I have attached my VI which was made with Labview 2010. The VI uses DAQ assistant to read voltage levels on 4 different pins. The DAQ is a USB 6009. This DAQ has 8 analog inputs. They are split into 4 pairs of 2, e.g. A0+, A0-, A1+, A1- etc. I have wired all 4 pairs to 4 magnetometers.I am able to read the magnetic field strengths and display on graph. If the level on the second magnetometer (only the second for now as its just in a test phase) goes above 250 or below -250, it triggers a light which turns red, using one of the analog outputs on the USB 6009. If it stays within the limits, it will be green (using the other analog output)This so far works perfectly fine. Where I started having issues was in the current implementation of the VI which uses a second while loop. This while loop triggers when the magnetometers go out of their limit of 250. At this point, the light will stay red, and a user must push a button which connects digital I/O pins 17 and 18, which triggers the 'STOP' function of this inner while loop.If I wave a magnet near the magnetometer, get the light to turn red, and wait more than 5 seconds, push the button, this DAQ Assistant error appears. However, if I make the light go red and immediately push the button within say 2-3 seconds, the VI works perfectly fine! Do you know why waiting inside that inner while loop for too long causes the error?The intention of the VI is that if the magnetic field level near the magnetometers goes above a certain threshold, the light turns red, and a user must physically push a button to turn it back to green. If the levels do not go above the threshold they are green (i.e. they are normally green) Error -200279 occured at VIname.vi:Instance:0:1 - Attempted to read samples that are no longer available. The request sample was previously available, but has since been overwritten.Increasing the buffer size, reading the data more frequently or requesting a fixed number of samples to read instead of reading all available samples might correct the problem.Property: RelativeToCorresponding Value: Current Read Position Property: Offset Corresponding Value: 0 Task Name:_unnamedTask<233AF8>EDIT: Another issue is that when the program enters this 'inner' while loop, the code outside the inner while loop (but still in the outer while loop) does not run. For example, the DAQ Assistant acquiring magnetometer levels and graphs showing levels of magnetometers. Is there a way to implement my program without an inner while loop which causes this behaviour and may also fix the program crashing too?

Hi lorc, @lorc34 wrote: In my mind it's possible to do this for example if it was python or similar: Color=0 While() GetLevel() If level > 250 or < -250: Color=1 If Color=1 SetColor(Red) Elseif Color=0 SetColor(Green) If(ButtonPushed): Color=0 In your "python" example there is only one while() loop, so why are there two loops in your LabVIEW VI? It seems to me that the variable "Color" should be a boolean with values false/true instead of an integer 0/1… This would be a LabVIEW replacement for your python snippet: (It is not exactly the same, but very similar…)

LabVIEW

Can anyone help me with this DAQ assistant error. Error -200279 occured - Attempted to read samples that are no longer available.

Solved!

More rules of thumb for you:

To digitize a pure sine wave and have the sequence of values *look* more-or-less look like a sine wave, it's often recommended to have a sample rate at least 10x the sine wave frequency with 20x being preferred.

So if you sample at 10 Hz, you can get a reasonable time-domain representation of a sine wave that's less than 1 Hz.

Your next problem may come from how you write your software to process your data and make decisions. If you're trying to characterize the *amplitude* of a sine wave, you'd better capture at least 1 full period of it, which requires a dataset representing at least 1 second. Whether you read that dataset all at once or whether you read a little at a time and accumulate, you need that >= 1 sec dataset to evaluate amplitude.

As to LV 2010, I'd venture that you're fine until that particular PC dies. I don't have the whole matrix of compatibility charts at my fingertips, but LV 2010 will constrain you to older versions of DAQmx which will in turn constrain you to older Windows OS versions and possibly older DAQ devices.

There are different pain points when trying to upgrade such old systems incrementally -- it's often better to do things all at once.

With a new PC, Windows OS, and LabVIEW version your LV 2010 code will likely convert pretty smoothly. Most often any DAQmx code will work out fine too if you are using a common DAQ device. You may be able to keep using the same device, especially if it's PCIe or USB.

-Kevin P

ALERT! LabVIEW's subscription-only policy coming to an end (finally!). Permanent license pricing remains WIP. Tread carefully.