Accessing Time in calling GPIB function of VISA

[kc1714]

We are using the Ni-488 to control HP Power supply. By calling the function hp663x1_setvolcur(xxx), the accessing time is around 2s. Could it be faster by using GPIB command directly ? OR bypass visa functions ?

the second question is whether GPIB has a faster accessing time or Ethernet in terms of controlling the equipment.

[Dan_Mondrik]

The time difference of making VISA calls vs NI-488 calls is negligible. If your function seems slower than what you think the device is capable of, perhaps you can use NI Spy to find the slow parts. Sometimes this will point out ways for you to make more efficient library calls.

As far as whether GPIB or Ethernet is faster, well, it depends on what you're doing. Obviously GPIB has a much lower first-byte latency. So for small transfers, GPIB is better. GPIB is also much more deterministic than Ethernet. But if you're transferring large multi-megabyte waveforms, then 100-Mb Ethernet may work better.

Dan Mondrik
Senior Software Engineer, NI-VISA
National Instruments