NI 5160/5162 Onboard Memory

The NI 5160/5162 allocates at least 512 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 256 16-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 equal to the size of the memory option divided by 256 samples. Refer to the hardware specifications document for information about the memory options available for each device.

Triggering and Memory Usage

During an acquisition, samples are stored in a circular buffer that is continually rewritten until a trigger is received. These samples are known as the "pre-reference trigger" samples. After the trigger is received, the NI 5160/5162 continues to acquire post-reference trigger samples. The relationship of the number of pre-reference trigger samples to post-reference trigger samples is specified by the "Reference position" attribute (by default, 50% of the record length is post-trigger.) The acquired samples are placed into onboard memory. The number of pre-reference trigger or post-reference trigger samples is only limited by the amount of onboard memory.