How to take binary data from NI-4774 24bit

[bilik]

For fast data streaming to disk (for off-line analysis) I need to read binary data from NI4474. This board has 24-bit AD converter. In AIRead function in LabVIEW I'm able to read just I16 datatype. On NI-web page I found this:
-------------------------------
Problem: The binary datatype out of the AI Read VI is 16 bits. The bit resolution of the NI 4472 board is 24-bit, therefore a sample is 24 bits wide. When choosing a datatype such as binary, each sample in memory can only be 16 bits wide. If you try to store 24 bits of information (4472) in a 16-bit element, information is lost. The eight less significant bits of the number will be lost in this case.

Solution: An alternative solution is to use a 32-bit size datatype (
scaled data for the AI Read VI) to store the data from the NI 4472 and convert it to a 32-bit binary number after the acquisition.
-------------------------------
May somebody help me how to swithc to "a 32-bit size datatype (scaled data for the AI Read VI)". Or is there any way how to read from AIread DBL datatype. Do I lost some very small signals because of 24bit converted to SGL precision?

Thank you for any help.

[logman]

Traditional DAQ is limited to returning SGL or I16 binary data. A Single-Precision floating point number is 32 bit, but only 22 of the 32 bits are actually used for representing the numeric information, which means that it can represent data from a 447x board more accurately than a I16 number, but it still won't represent the full 24 bit accuracy of the board.

I would recommend programming the boards in DAQmx because it can stream data to disk more efficiently, and it supports using 32 bit integers for binary data. There is a shipping example in LabVIEW 7.x which demonstrates streaming binary data to file with DAQmx called Cont Acq&Graph Voltage-To File(Binary).vi. This example can be found in the example finder under Hardware Input and Output>>DAQmx>>
Analog Measurements>>Voltage.

Good Luck,
Logan Kunitz