Why is the thermocouple reading wrong?

Situation:
I have the PCI-6221 interface board with an TBX-68 connector block directly connected with T-Type thermocouples. Thus the temperature reading should only be between 0 and 400°C. I made a program to read 6 thermocouple channels.
Problem:
I only connected the first two channels. These are reading properly but the others give me signals which are completely nonsense! Like 600°C and so on. Do I need to install an condensator (like 10µF) at the conector block between the thermocouple contacts? How can I get a constant 0°C out of not contacted thermocouple channels?
Greets
Attachments:
Thermocouples reader1.jpg ‏203 KB

The nonsense it because of the open terminals, and the bias currents off the inputs.
If you shortcut the inputs you should read the board/cold junction/room temperature.
Or wire a 1M from AI+ to 5V and another from AI- to GND (diff mode assumed). That would give a max/overrange reading, but might have some influence to the other channels due to crosstalk but worth a try.
The clean way is to disable the readings by software.
Greetings from Germany
Henrik
LV since v3.1
“ground” is a convenient fantasy
'˙˙˙˙uıɐƃɐ lɐıp puɐ °06 ǝuoɥd ɹnoʎ uɹnʇ ǝsɐǝld 'ʎɹɐuıƃɐɯı sı pǝlɐıp ǝʌɐɥ noʎ ɹǝqɯnu ǝɥʇ'

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I'm using Labview 8.5.1. and NI DAQmx 8.6 and I'm wondering what the DAQmx Read VI is actually doing.
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Attachments:
daqmxAcquisitionTime.PNG ‏20 KB

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Why is the thermocouple reading wrong?

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