Converting a usb6008 cumulative count output to a speed measurement

[JamesBM]

Hi,

I am new to the data logging game so I would appeciate some assistance from some seasoned veterans 🙂  I have connected a speedometer to the PF10 and GND inputs to the USB 6008.  The speedometer generates a square wave who's frequency fluctuates as speed fluctuates.  I know the scaling factor (SF) between distance and number of pulses so with this I want to calculate 'instantaneous' speed in real time from the logger. 

So far I have managed to get SignalExpressLE to give me a cumulative count of falling edges of the square wave but there does not seem to be a way to manipulate this data in real time.  Does anyone know a way of linking the SignalExpressLE output to Excel in real time?

Alternatively I thought of using C# to talk directly to the DAQmx to perform the conversion.  My idea is as follows:

counter sample rate = 10Hz

'instantaneous' speed output = 1Hz

speed calculation = 'instantaneous' speed @ t + 1 sec = SF*((cumulative count at t + 2sec) - (cumulative count at tsec))

Can anyone direct me to some example code which performs a smilar operation?

Oh and one more thing - I'm using a digital input and 2 x analogue inputs at the same time as taking the speed measurement.  If I do use C# to talk to the DAQmx can I simultaneously use SignalExpressLE to process the other inputs or will have to do everything in C#?

Thanks,

James

[Sarah_Coleman_NIUK]

Hi James,

You can have another application using the DIO and AI lines at the same time as C# is using the counter as they don't use any of the same resources.

Are you looking for example code to set up a counter measurement with DAQmx in C#? You should be able to use one of the ones that gets installed with DAQmx. They're located at C:\Program Files\National Instruments\NI-DAQ\Examples\VisualC\Ctr.