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2 very simple questions about 6225 PCI card

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Hi everyone,



I am using for the first time a 6225 PCI card (80 analg inputs). This card is linked to two SCB-68 bloc junctions and my purpose is to use it to acquire 40 différential signals. Using the DAQ assistant I have come up to these conclusions :


1)      The first 8 of my 40 différential inputs go onto the first bloc junction?

2)      On bloc junction n°1 for each differential signal I need to put a 10 Kohms biais resistance between each AIGrnd and the V(-) of the signal. This is what I have done with other 622X cards. In order to do this with bloc n°2 too, I only have pin n°22, 9 and 43 free to use for all my 32 signal. Is this correct?


I know these are 2 very basic questions but  if somebody could just answer them for confirmation it would be great.


Thanks a lot,





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Accepted by topic author User_1979



1) The first 8 inputs go onto the 1st bloc junction as this pdf for connector 0 shows.  For the last pin on the connector 1 you will find the information in the screenshot below :


connector 1.PNG




































2) Depending on your source impedance, you should connect your source as described in figure 4-5 :


Differential Connections for Floating Signal Sources with.PNG

Or 4-6 of M-series user manual (page 4-15 to 4-18, thus, with a coupled bias resistor also between the positive lead of the source and AI GND).


Thereafter if you have some noise problem , you could follow these documents:

How Do I Eliminate Ghosting From My Measurements?

Decreasing the Source Impedance of an Analog Input Signal

Using a Unity Gain Buffer (Voltage Follower) with a DAQ Device

I hope this helps.



Message Edité par Steve M. le 11-01-2010 11:48 AM
Steve M.
Message 2 of 5
Dear Steve,
Thank you very much for your quick and relevant answer, specially for the jumpers setting.
- Could you confirm that if there isn't a .pdf card (6221-6224 for instance) in the attachments files at the bottom of this page (, it means the SCB-68 M series conn. 0 and 1 .pdf should be used ?

- I am sorry but I don't understand what is special about the last pin on connector 1 ?



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In the link you attached, the pdf named "SCB-68 M Series conn 1.pdf" is for the other M series card which use 2 connectors like 6229 & 6224. For the 6225 & 6255 card you have a psecial pdf for it  (SCB-68 6225 & 6255 conn 1.pdf) because these cards have 80 analog inputs. So, you can see that regarding the other M series cards the connector 0 is the same, the difference is only for the last 64 inputs on the connector 1.


For information, you can access these pinouts of your card from the NI-DAQmx Device Terminals help file that is installed with DAQmx. A quick way to access this file with the exact pinout you need is from Measurement and Automation Explorer (MAX). In MAX under Devices and Interfaces, right-click on your device and select Device Pinouts. This will open the help document, as well as go directly to the pinout diagrams for that particular device.





Message Edité par Steve M. le 12-01-2010 09:57 AM
Steve M.
Message 4 of 5

Hi Steve,


Thanks again for all this information.





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