NI PXIe-4113 Measurement Configuration and Timing

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Edition Date: January 2018

Part Number: 370736U-01

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The NI PXIe-4113 can acquire measurements automatically after a sourcing operation or when triggered. The NI PXIe-4113 uses a successive approximation (SAR) ADC for sampling voltage and current.

The state sequence of the device measurement circuitry differs depending on the measure record length that you use. The measure record length indicates how many measurements to acquire after the measure trigger and before the measure complete event.

Multiple Asynchronous Measurement Timing

If you make multiple measurements that are each timed with asynchronous measurement start triggers, the measure record length is one and the NI PXIe-4113 measurement circuitry operates in one of the three active states:

  • Aperture time—During the aperture time, the NI PXIe-4113 samples the input signal and converts the signal two or more times at a fixed sample clock interval for the programmed aperture time of the device. The NI PXIe-4113 then averages these samples to generate the returned measurement.
  • Measure complete event delay—During the measure complete event delay, the measurement circuitry of the device waits for a length of time that you specify before generating the measure complete event. The default value is zero.
  • Asynchronous delay—During the asynchronous delay, the measurement circuitry of the device is idle until a trigger initiates the next measurement.

The following figure illustrates the sequence of these states for two sample measurements.

In this example, two measurements are made, so the measure trigger and measure complete event occur twice, once for each measurement. The aperture time is five divided by the sample clock rate, meaning that for each measurement, a total of six samples are averaged. The sample clock period is fixed for the device at a value of 1/10.5 kHz.

Measure Record Timing

If you make a sequence of hardware-timed measurements in response to a single measurement start trigger, you can configure the measure record length to greater than one and the NI PXIe-4113 measurement circuitry operates in one of the three active states:

  • Aperture time—During the aperture time, the NI PXIe-4113 samples the input signal two or more times and converts the signal at a fixed sample clock interval for the programmed aperture time of the device. The NI PXIe-4113 then averages these samples to generate the returned measurement.
  • Measure re-arm—During the measure re-arm time, which has a duration of one sample clock period, the measurement circuitry of the device waits before acquiring samples for the next measurement.
  • Measure complete event delay—During the measure complete event delay, the measurement circuitry of the device waits for a length of time that you specify before generating the measure complete event. The default value is zero.

The following figure illustrates the sequence of these states for a measurement record length of three.

In this example, the aperture time is five divided by the sample clock rate, meaning that for each measurement, a total of six samples are averaged. The sample clock period is fixed for the device at a value of 1/10.5 kHz. The measure record dt is the aperture time and the measure re-arm time added together.

Configurable Measurement Options

You can configure measurement options such as aperture time on the NI PXIe-4113 to achieve a desired accuracy and/or speed. Expand this book for information about how to configure measurements to achieve specific results.

Related Topics

NI PXIe-4113 Aperture Time

NI PXIe-4113 Triggers and Events

Measuring

Using the Device

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