I'm using a NI PXI-4070 to measure a signal of 10KHz square waveform with 5V amplitude(from keysight 33500B waveform generator). I programmed with Visual C and just modified from the NI example. I set the minimum frequency as 999Hz so that the aperture time was 2000/999=2.2ms, but it took more than 500ms to read the frequcny. I also set the same parameter in NI-DMM soft front panel, the measure result updated very quick(at least less than 500ms). I test both the function niDmm_Read and niDmm_Initiate/niDmm_Fetch, both of them took more than 500ms.
Can somebody help to check where I'm wrong? thanks.
An application called I/O Trace should have been installed along NI-DMM in your system. It will trace all calls made to the NI-DMM (and other) APIs. A good tip is to use this to see how the Soft Front Panel configures the device as you use it.
Also, you should check out InstrumentStudio if you haven't yet, a modern replacement for the NI-DMM Soft Front Panel.
Marcos Kirsch Chief Software Engineer NI Driver Software