Power Analyzer Accuracy and Basic Uncertainty Calculator

1. Importance of Accuracy: In power measurement, understanding accuracy is essential for obtaining reliable measurements. Accuracy reflects the proximity of a measurement to the true value, which is the accepted standard. The difference between the measured and true values constitutes the error.

2. Understanding Systematic Measurement Errors

• Gross Errors: Typically due to user mistakes, such as incorrect instrument settings.
• Measurement Errors: Arise from the instrument or measurement system itself, including measurement probes and current transformers, internal losses, and calibration related errors.

3. Quantifying Accuracy

• Relative Error: Expressed as a percentage relative to the measured value or the instrument's full-scale range.
• Absolute Error: Denotes the direct difference between the measured and true values, often expressed with a plus-minus range.

4. Factors Influencing Systematic Measurement Errors:

• Measurement Reading: The expected measurement value obtained from the instrument.
• Measurement Range: The voltage and current input ranges of the instrument as configured for the application.
• Frequency: The fundamental frequency of the voltage and current signals.
• Power Factor: The ratio of real power to apparent power.
• Proper Configuration: Ensure the instrument is correctly set up for the specific measurement task, including selecting the appropriate range and filters.
• Regular Calibration: Periodic calibration of the power analyzer is vital to maintain measurement accuracy over time.
• Understanding Specifications: Carefully review the instrument's accuracy specifications, noting the conditions under which they apply. Uncertainty calculators can assist in converting relative error and measurement settings to worst case absolute error (guaranteed absolute accuracy).

5. Steps to Use the Uncertainty Calculator:

1. Download the Calculator and open the appropriate sheet for the instrument you’re using.
2. Input Data into the yellow-highlighted fields:

• Voltage and current readings
• Voltage and current measurement ranges
• Frequency
• Power factor

The calculator will automatically display the corresponding uncertainty values.

Learn more about how range affects accuracy here.