Why are the best standard resistors often kept immersed in an oil bath?

The best standard resistors are often kept immersed in an oil bath primarily to improve temperature control. Temperature stability is crucial in maintaining the accuracy of resistance measurements. Resistors can change their resistance value with temperature fluctuations; therefore, keeping them in a temperature-controlled environment helps minimize any variations that can arise from ambient temperature changes.

The oil bath provides a uniform temperature around the resistors, which helps in providing a stable thermal environment. This stability is essential for calibration processes and for ensuring precise measurements in various applications. Maintaining consistent temperature conditions reduces the thermal noise and enhances the reliability of resistance standards over time.

This approach is particularly important for high accuracy and precision in laboratory settings where slight differences in temperature can lead to significant errors in resistance measurements. By ensuring that the resistors remain at a stable temperature, the oil bath plays a critical role in achieving and maintaining low uncertainty in resistance values.