05-06-2010 01:39 PM
I have a USB-6212 DAQ device and it appears that it does NOT support input overload detection (exception is raised when I poll it) but I want to make sure it's not just a coding error.
Where would one find out if a DAQ device supports the input overload detection? The user manual is mute on this subject.
thanks
Bob
05-07-2010 03:46 PM - edited 05-07-2010 03:47 PM
Hi P15218,
If you search overload protection in the DAQmx Help you will find this:
DSA devices support overload detection in both the analog domain (pre-digitization) and digital domain (post-digitization). An analog overrange can occur independently from a digital overrange, and vice versa. For example, an IEPE accelerometer might have a resonant frequency that, when stimulated, can produce an overrange in the analog signal. However, because the delta-sigma technology of the ADC uses very sharp anti-aliasing filters, the overrange is not passed into the digitized signal. Conversely, a sharp transient on the analog side might not overrange, but the step response of the delta-sigma anti-aliasing filters might result in clipping in the digital data. Some DSA devices support both analog and digital overload detection, while others support only digital overload detection. Consult your device documentation for more information on the overload detection capabilities for your device. Two NI-DAQmx Read attributes/properties allow you to check for overloaded channels. The first is OverloadedChansExist. This attribute/property returns a Boolean true if one or more channels experience an overload condition. The second is OverloadedChans. This attribute/property returns an array of strings indicating which channels (if any) experienced an overload condition. You must query the OverloadedChansExist attribute/property before querying the OverloadedChans attribute/property. OverloadedChansExist reads the overload condition from the device and caches it in the driver. It also resets the overload condition of the device after it is read. Subsequent reads of OverloadedChans attribute/property will read the overloaded channel information cached in the driver from the previous OverloadedChansExist query.
Regards,