dual channel digital input speed

[nicola]

I have one proximity with dual channel FPDI.
I would like by program the speed change status of the proximity.
With the function read value i have the boolean status of proximity.
What is the best system for keep the frequency?
If is possible an example code.
Thank's Nicola

[Chad E]

Hi Nicola,

NI has FieldPoint counter modules that would perform this operation. For example, you could use the FP-CTR-502.

Also, here is a link to a NI Dev Zone document on using proximity sensors:

http://zone.ni.com/devzone/conceptd.nsf/webmain/516B2E072D755E0C86256CF6007B5066?opendocument

[nicola]

Hi chadevans,
My problem is: I have a dual channel FP-DI (BOOLEAN INPUT) and i must create the application with this module.
The accuracy is not request but i would like build a polling cicle :take the status input,and perform the speed.
It is possible ?
Thank's Nicola

[Chad E]

Hi Nicola,

Maybe, if you use LabVIEW RT on a FieldPoint RT Network module, you could get this to work. But, your digital signal would have to change no faster than about 100 Hz or you could miss changes (the TB-10 update rate is between 1.2 and 7.7 mS depending on what other dual channel modules are installed).

There is no way to do this on a Windows machine, because there is no way to know for sure how long a read is going to take. Therefore, there is no way to calculate the time between changes or to be certain that you detect all of the changes.

Regards,

Chad Evans

[nicola]

Hi Chadevans,
I'm know that's a no better solution, but the signal is <1Hz to change. For this i have think is possible to keep the speed of change.
The system is mounted in the client structure.
Nicola

[Alberto]

Hi Nicola,
Since accuracy is not an issue, I attach a sample vi that returns the time elapsed between the change of state of a push button. It is toggled by the change of state from False to True.
If you do a continuous read of the state of the digital input, you can use this method do determine the time between status change (thus speed).

[nicola]

Thank you Alberto i have in my application a vi similar of you proposal.I think i do buy a counter because the speed calculated is very bud.
Nicola.