Sourcing and Measuring Terminology

Refer to the following terms when learning more about the features and usage of the PXIe-4112:

  • Aperture Time—The period during which an ADC reads the voltage or current on a power supply or SMU. Aperture time can be specified in seconds (s) or power line cycles (PLCs). Measurement resolution, measurement speed, and frequency rejection are all functions of aperture time.
    Tip Select longer aperture times to improve measurement resolution; select shorter aperture times to increase the measurement speed.
  • Compliance—For power supplies and SMUs, a channel is operating in compliance when it cannot reach the requested output level because the programmed limit has been reached.
  • Line Regulation—A measure of the ability of the power supply or SMU to maintain the output level given changes in the input line voltage. Line regulation is expressed as percent of change in the output level relative to the change in the input line voltage.

    For NI DC power supplies and SMUs, the line regulation specification only applies to devices with an auxiliary power input.

  • Load Regulation—A measure of the ability of an output channel to remain constant given changes in the load. Load regulation expression depends on the control mode enabled on the output channel.
  • Resolution—The smallest change in the voltage or current measurement that can be detected by hardware. It is usually specified in absolute units, like μV or nA.
    • Measurement resolution is typically limited by the ADC used for the measurement, but may also be limited by other factors, such as noise.
    • Output resolution is typically limited by the finite number of steps that are available in the device DAC circuit, but may also be limited by other factors, such as noise.

    Refer to the PXIe-4112 Specifications for measurement resolution and output resolution information.

  • Sensitivity—Sensitivity is the smallest unit of a given parameter that can be meaningfully detected with an instrument under specified conditions. This unit is generally equal to the measurement resolution in the smallest range of a power supply or SMU.
  • Settling Time—Settling time specifies the time required for an output channel to stabilize to within a specified percentage of its final value. This value is typically included in the device specifications.