SR850 Data Reading Error...Help!

[BryanL]

I am reading data from SR850 through GPIB, and most of time I got the right data.  But sometimes I will get data that are not what I expected from its bus.  Is there a way or command to flush the bus before I take data?  Thanks in advance. Bryan

[Al M]

Bryan,

You can use the “ibsic” command to clear the bus of any information.  You can find documentation about that command here:

http://www.ni.com/support/gpib/max/ibic.htm

What type of unexpected data do you receive?  How are you communicating with your GPIB instrument (LabVIEW, LabWindows/CVI, Visual Basic, etc.)?

[BryanL]

Thank Al, I have not tried your suggestion yet, but do you think there is a device specific command? As the command you recommended resets the gpib borad instead of clear the buffer on SR850. Thanks again.

[BryanL]

Hi Al, I am using GPIB with LabView and the error I got are data that should have read out by a previous GPIB read command to the same instrument (i.e. SR850).

[Al M]

Bryan,

Did the previous read terminate early?  That may be why there is still data in the buffer.  How are you terminating your communications?  If you have it set on bytes to read you could always increase this number to ensure that you are reading all of your available data.

Al M.

Applications Engineering

National Instruments

[BryanL]

Hi, I am using 400 bytes read buffer which I believe is big enough for the data to read (just a single voltage number). Somehow I always got data that are two data points too early.  I need a way to clear the buffer of the instrument so that I will read current data......help...help.

[Al M]

Byran,

I found the following information on the SR850 online manual:

REST

The REST command resets a scan. The REST command can be sent at any time - any scan in progress, paused or not, will be reset.  This command will erase the data buffer.  All swept parameters are reset to their start values.

http:/www.thinksrs.com/downloads/PDFs/Manuals/SR850m.pdf

 

Page 6-22

Al M.

Applications Engineering

National Instruments

[BryanL]

Hi Al,

Thank you so much for your help.  I modified my GPIB termination mode yesterday based on your suggestions and I was not seeing the errors later. Since the error appears only occationally, I dont know if the problem has solved.  With the new command you found, I believe I am in very good shape.  Thanks again.

Bryan.