Send Message on Analog Trigger - timing details?

[Mawrob]

My ioBridge arrived and worked out-of-the-box in a few minutes.  What an excellent design!

I have an application where I wish to measure the analog voltage of a normally low intermittent pulse.  A varying amplitude between 1 and 5 volts that lasts for less than a second (typically a few hundred milliseconds) and that occurs once every 10 minutes - i.e. a periodic pulse with varying amplitude for each pulse.  Reading the manual I came across the following:

"Send Message on Analog Trigger: For this method of pushing data, a trigger and
reset value are set for the I/O channel’s analog input. When the analog input
reading reaches the trigger value, the analog data will be pushed from the
module. After the data is pushed, no more analog data will be sent until the
reset value is reached."

I may have missed it but I cannot find any information on the timing of the analog readings to tell if this should work?  How long after the trigger does the reading occur?  How long does pulse need to last etc?

Can you help?

[iobridge]

Welcome...

There is a trigger and reset value to allow the module to push the analog value to the server.

0 to 5v maps to 0 to 1023 raw analog values. I would try to figure out how much is considered a pulse and set a number appropriate to catch the pulse. Then set the reset below the trigger, to reset the checking of the trigger.

The sampling rate is very high. I will Jason comment on the exact resolution, but it's probably adequate for your project.

Have fun!

[jason]

The IO-204 is continuously reading the analog voltages and comparing them against any channel triggers you may have set.  The actual sampling rate varies depending on how many other things the module is doing (monitoring pin states, sending serial data, processing requests, filtering network traffic, etc).  But it would definitely pick up an event that was a few hundred milliseconds long.

As for resetting a trigger once it's happened...  if the voltage drops below the reset threshold immediately after the reading then the module will be ready the very next time it takes a reading.  This may be in the range of a few milliseconds.  This means that if you have a particularly noisy signal, you'll be getting unwanted triggers before and after the actual event.  If this is the case you may be able to use a simple RC filter to get the result you need.



   

[Mawrob]

Thanks for the response.  To confirm - does the ioBridge function as shown in the attached timing diagram where the ioBridge reading (ADC value read using the server or logged) follows the peak in a sample and hold manner?

Thanks again for your help.

[jason]

As you have it drawn, every time the signal drops below the reset line, the analog trigger will reset.   

[Mawrob]

Yes. That is what I had hoped.  I think I am beginning to realize that the analog trigger push is use to control a message event and not a sample event.

Thanks for the help.

[jason]

I think you've got it now.