Simple DAQ assistant problem

[ctolson]

This is probably a simple fix that I am screwing up, but I can't get changes that I make in the DAQ assistant to apply.  Primarily changing the channels that the assistant reads, I will make the change, exit the assistant, and when I enter the assistant again the onlt connection found is ai/0.  Is there something that I can do to fix this?

Chris O.

[ctolson]

Also, when I run the program, i receive Error -50103, which is not in the error guide, I have attached my program to this message, any help would be greatly appreciated, I am still trying to figure LabView out.  The program is used to measure a voltage from a 4 wave gages, and create an 11 point calibration curve for each gage.  The user should be able to select a position, define the water depth, and click measure to measure the voltage.  Once 11 measurements have been taken and the user is satisfied with the results, the user will click a "calibration complete" button which will fit linear curves to the data and export the slope and intercept of the lines.  The secondary calibration listed assumes that the slope has already been measured, and calculates the intercept based on one iteration of data.  I am using a USB-6008 right now to figure the program out, and eventually will change to a higher quality DAQ board when the programs have been written successfully.

[Dennis_Knutson]

That error is most certainly in the error guide and is a very common error for beginners. You could have done a search for 50103 and found hundreds of messages with that as the subject. It is 'resource reserved' and means that you cannot have multiple tasks running at the same time on the same hardware resource. You can and should use a single task with multiple channels. Your wiring is pretty neat but seems an order of magnitude too complicated. When you run a DAQ Assistant with multiple channels, out of the dynamic data type, you can get either a 1D array of waveforms, or a 2D array of DBL.

I'm not sure exactly what you are trying to do but if you can explain that, I'm sure there is a much simpler way to manipulate the array.

[ctolson]

I figured there was an easier way to do it, but I just started using labview this summer and am still learning.  The program is used to calibrate wave gages (devices that sense the depth of water).  In order to calibrate the system, the user will take measurements at 11 different known depths (+5 to -5)  through two trials.  This will give a set of 11 averaged data points which will be used to make the curve. 

1.  The user enters the relative water depths (actual depth of the gage)
2.  The user selects a data point (+5, +4.. etc)
3.  The user will press a "measure" button which activates the DAQ device
4.  The data is stored in the array and the process is repeated until all 88 points have been measured (22 points per gage as the values need to be averaged)
5.  If there is any poor data, the user should be able to go back and remeasure those points to replace the bad ones.
6.  The user will press a "calibration complete" button and the slope and intercept will be calculated and stored in a text file.

-The secondary calibration only measures the intercept of the line of best fit after the slope has been determined and only requires one data point

I am assuming that the error I was getting means that I need to use only one DAQ assistant in the program.  If I fix that does the data taken from the board come in as an Array that can be divided into each channel?

Thank you

Chris O.

[Dennis_Knutson]

No matter whether you have one or multiple channels, you get dynamic data out of the DAQ Assistant. With the Convert From Dynamic Data, you can select either 1D Waveform or 2D DBL. You can use the Index Array function on either. With a waveform array, the first channel is the first element in the array. You could use the Get Waveform Components function to get the Y array or just perform the math on the waveform data type. I believe that with the 2D DBL array, each row is a separate channel.

[ctolson]

Thanks for the help!

Chris O.