6229 DAQ Card: Problem if only one connector is connected

[benno_]

Hi!

I'm using a LABVIEW 6229 DAQ- Card to acquire signals. Unfortunately I only connected on of the Connectors of this card and left the other one unconnected (This means that one half of the analog inputs is connected to nothing). So far no problem 🙂 Unfortunately I'm still measuring signals on the analog input channles that are not wired to anything if I'm measuring signals on the analog input that are wired!?

The signals of this unwired analog inputs are quite similar to those of the connected ones..

If I only measure analog inputs that aren't wired to anything I see a voltage ramp or a constant voltage of -10V as I would expect. Any idea what could go wrong? All this seems a bit strange to me 🙂

Thanks for your help!

[Christian Mergl]

Why are you measuring at channels which are not connected to anything?

Christian

[benno_]

It happened accidentally because someone removed the cable from my setup without telling me and it took me some time to notice 🙂 And now I'm not sure if I can trust the measurements when I have connected all the channels.

[Christian Mergl]

Well, if you have nothing connected to an AI channel you just measure anything.

You will need to find a way that no one is able to disconnect the cables from the daq device.

Christian

[benno_]

Of course I measure anything, but why do i measure almost the same values as for the other channels? 0 or a voltage ramp is what I would expect for an unwired channel.

How can I be sure that the channels don't influence each other when I connected both connectors.

[Dennis_Knutson]

Expecting 0 with an unconnected channel is not correct. This subject has come up numerous times. Do a search for 'ghosting'.

[benno_]

But I also don't see ghosting at the unwired channels if i'm measuringsimultaneously
at the wired channels. Only if I'm measuring only unwired channels I see ghosting at that is what seems strange to me...

If I would always measure ghosting at the unwired channels everything would be fine 🙂