Synchronizing multiple 9172 chassis with 9237 in slave chassis

[sdouglas]

I have a LabVIEW application where I have 3 cDAQ-9172 chassis.  Each chassis has a 9401 module in slots 5 (or 6) for transmission/reception of master clock signal.  AI on chassis 1 is sampled at 50kS/s.  It passes it's sample clock to use as the timebase source for the other two chassis.  The other two chassis use a timebase divisor of 50 to yield sample rates of 1kS/s.  This worked fine until I entered a 9237 module into the mix in one of the slave chassis.

After adding the 9237 module, I get the following error:  Error -201097 occurred at DAQmx Control Task.vi:1  Possible reasons(s):  Measurements: Task contains physical channels on one or more devices that require you to specify the Sample Clock Rate.  Specify a Sample Clock Rate.  Device: cDAQ3  Task Name: AI2

I understand that the 9237 has a minimum sample rate of 1.613 kS/s when using an internal master timebase, but the documentation says it can achieve as low as 390.625 S/s when using an external master timebase.

Is there a way to sync multiple 9172 chassis with a 9237 in a slave chassis?

Thanks,

Scott

[ManLongAtNI]

Hi Scott,

Synchronizing multiple 9172 chassis with a 9237 in a slave is possible but it does come with some limitations due to the data rates for the 9237.  Please refer to the NI 9237 Operating Instructions and Specifications, Understanding NI 9237 Data Rates section for some documentation on the available sample rates.

Also, I believe the error you are seeing is the result of not setting the Sample Clock Rate for the slave device. This can be done using the property node. Also refer to the following ExampleCode as a basic template of how the setup should be executed.

CompactDAQ: Synchronized Analog Input Across Multiple cDAQ Chassis

Hope this helps!

Glenn

[sdouglas]

Hi Glenn,

Thanks for the info!  Although I was setting the Sample Clock Rate for the slave device, I think the real answer was setting the Sample Clock.Timebase.Rate property to 12800000 as shown in the example you provided.  Prior to that, I was setting the Sample Clock.TimebaseDivisor property for the slave devices.  I did get the example to work on a subset of my overall system, but I don't know if it will work with the rest of the devices in the slave chassis which are not Sigma-Delta devices generating their own internal master timebases.  So for now, I just moved the 9237 into the master chassis being sampled at 50 kHz.

Thanks again.

Scott