Compact DAQ 9215 BNC module -- Error code -200278 occured at DAQmx read

[hkhiroya]

   
Hi,

I am trying to read data from a sensor giving an output between +/- 300mv. It is connected to the 9215 BNC module on the Compact DAQ chassis. When i try to acquire any number of samples at any frequency it comes up with an error message at the end (-200278). I have attached the screenshot of the error message.

The program displays information in realtime in a waveform chart on the front panel as the  samples are acquired and also writes them onto a lvm file. I have also attached the vi of the program.

Please help me as i cannot solve this problem. All help will be appreciated.

Thanks
Harshil

[Wayne.C]

Try this.  You will note that I have modified how the iteration count is compared to the number of samples.  Remember, the iteration count starts at 0 and not 1.

[hkhiroya]

Hi,

Thanks alot for the help. Now the problem I am having is that if I specfy a large sampling rate the display is very slow as it is acquiring at a much higher pace than what it can right. This is because the file written to is inside the while loop. If I put the write file function outside the while loop then it only writes the last value.

Please help on how to get round this.

regards
Harshil

[hkhiroya]

Hi,

Thanks alot for the help. Now the problem I am having is that if I specfy a large sampling rate the display is very slow as it is acquiring at a much higher pace than what it can right. This is because the file written to is inside the while loop. If I put the write file function outside the while loop then it only writes the last value.

Please help on how to get round this.

regards
Harshil

[Wayne.C]

Suggest you use a shift register and build an array of data in the while loop.  Then you can write the entire array of data to the file after the while loop has completed running.

[hkhiroya]

Hi,

Im sorry but im quite new to labview can please slightly explain more or elaborate more on how to use the shift register and the build array function.

regards
harshil

[Wayne.C]

There are many examples included with LabView that use shift registers and arrays.  Help>Find Examples

These are also covered in the LabView Help.

[hkhiroya]

Hi,

Thanks for the help. I have tried to use arrays to store the data before i write to the file. The problem is when it writes at the end, the format changes and i do not get the channel name and the dt value (time interval between samples).

Also if i select more than two channels than i do not get two colums in the output file but one column with both the values of the channels one after the other and thus becomes very hard to make where one channel ends the other begins.

Please help on how to get round this.

Harshil

[Wayne.C]

Try this.

[hkhiroya]

Hi,

Thanks for the help. I had initially done it without a while loop but the problem with this method is that the waveform is not updated constantly while the inputs come in (real time). The graph in the waveform chart will be displayed at the end. Thus I can't monitor the inputs as they come in.

Please help.

regards
Harshil