Yes Hitesh - you're right - there's no reason why I shouldn't keep the unit open all the time. For some inexplicable reason I thought that if one left a procedure after invoking UsbDrDaqOpenUnit(handle) from within it the unit would not like it unless the unit was closed before leaving. But that was...

Thanks Hitesh, sorry for the delay in replying, but as these crashes occur up to 24hrs after the program starts I need to wait. I replaced "Call " by "status= " and also I've tried two versions of usbdrdaq.dll (version 1.0.1.1 10 July 2014 and version 1.0.5.4 8 June 2015) but Excel still crashes wit...

I'm using DrDAQ with Excel 2000 VBA on a Windows 7 computer. I'm measuring the voltage at the scope input every two seconds, continuously. This voltage is normally zero. That's all the program does except when the voltage is >2V, which might occur every few days, then other things happen. This works...