do not appear.

I am quite confused sometimes the same VI works really well and sometimes it does not. Are there some other settings which are to be done??

Here is the VI.................

Akash KUMAR

[devchander]

Are you getting any error message when you cannot measure excitation voltage??

[Akash Kumar]

Hi,

I do not get any error message.

[devchander]

Sorry for late Reply, Akash

And does that also mean that you are not getting correct strain/Load( or whichever parameter you are measuring) readings on those channels when you voltmeter does not detect excitation output??