analog trigger?

[Murph]

Let's see if I can explain what I am aiming to achieve. I am acquiring a 0-50mv signal from a gas detector. The baseline of my source moves around quite a bit. Sometime it is up around 8mv sometimes around -1mv. The background is about 1.5mv. I am using a USB-6008 for now on AI0, single sample, +/-1v, diff.

Once I put a sample into my detector the voltage rises and can be read easily. It ramps up quickly and has a slow decay.

My question is sort of 2 parts.

The attached png demonstrates what my signal looks like as well as what I need to do with it after. Due to the nature of what I am doing I need to calculate the area under the acquired curve. This is calculated using summed averages/time.

1. Right now I start the acquisition manually and use a variable to set the baseline as I do not want the background to be part of the calculated area. I want to be able to get Labview to start acquiring when it sees a delta change on the input signal. This way anything equal or above that trigger point will be used in the calculation. Right now I just run it on a user selected time period but need it to start at a trigger point and stop acquiring when the signal returns to that point on the downslope.

Mike

[John_P1]

Hi Murph,

The 6008 does not have analog triggering capabilities, but you should be able to implement what you want in software.  Try starting with this example:

Continuous Acquisition with a Software Analog Start Trigger

Best Regards,