Email Document Reference

Enter your email address below and the reference for this document will be sent to shortly from webmaster@ceesi.com.

Title: Low-Frequency Thermal Voltage Converter Calibrations At NIST
Author: Thomas E. Lipe
Source: 1995 Measurement Science Conference
Year Published: 1995
Abstract: It is well known that the performance of ordinary thermal voltage converters (TVCs), generally consisting of the thermoelement (TE) in combination with a current shunt or range resistor, begins to degrade at frequencies below audio frequency (20 to 30 Hz). this decrease in performance is due to the thermal time constant of the TE. At low frequencies, the TE does not thermally average the input rms waveform, and time-dependent variations of the output emf occur. The time constant of traditional vacuum-bulb TEs is on the order of a few seconds however, newer solid-state and thin-film TVCs may have time constants on the order of tens of milliseconds, with a corresponding increase in the frequency where thermal averaging begins. The work reported here is the culmination of a project to quantify the low-frequency behavior of both types of TVCs. It describes the NIST low-frequency ac-dc voltage standards and the build-up process for the NIST low-frequency calibration service from less than one volt to 100 volts. The new NIST uncertainty for low-frequency ac-dc voltage calibrations is reported and the statistical basis for the lower uncertainty presented.

In order to prevent spam and automated file downloads for documents within the Measurement Library, please follow the instructions below and then you will be able to email a reference to this article.