What is the typical uncertainty for reference standards for DC voltage that can be purchased?

The typical uncertainty for reference standards for DC voltage is often specified by their precision and accuracy in measurements, particularly at a nominal value such as 10 V. The reference standards aim to provide reliable voltage outputs for calibration purposes, which helps ensure that voltage measurements in different equipment are consistent and accurate.

In this context, an uncertainty of 20 microvolts at 10 V indicates a high degree of precision, which aligns well with industry standards for quality in calibration. This level of uncertainty suggests that the reference standards can maintain accuracy within a very tight tolerance, making them suitable for various applications, including laboratory measurements and instrument calibration.

Other options present uncertainty levels that might be too low or high for typical purchased reference standards. For instance, an uncertainty of 50 microvolts may exceed the reliability required for many calibration scenarios. In contrast, an uncertainty of 10 microvolts or 5 microvolts could be more precise than what is commonly available in standard reference equipment for DC voltage. Therefore, stating 20 microvolts at 10 V provides a practical balance between accuracy and what is readily achievable in calibration standards purchased in the field.