How to simultanoursly acquire data through two channels through GPIB write and read.

[Yaglaser]

I can acquired data from two channels from Boxcar, and GPIB Write and GPIB read one channel first and then to use the same way to get data from another channel. This program works perfectly, When I tried to acquire data from both channels simultanously through GPIB, problem happened. The error window showed like followings:

Error 6 occured at GPIB Read

Possible reason(s):

Labview: Generic file I/O error

NI-488: I/O operation aborted

Because the function of two channel is same, so I set mode (2), and byte count (20) for GPIB Read for both of them.

My question is how to correct it, or how to built a labview program to get data simultanously from channels, because one data in one channel is for reference, and another channel for measuring sample, so acuquiring data at the same time is very important.

Thanks

[Dennis_Knutson]

You can't issue two commands simultaneously. That's not the way GPIB instruments or the bus works. Some instruments have a comand that allow you to retrieve multiple readings with a single command but if your instrument doesn't have such a command, that's might be okay.. If you can set up the instrument to take both readings at the same time, then it doesn't matter if you transfer one reading right after another or wait days between transferring the second measurement. It's getting the actual measurements to be be performed simultaneously that's important. Yuo don't mention the make and model of the instrument so I'm going to have to be a bit generic in my comments. Look to see if the instrument has some sort of triggering mechanism so that you can arm both channels and the instrument will sit there waiting for the trigger condition. When triggered, the instrument will take readings on both channels and the results can be retrieved at your leisure. Some instruments have hardware triggering, software triggering, or both.

[Yaglaser]

Yes, just like what you said. My instrument has trigger signal and there are 8 input channel, From theory, I should readout the values of eight channel. Could you show me a example. I know tha oscilloscope has also the same function to get data from multiple channel at the same time, I can't figure it out, though there is subVI about trigger and scaning.

Thanks.

My instrument is SR 245.