Need the fastest update from analog Measurement (DAQ) for controlling sensors that give direct feedback to motion control. Seems board limited? Fastest is about 1.5 milliseconds, can I go faster?

[fiberpunk]

I have designed a sensor system for my linear motor stages that sends relative location back via an analog signal. My positioning speed is dependent on how fast I can read my sensor. Currently, my best implementation updates the software every 1.5 milliseconds. I would like to increase this by at least an order of magnitude. My DAQ is a 1600 series with 200K sample rate, so that is not my limit, my limit is to get it into my software. Any ideas?

[Ben]

Hi Fiberpunk,

If you are using LabVIEW-RT, you can get about 40 KHz out of a harware timed loop.

If you are using windows, you cannot specify precisely the update rates.

If determinism is not an issue, windows would work, but you have probably found the limit for your machine.

Ben

[Filipe A.]

Hello;

To acquire data on a point by point basis will limit the sampling rate to how fast the OS can handle your process.

To speed up that rate, you will need to use buffering. That technique allows one to acquire data as fast as the hardware limit is, and store those points in a buffer.

You didn't tell what programming language you are using, but regardless the language, there are good examples showing how to program a buffered acquisition with your board (C:\Program Files\National Instruments\NI-DAQ\examples\ or in Labview Search Examples->I/O Interfaces->Data Acquisition->Analog Input->Continuous Analog Input).

Hope this helps.
Filipe A.
Applications Engineer
National Instruments