You can create your own custom instruments using the LabVIEW graphical development environment. Instruments that you create using LabVIEW can take advantage of the full functionality of the LabVIEW development system, including data acquisition, instrument control, mathematical analysis, and so on.

For example, you can create the following kinds of instruments:

  • An instrument that acquires data from the real world using a National Instruments data acquisition device or modular instrument. Multisim will then use that data as a signal source for circuit simulation.
  • An instrument that displays simulation data simultaneously with multiple measurements (running average and power spectrum, for example) made from that simulation data.

LabVIEW instruments can be either input instruments, output instruments, or input/output instruments. Input instruments receive simulation data for display or processing. Output instruments generate data to use as a signal source in simulation. Input/output instruments both receive and generate simulation data.

All LabVIEW instrument types perform their functions continuously during simulation. For example, input instruments continuously receive simulation data from Multisim during simulation. Output instruments continuously generate simulation data during simulation. Input/output instruments continuously receive and generate simulation data during simulation.

Input instruments allow the user or creator of the instrument to set a sampling rate. This sampling rate is the rate at which the instrument receives data from Multisim. This sampling rate is analogous to the sampling rate you would set for a physical data acquisition device or modular instrument that acquires data from the real world. You should observe the Nyquist sampling theorem when choosing a sampling rate for your instrument. Note that the higher the sampling rate, the slower simulation will run.

  If the sampling rate is set to zero for a LabVIEW input instrument, Multisim chooses its own sampling rate based on the simulation timestep near the start of simulation.

Input instruments also allow the user or creator of the instrument to set an interpolation method. The interpolation method is the particular algorithm Multisim uses to transform unevenly-sampled SPICE simulation data into evenly-sampled LabVIEW Waveform Data Type data. The available interpolation methods are Coerce, Linear, Spline, and Force Step. Force Step is not strictly an interpolation method in that it forces the Multisim SPICE simulator to take additional timesteps that line up with the requested sampling rate.

If the particular LabVIEW instrument allows you to set the sampling rate and/or interpolation method, Multisim will recognize changes to these values during simulation.