CI Pulse Width

[Cuchulain]

I am trying to use the CI Pulse Width to measure the pulse width of a signal.  I am using a digital output to trigger a 555 monostable timer which sends a signal to a Parallax Ping, which in turn sends out a signal.  I am trying to use the counter on a NI USB 6008 DAQ to measure the pulse width of the signal coming back to the ping after reflecting off of an object, but I keep getting the error:

Possible reason(s):
Measurements: Selected physical channel does not support the measurement type required by the virtual channel you are creating.
Create a channel of a measurement type that is supported by the physical channel, or select a physical channel that supports the measurement type.

Property: CI.MeasType
You Have Requested: Pulse Width
You Can Select: Count Edges

Task Name: _unnamedTask<E6>

Is it possible for me to use the CI Pulse Width to measure the width of a external signal?

[ajmartin]

Hi,

I thought this was possible also, but it is not. Not with the USB-6008. The 6008 only counts pulses and then it only counts them on the falling edge.

I think for your application you could use the express VI "timing and transition measurments"  and bring the pulse in on an Analog in port. The Analog in on the USB-6008 can sample at 10kS/s . I am attaching 2 VI's that use the 6008 as the Daq and count pulse width.

I am sure the experts can inprove on these but both are working here on my bench.

Alan

[ajmartin]

Hello,

I would truly be interested in any constructive criticism of the VI's I attached to this thread. Both are working for my application of measuring a pulse width in MS. The duration is the width. I am confirming the freq and pulse width measurements  against a Tektronix TDS 1002 scope sampling at 1GS/s attached to the AI0 port the pulse is coming in on and the results are very close. I was going to try Hardware triggering later on today, not sure if that would help?

Thanks!

Alan

[Cuchulain]

Would you be able to upload these in 8.6 instead of 8.6.1?

[ajmartin]

Ok,

The second VI I changed anyway and now it has a trigger, at first glance it seems to make the measurement more accurate, but Im not sure yet. (didn't make it any worse) I also cleaned up the BD on the second VI.

Alan