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Hardware to Measure 5µs TTL Rising Time



I have a cRio 9074, with 1 NI9401 for cRio. I need to measure the rising time (10%~90%) of a TTL signal, this signal has a frequency of 2kHZ and an expected 5µs rising time.

My question is how can I, or if it is possible to measure  this rising time using an I/O module for cRio?

If is not possible to use an cRio system, which hardware from NI is capable of doing it? Preferably a NI PCIe Card.


Thanks in advance.


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To measure rise time you need an analog input module. A digital input device will merely tell you whether the input signal is above or below the logic threshold at the instant that it is read. You need to locate the 10% and 90% points on the waveform to determine the rise time.


If the rising edge is a linear ramp, then you would need to get about 10 points in the 5 us.  That translates to a 2 MHz sampling rate. At a quick glance I did not see a Compact DAQ module that fast. The PCIe-6361 and PCIe-6363 can sample at 2 MS/s.  I think those are multiplexed A/D devices so they cna only get that sample rate on one channel. Sampling multiple channels reduces the rate.



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Hi Johnsold,


Yeah, I know I need a Analogue card to do the job. My question was if I could use an I/o analogue module for cRio for it, I didn't find until now any that could do it or if there could be implemented an workaround using the cRio FPGA and an analogue module.


I've already looked to the PCIe-6361 card, but I would prefer to use cRio.  


Is there any NI digitalizer that could work with cRio?


Thanks in advance.


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Hi Johnsold,


First thanks for your reply.

Like I mentioned I have a cRio 9074 and 2 NI9401.

I have to more questions that need to clarify:


1 - Is it possible  to measure the width, frequency, duty cycle using the NI 9401 or do I still have to use an analog input?

2 - How can I connect an encoder to the NI 9401 and the cRio System (a slot that could be used as a counter) so I could calculate the angular velocity and angular movement of an encoder?


Thanks in advance.


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