NI 5105 Onboard Memory

The NI 5105 allocates at least 256 bytes of onboard memory for each record in a single multirecord acquisition. Samples are stored in this buffer before transfer to the host computer. Thus the minimum size for a buffer in the onboard memory is approximately 128 12-bit samples. Software allows you to specify buffers of less than these minimum buffer sizes but only the specified number of points are transferred from onboard memory into the host computer memory.

The total number of samples that can be stored depends on the acquisition memory size option. The maximum number of records in a single multirecord acquisition is determined by the the size of the memory option divided by 256 bytes (128 samples), as shown in the following equation:

The memory options are 16 MB, 128 MB, or 512 MB, and the available memory is divided among all enabled channels.

Triggering and Memory Usage

During an acquisition, samples are stored in a circular buffer that is continually rewritten until a trigger is received. After the trigger is received, the NI 5105 continues to acquire posttrigger samples if you have specified a posttrigger sample count. The acquired samples are placed into onboard memory. The number of posttrigger or pretrigger samples is only limited by the amount of onboard memory.