SC-2040 T/H missing as assessory for DAQmx

[cpede]

We changed our translation driver to support the new DAQmx driver model. Now some of our customer comes back and say that the SC-2040 T/H board is not available as assessory for their DAQmx boards. Is this really true, and how do we overcome this problem?

-cpede

[cpede]

Any idea how to get the MIO-16XE-10 board to work with the SC-2040 assessory box?

-cpede

[cpede]

What can we do to get this to work!!

[Laura F.]

Hello cpede,

I see the SC 2040 as an accessory that I can choose for an MIO board in DAQmx.  The only difference is that it is called the SC 2040, and not the SC 2040 T/H.  Do you think that this is causing confusion for your customers?

Thanks,

Laura

[cpede]

Thanks for your answer. What version of DAQmx are you using?

And what does the information on this page then means?
http://digital.ni.com/public.nsf/allkb/B50A1CA411D90EAD86256F1E0065FDC0

And this?
http://www.ni.com/support/daq/versions_sc_accessories.htm

Can the SC-2040 be controlled programmably from DAQmx.

-cpede

[cpede]

I'm running DAQmx v7.5, can that be the cause??

-cpede

[Laura F.]

Hello cpede,

I am using NI-DAQmx 8.0.  I am not sure why those two documents say that the accessory can be used with Traditional DAQ only.  I will get back to you with more concrete information.

Regards,

Laura

[Laura F.]

Hello cpede,

I have investigated this a little further, and the two documents you referenced are correct.  Even though you can add the SC 2040 as an accessory in MAX with NI-DAQmx 8.0, you do not get access to its functionality.  In order to use this accessory with DAQmx, you will need to provide the signal for the track and hold functionality to PFI7 according to the user manual. 

It does not need to be listed as an accessory in MAX since it basically provides straight through connections to analog lines and you can provide the other signals it needs in your program.  For example, to provide the track and hold signal, you can use the DAQmx Export Signal VI to export the Sample Clock to PFI7.  This signal needs to stay high for the duration of the acquisition for all channels so if it doesn't in your application, you may need to use the counter to generate a sample clock instead.  You can control the duty cycle of counter pulses, but you cannot change the duration of the internal Sample Clock pulse. 

I apologize about the confusion,

Laura

[cpede]

Hi, Thanks for the answer.

I'm using C++, but I guess I can find a way to export the Sample Clock to the PFI7.

Just to understand, the device is in the accessories but does not do anything.

I do a very simple measurement sampling at a certain frequency a number of channels. The sample clock defines the time between scans?
Meaning that this is high while the channels are scanned, and goes low between measurements.

Is exporting this signal the only thing I need to do?

-cpede

[Laura F.]

Hello cpede,

The C function has a very similar name to the LabVIEW VI: DAQmxExportSignal. 

When you configure this accessory using Traditional DAQ, you are able to set such things like the gain and the PFI7 line has a signal automatically routed to control the 2040.   None of these things occur when specifying this accessory in DAQmx.

There is a nice section in the NI-DAQmx Help installed at Start >> Programs >> National Instruments >> NI-DAQ about clocks in general (search for "clocks").   For each tick of the sample clock, one sample per channel is acquired.  The multiplexing between these channels is controlled by the convert clock.  The sample clock pulse has a small pulse width so it may or may not stay high long enough for the samples to be acquired on all channels.  If it does not, I would recommend using a counter as your AI sample clock so that you can configure the pulse width of the pulses.  To do this, setup a pulse train generation on a counter and then use the internal output of this counter as your sample clock source.  Make sure that the counter task is started before the analog input task. 

Thanks,

Laura