Triggering an Digital Line Out on a Trigger

[Dane S.]

Hello,
I'm relatively new to Signal Express 3.0 so please bear with me

Want I am trying to do is to
- Produce an High digital out, when data from any of seven sensors increases a specified value. (3 thermocouples, 2 Load Cells, and 2 Pressure Transducers)

What I have been able to do
- I can create alarms for each of my sensors and then have them trigger at some amplitude and I can have each one output a digital out on its own line

What I don't understand
- I was thinking this software trigger option under alarms but I couldn't figure out how to link this to my digital out, which also has an option called Programmatic input that I don't understand

Any help would be appreciated I've spent hours on Google and going through example files and tutorials but to no avail.

[aNIta B]

Hi Dane,

        I'm curious if you've tried creating a triggering step, rather than using the alarms.  By going to Add Step»Execution Control»Trigger, you should have more control of your program than using alarms.  If you haven't checked out THIS KB, please do- because it sounds like it addresses your issue pretty well.  Let me know if there are other specific questions you run into, and have a great weekend!

Message Edited by aNIta B on 03-13-2009 12:22 PM

[Dane S.]

Thanks for the response aNlta B but I don't think triggers will do quite what I need them to do.

    The problem with the triggering is it waits for acqusition to be over to my understanding, the reason I used alarms is because I have an external PLC (digital I/O only) that controls my device, and the purpose of the alarms on the sensors was if the pressure, temperature, or load ever exceeded what I've deemed safe it would send some signal to my PLC which is programmed to stop testing and intiate emergency procedures. (Don't know if this helps but my device is a static test of a hybrid rocket, for my university rocket team). If there is a way to go about this it would be alot of help!!

[aNIta B]

Hi Dane,

         While triggering doesn't really wait for an aquisition to be done ( the trigger will occur whenever the trigger condition is reached), you're right in thinking that you won't be able to trigger one of your other devices using a trigger in SignalExpress (the triggering function would be useful if you were using one device that you wanted to stop or start aquiring when that specific device reached a particular value). However, the fact that you are using an external PLC changes things (sorry, I should have taken note of that sooner).  While you can import data that meets OPC specifications, you won't be able to write to your PLC with an alarm (if you were using simple DI/O device- you could simply write a digital high or low to that device).  To do this, you would need LabVIEW, and ideally the Datalogging and Supervisory Control Module, as per THIS KB.  Let me know if you have more questions!