How to measure the pulse duration of a TTL signal using AI?

Question

Hi there.
I would like to know how to measure the pulse duration of a TTL signal using an Analog input.
These TTL signals comes from an ultrasonic sensor's output. The pulse width of the signal is
proportional to the distance of the object the sensor detected.
I have tried using the example "Measure Pulse Width.vi" which uses a counter to measure the
pulse duration instead. It provides me with correct results.
However, i will like to know how can i do it using the AI instead.
I tried it by using the example "Acq&Graph Voltage-Int Clk.vi" which i modified by including a
timing and transistion measurement vi. Pulse duration was selected as the output. A graph indicator was also added at the output of the pulse duration to monitor the incoming TTL signals.
However, everytime the TTL signals was detected on the graph indicator, the numeric indicator always produce a "zero" reading.
I have attached my vi for your reference.
Can anybody advice me what i have done wrongly?
Regard.
Attachments:
Acq&Graph Voltage-Int Clkv1.vi ‏190 KB

Answer 1

Hi Paul,
Today i tried using 2 different methods to read the pulse duration of my sensor signal.
Both methods use "Acq&Graph Voltage-IntClk" vi as a guide.
Method1:
Add a filter vi(lowpass/bandpass) and a timing and transition measurements vi.
Pulse duration is selected as the output. With some numeric conversion, a centimeter
reading indicator was created. However, the reading always remains as "zero"
Method2:
Add a Mask and Limit Testing vi and a timing and transition measurements vi.
By adjusting my upper and lower limits, i manage to "filter" a single pulse out from the actual signal.
However, like the earlier case, the cm reading still remains at "zero"
I have attached both the methods resulted waveforms for your reference.
Are there anything that you can advice on?
Regard.
Attachments:
Results_Waveforms.doc ‏141 KB