real time and abview 8.2 and feedback responce times

[jimmyinCT]

i noticed there is a product called labview real time.

Ive never thought about this before, but what does it mean to not be real time?

How much slower is labview then other programmign langauges.

Ive been struggling for the last few months trying to get a simple feedback application to work.

Im supposed to be a simple feedback system that other people have done before, called a holographic interferometer.

Im copying the methods of the other people, but they did it in other programming languages.

the feedback signal, indicating phase shift comes in from 7 to 14 times a second, depending how many charts i have running.

yet, the output in responce to the feedback dosent seem to be wrokign correctly, almost as if its random or at times (with under shoot corrections)

this is allowing me to have gross accuracy, not not high precision work, ie, i can correct to + or - 20 degrees of 360 but i need +/-1 degree.

Here is an example.

I am trying to center a phase signal around 0 degrees phase.

When i apply to large of a correction, i get over shoot over the 0 degree line.

What is troubling me is that the over shoot has about 5 points in it, from one over shoot to the next, in a line.

The amount of over shoot per my computations is  a linear responce, so each should compensate the correct distance.

Im dumbfounded how this can be happening.

Each program iteration should be a different correction and there shoudl be only one point over shoot.

I have a very fast mechanical piezo controller running.

Infact, I had a researcer from another area send me his hardware from his wroking device, and im still getting these delays.

any thoughts would really be appreciated.

Message Edited by jimmyinCT on 03-05-2008 07:02 PM

Message Edited by jimmyinCT on 03-05-2008 07:03 PM

[BenjaminR]

Hi,

Most LabVIEW applications run on general-purpose operating systems like Microsoft Windows. Some LabVIEW applications require deterministic processing that non-real-time operating systems like Windows cannot guarantee. National Instruments created LabVIEW Real-Time to address the need for deterministic real-time performance using LabVIEW. LabVIEW Real-Time combines the ease of use of LabVIEW with the power of real-time systems so you can generate deterministic applications using graphical programming. These real-time applications run on LabVIEW Real-Time Series hardware, either plug-in data acquisition devices or networked LabVIEW Real-Time Series devices.

The LabVIEW Real-Time Development System runs on Windows, just like LabVIEW. You develop all code in this environment and down load real-time code to run embedded applications on a hardware target. Embedded LabVIEW Real-Time applications do not have a user interface, so they must have a host PC to generate the user interface. General-purpose operating systems can crash or hang, which causes programs to quit running. Because embedded LabVIEW Real-Time applications run on separate hardware, they do not stop executing if the host PC operating system crashes. If a crash occurs on the host PC operating system, the user interface is lost, and any communication between the embedded LabVIEW Real-Time application and the host PC ceases. However, embedded LabVIEW Real-Time applications continue to run. You can reboot the host PC without disrupting embedded LabVIEW Real-Time applications and re-establish communication between the host PC and LabVIEW Real-Time. You also can design your applications so you can retrieve any data that was collected on LabVIEW Real-Time Series hardware while the host PC was not in communication with the LabVIEW Real-Time application.