Multifunction DAQ

cancel
Showing results for 
Search instead for 
Did you mean: 

Non-time based scan rate

How do I acquire analog data with a scan rate based on a digital trigger and not based on time. I have two signals one analog and one digital. I want to acquire an analog data point every time the digital signal goes from high to low and from low to high.

Thank you.
0 Kudos
Message 1 of 4
(2,675 Views)
I don't think LabVIEW DAQ hardware supports triggering on both edges. It appears you have to trigger on one or the other.

The only thing that I can think of to try is to take your analog signal and split it into two different analog inputs. Use the example "Acq&Graph Voltage-Int Clk-Dig Start.vi". Insert it in a new vi twice. You will have to open it and modify the connector so the Physical Channel and Trigger Edge are inputs and the graph is the output. Then wire each one with a different analog input and trigger edge and run them sequentially. Hopefully it will run fast enough for you.
Randall Pursley
0 Kudos
Message 2 of 4
(2,663 Views)
Thank you. I think triggering just on one will be fine. In the matter of fact there are 494,676 ticks in the encoder revolution and it takes about 13 seconds to go full circle (every 0.000026s). My hardware can not acquire data that fast. I keep getting and error that the rate is too fast. I have a 6602 card and a BNC 2345. Do you know what the maximum acquisition rate for this hardware?
0 Kudos
Message 3 of 4
(2,657 Views)
Be sure that you are specifying a proper estimate for the rate of your external clock to your application. The default value may be too low, and the driver software needs this information in order to be prepared to handle the amount of data received.
0 Kudos
Message 4 of 4
(2,651 Views)