NI-5105 Overrange detection implemenation using NI-SCOPE .NET Class Library

[gpbart]

Hi,

if I correctly understood the NI High-Speed Digitizers Help, there is no hardware over range detection mechanism on any High Speed Digitizer without OSP, e.g. the PXI NI-5105.

So I'm looking for some advises on how to implement such a function using the NI-SCOPE .NET Class Library.

Any help is welcome.

Thank you,

Guillaume
Application Engineer

[Raajit_Lall]

Hi,

The digitizers are calibrated to have a little bit of an extra buffer for a requested range.  If you set a range to +/-5V for example (10V) you can still measure about 5.1V without clipping.  However here are some options that you have.

1.  Unscaled Data:  You can fetch the unscaled data and this way you will be able to check to see if the signal is extending across the full range.  The data will be returned in 16 bits and the 5105 is a 12 bit device, so the lower 4 bits will be zeroed.  The range for such a case will be 0x8000 to 0x7FF0.  You can compare your measurements to these two values and if you are ever measuring either of these values then you can consider your signal to be over loading.

2. In scaled data you do not really have a method of finding out what you extra buffer is going to be.  You could however, just check the values in software, against the maximum and minimum that you asked for, it is not really going to be clipping at these values because of the extra buffer that I mentioned earlier, but this is still a safe way.

Hope that helps.

Regards,