Why can i NOT use "differential" on the MAX test panel for channels 8-16??

[Vr6Fidelity]

I have a USB-6218

This is a 32 channel device with 16 Differential inputs.

Why can't i use the MAX test panel to view any channel beyond AI-7 using the Differential setting? It shades out differential even though my device has this capability.

WHY???? 

[Dennis_Knutson]

When you use differential mode, only half of the channels are available. Channel 0 is paired with channel 8, channel 1 is paired with channel 9, ... ai7 with ai15. The next available channel after ai7 is ai16.

[Vr6Fidelity]

Thank you dennis for responding, your responses are the ones i value most as you are clearly the expert here.

But i have a 32 channel device, so i should have 16 Diffs available. I can only access 8 in diff mode. WHY?

[Dennis_Knutson]

I don't know why you can't view all channels in MAX. I've got version 8.3 but it apparently doesn't support a simulated 6218. When I go into the MAX test panels, I can view all channels and if I pick one of the differential pairs (i.e. ai10) it automatically switched to NRSE mode. Also, when I go to create a task, I can again view all channels. Where are you selecting diff mode? In the test panels or trying to create a task?

[Vr6Fidelity]

I am using MAX 4.1.0.3001 in conjunction with LV 8.0 and the USB-6218.

I go to MAX, Expand devices, expand MX devices, Right click on the USB-6218 (device2), and go to the test panels.

From there i am unable to view any differential pair beyond 8.

How am i supposed to Thru-Calibrate my equipment? Generally to achieve a valid calibration i use MAX itself to record the raw voltages the board "sees" as i apply known loads to the sensors.

The reason i need to check all this out is because DIFF pairs > 8 also are not working in my VI! Im am not sure if this is related or not.

[Ben]

16 17 and 18 do not work?

Confused,

Ben

[Vr6Fidelity]

16 RELATIVE to what? Am i supposed to measure potential from 16 to gnd, it's channel pair to ground and then do the math myself?

Where is NI on this topic?

[Vr6Fidelity]

And what about this? http://forums.ni.com/ni/board/message?board.id=170&message.id=216571

[johnsold]

The USB-6218 manual says the diff channels are 0..7, 16..23. Pages 65-66 of http://www.ni.com/pdf/manuals/371931a.pdf

Lynn