External Clock as Timebase (NI PCI-6122)

[thunder_]

I am using the PCI-6122 card and want to provide a very accurate external clock (preferably 10 MHz) as a timebase. I tried to connect my external clock signal to PFI-8 and then to internally route PFI-8 to RTSI-7 but this didn't work. I am using only one card and thus have no rtsi cable beeing installed.

Can you help me setting up the card to use my external clock?

[Doug_L._Bear]

You should be able to just use the signal on PFI-8 as the clock source, without any routing to RTSI lines.  I would look at the example Acq&Graph Voltage-Ext Clk.vi.  It can be found in the Example Finder by going to Help»Find Examples... and in the browse tab selecting Hardware Input and Output»DAQmx»Analog Measurement»Voltage.

Doug F

Applications Engineer

National Instruments

[thunder_]

Thank you for the answer. However, the example you are pointing me to is providing an external sampling clock, which will set my actual samling rate. I am wondering if I can just apply a 10MHz standard as external clock (replacing the cards onboard clock) and then choose with the software whatever sampling rate I want to use?

[kikiduu]

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thunder_ wrote:

I am wondering if I can just apply a 10MHz standard as external clock (replacing the cards onboard clock) and then choose with the software whatever sampling rate I want to use?

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May be you can try using the 'SampleClock>>Timebase>>Source' Property available with the DAQmx Timing Property Node.

Also internally 6122 may be using a 10/20MHz timebase. Is there any issue that you faced becasue of which you want to go for an external timebase?

Message Edited by kikiduu on 02-09-2009 01:42 AM

[kikiduu]

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kikiduu wrote: 

May be you can try using the 'SampleClock>>Timebase>>Source' Property available with the DAQmx Timing Property Node.

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Hey actually there are no routes available to sampleClockTimebase from PFI or RTSI lines. So whatever I suggested is not going to help you. So only thing that you can do is use external sampling clock. Also you need not do any routing to RTSI lines if you use PFI 7, 8 or 9.

[thunder_ · Accepted solution]

Thank you for your help. It seems that there is no way around and I have to "spend" an extra signal generator (locked to my 10MHz reference) to provide a sample clock, locked to my experiment.