Creating Generating and Triggering a TTL Signal from an analog Input

[jzannoni]

Hello,

I am using a PCI 6251 DAQ with a BNC 2120 board. I am trying to trigger a camera based on a resistance signal. First I create and generate a 10 V DC signal through DAC0 on the BNC board (physical channel ao0) . This signal is sent out to a resistor that increases resistance with increasing pressure. A reisitance measurement is taken continuously and recorded throught the ACH0 connector on the board (physical channel ai0). As pressure is applied and resistance increases I would like to trigger the output of a TTL signal at a specified resistance. To generate a TTL signal can I just use the create step and set it do a voltage level equivalent to TTL on and then use the generate step to send this out? If so using the triggering tab in the generate step only gives me the option for APFI0 as the trigger source which is not my input channel. I have been messing around with this for a while and it has gotten incredibly frustrating and I feel like I am going in circles. Any help creating, generating, and triggering a TTL signal from this analog input in signal express would be greatly appreciated

[luda.mattski]

Hi jzannoni,

After looking into this, there are a few steps that might get you moving in the right direction.  To output your TTL signal, you'll have to create the signal through a "Create" step, then trigger and generate from there.  

The difficult part is going to be physically generating the output signal from the trigger input.  It would be easier to generate the TTL signal throughout the entirety of the test, and beginning datalogging or report generation with the trigger.  Is there anything in your hardware setup preventing you from doing this?  

Also, if you haven't looked into an explicit "Trigger" step, rather than configuring triggering within a DAQmx task, it offers a bit more functionality and customizability and may be worth checking out.