LabVIEW SignalExpress stops recording after 20 hours

[Maksim]

Hi,

I'm recording 8 channel voltage using SignalExpress 2010 with USB 6221 board. I have an 8-channel recording step, a 4-channel ToAscii step and another 4-channel ToAscii step. The ToAscii goes to a USB external hard drive. I've been trying to record for 72 hours straight. I've tried 3 computers with the following results:

• Windows XP - 4GB- Core 2 Duo:  Computer is unresponsive after 48 hours. Have to force restart
• Windows XP - 4GB- Core 2 Duo. Records for 20 hours then SignalExpress stops writing to disk. The traces on SignalExpress stop changing. But the External hard drive is still spinning.
• Windows 7 - SI 2009: Same as the 2nd situation except after one hour.

I need it to be stable for 72 hours.

[R Sandoval]

Hello There,

It seems like you are encountering a bandwidth limitation and maybe over-utilizing the USB bus network.  A good way to relieve some of the bandwidth usage is to reduce the amount of communication/transfers on the USB network.  With that said, can you use an internal hard drive instead of a USB external drive?  Try to specify the ASCII/LVM file in a local disk instead of an external disk.  Regarding acquisition, what are the sampling rates for the analog input channels?  Sampling at a considerably fast rate will cause your system to crash if the USB bus cannot handle offloading the information in time.  You can reduce bandwidth by reducing the sampling rate of your acquisition.  Note that the maximum transfer rate for USB 2.0 is about 480 MB/s and can fluctuate depending on various factors.   I would reference the following link below to further troubleshoot:

USB DAQ Bandwidth Considerations and Troubleshooting

http://zone.ni.com/devzone/cda/tut/p/id/9732

USB Specification

http://www.usb.org/developers/docs/

I hope this helps.

[OKors]

As Roman asked already, what are your sample rates?

I've logged over two weeks of data (temperature vs. load of a specimen in a thermal chamber) without problems. My sample rate was something like 2 sample per minute though (0.008333...Hz).

I guess I'm just reiterating the possiblity that it may be a bandwith limitation since my acquisition went much longer than 72 hrs without freezing.

Running XP pro on outdated Dell P4 desktop pc's.

You may also want to double check your external HDD settings. Some newer drives have power saving settings which will spin down the drive after a certain amount of inactivity. If it's going into standby perhaps there's a conflict with the software not being able to wake the drive up during a I/O request.

[Maksim]

I am sampling at 5 KHz per channel. I guess it comes out to about 20GBs of data per day.

I was able to record onto internal drives up to 80GBs. I have to get bigger internal drives to test out longer recordings.

I'm also using TXT file because LVM is only half the size f a TXT file but importing it into our needed analysis software is an enormous hassel.