Measre pulse width of a very narrow pulse

[GNS]

hi,
I have one query.
I have to measure pulse width of a very narrow pulse , may be it is 0.1 ms
or less . I m using the VI , which I m sending u with an attachment
here....I m having doubt that this VI is able to measure the required pulse
with. Sometimes It is giving wrong values too. So Plz suggest some solution
which may fulfill my requirement.
I need the answer at the earliest. I'll be grateful to u.

Regards.
GNS

[rgharrison]

Hi GNS,

If you are using an E Series card or a 660x card, you should have no problem making a fairly accurate pulse width measurement. When performing pulse width measurements, your maximum error will be +/- 1 pulse of your timebase (assuming the crystal oscillator error is negligible). If you are using a 20MHz timebase, you will have a measurement resolution of 50ns. 2000 pulses would occur to measure a 0.1ms signal. Your maximum measurement error will be roughly 1/2000.

If you are trying to measure a mechanical source, there could be "bouncing" which will affect your effective pulse width. This is a situation in which you have several small glitches that occur before and after your main pulse. This is typical with push buttons etc. Anyway, these gl
itches could seriously alter your measurement.

The best way to test your measurement system is to use 1 of your counters to generate a 0.1ms pulse and have the other counter measure it with it's maximum timebase. This will indicate your accuracy.

Hope that helps. Have a good day.

Ron

[GNS]

Hi
Thanks for the reply.

If u plz look into the code, which I sent u with the attachment, u may find that there is a while loop where "armend" is passed as attribute ID to "Counter Get Attribute.vi" . what this action is and what activity is performed here? Does this action affect any accuracy if the measurement of a very narrow pulse is required. There is delay also given in this loop, don't u think that while the execution is waiting for this much time, if the pulse for measurement is given during this only , it will ignore it or may not measure it accurately? Kindly help me in this regard. This is a very critical measuremnt in my application. Any error may lead to huge data loss.

regards
GNS

[rgharrison]

Hi GNS,

The action that is performed is a query of the counter to see if it is busy. If it is in the middle of an application, it will return with a true value for "is armed". This function and the delay do not affect the outcome of your result. Therefore your data will be accurate. You don't have to worry about that function. Hope that helps. Have a good day.

Ron