synchronization of DAQmx AI voltages to an external AI voltage timing signal

[physergo]

Hi, I'm trying to take an external synch analog signal from one source (Tekscan Versatek Synch Port) and use it as the trigger to record a set of voltage signals from another source (a Load Cell).  I would consider myself a novice with Labview, but am familiar with DAQ in general.

Here is the desciption of the timing signal from the Synch Port:

" Synch Output Type & Synch Polarity

The pulses can be used to synchronize an external device to each specific frame. The first pulse generated also indicates recording in general. Your electronics can start a process on the first pulse or do something frame specific on every pulse. In order to determine when to stop the external process, your electronics must sense a lack of pulses."

I would like Labview to read the load cell data each time a pulse is sent from the Hub.  Is there a way to do this?  I have a single USB-6216 and Labview 8.5.  If this isn't possible, I would settle for just way of triggering Labview to start recording load cell data when the hub first sends a signal. Thanks!

[Aaron_W.]

physergo,

Thank you for posting on the NI Forums. I am re-posting your previous post because some weird formatting got placed in your origional post. 

 _____________________________________

Hi, I'm trying to take an external synch analog signal from one source (Tekscan Versatek Synch Port) and use it as the trigger to record a set of voltage signals from another source (a Load Cell).  I would consider myself a novice with Labview, but am familiar with DAQ in general.

Here is the desciption of the timing signal from the Synch Port:

" Synch Output Type & Synch Polarity: The VersaTek hub outputs a short pulse 3 volts for about 2 microseconds at the beginning of the acquisition period for each frame. The circuit can source 8 Milli Amps, so it can drive CMOS circuitry. The VersaTek Hub Synch output is at ground between recordings. The synch signal starts in the off state, is turned on for a very brief period at the start of the frame and is turned off again. This cycle repeats at the next frame. This process starts when the record button is pressed and continues to the end of recording.

The pulses can be used to synchronize an external device to each specific frame. The first pulse generated also indicates recording in general. Your electronics can start a process on the first pulse or do something frame specific on every pulse. In order to determine when to stop the external process, your electronics must sense a lack of pulses."

I would like Labview to read the load cell data each time a pulse is sent from the Hub.  Is there a way to do this?  I have a single USB-6216 and Labview 8.5.  If this isn't possible, I would settle for just way of triggering Labview to start recording load cell data when the hub first sends a signal. Thanks!

[Aaron_W.]

physergo,

If you look at the NI Example Finder (Help >> Find Examples) you can search through the file structure in the middle go to "Hardware Input and Output >>  DAQmx >> Analog Measurements >> Voltage" If you find the Cont Acq&Graph Voltage- Int Clock - Analog Start. This example demonstrates how to being to acquire data based on a certain analog level being reached. You could have your program trigger off of the pulse from the hub. This should be a good starting point for your applications, let me know if you have other questions.