Ni-Scope time per record

[ESD]

I am just starting with Labview so this may be an easy question.


I have a PXI-5105 digitizer and I would like to be able to set the time per record attribute.  However, when I try to do this with a property node I get the error message:

The channel or repeated capability name is not allowed.

Attribute: NISCOPE_ATTR_HORZ_TIME_PER_RECORD, Channel: 0

I can set the min. sample rate and min. record length to adjust the time per record, but I am confused about why you can only set minimum values of the parameters.  Why not set the absolute sample rate and record length giving an absolute time per record?  Are these parameters just adjusted to the next higher, and available value?

[JoeFriedchicken]

Hi ESD and welcome to the NI forums,

The property you're trying to use is part of the legacy driver support and is now considered obsolete [1]. It remains part of the driver, though, for legacy hardware, but a 5105 is new enough that it doesn't use this older API.

The recommended way to configure horizontal timing is using the other properties you mentioned: minimum sample rate and minimum record length. The reason that you cannot specify an exact rate or length is because the board's clock cannot be set to any arbitrary frequency and so it will be rounded up to the nearest valid setting [2].

However, if you still prefer to set record length according to time, then I suggest doing what you have been doing: specify a sample rate and record duration and then calculate the minimum record length.

Please let me know if you'd like further clarification.

[1] niScope_ConfigureAcquisition :: NI High-Speed Digitizers Help » Programming » Reference » NI-SCOPE Function Reference Help » Functions » IVI Compliance/Obsolete Functions
[2] Coercions of Horizontal Parameters :: NI High-Speed Digitizers Help » Programming » Getting Started with NI-SCOPE » Coercions

[ESD]

Thank you Joe.  That makes sense. It would be redundant to have parameters to set sample rate, # of samples per record, and time per record.