Development of a four-channel system for Johnson Noise Thermometry

Long integration time is necessary to reach low uncertainty when measuring temperature through Johnson Noise Thermometry (JNT). The main goal of the NIST JNT experiment is to achieve a 6×10^-6 relative uncertainty in the measurement of the water triple point, which could contribute to the re-determination of Boltzmann´s constant. A four-channel JNT system, which will reduce the measurement time two-fold, is being developed with new components, including a switchboard, an analog to digital converter (ADC) and a programmable, recharging power supply system. While implementing the new ADC, a source of systematic error was revealed, as well as a means to increase the measurement bandwidth.