Automation and Evaluation of Two Different Techniques to Calibrate Precision Calibrators for Low Frequency Voltage Using
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ORIGINAL PAPER
Automation and Evaluation of Two Different Techniques to Calibrate Precision Calibrators for Low Frequency Voltage Using Thermal Devices B. Pal, S. Ahmad* and A. K. Govil CSIR-National Physical Laboratory, New Delhi, India Received: 22 October 2010 / Accepted: 03 December 2012 / Published online: 11 January 2013 Ó Metrology Society of India 2013
Abstract: Low frequency (LF) voltage and current are important parameters in electrical metrology. The standards for LF voltage and current are established by assigning AC–DC transfer difference to thermal devices, i.e. thermal converters or thermal transfer standard along with current shunts. Automated calibration systems have been developed based on Null method and measurement technique developed by Budovsky for calibration of precision calibrator in LF voltage and current against thermal devices. The technique based on the Algorithm developed by Dr. Ilya Budovsky (National Metrology Institute (NMI), Australia) has been compared with the conventional null technique. Indigenously developed software has been used to calibrate the precision calibrator in the entire LF voltage and current range using Holt thermal converters and current shunts. Calibration results at 1 V, 10 V in the frequency range from 10 Hz to 1 MHz as well as calibration results of 1 A in the frequency range from 40 Hz to 10 kHz are presented in this paper. These result shows that the measurement technique developed by Budovsky has reduced the complexity of AC–DC transfer measurements, measurement time and the uncertainty in measurement. Keywords:
AC-DC transfer difference; AC voltage calibration; AC calibrator; Automated calibration
1. Introduction This paper explains how to use the null method and measurement technique developed by Budovsky [1] for calibrating AC calibrator using thermal devices. Both established techniques for the calibration of precision AC calibrator using thermal devices have been evaluated and compared. This paper also describes the automation of these two techniques which simplify the measurement process and their evaluation in terms of measurement uncertainty. The software platform used for its development is Agilent’s VEE Pro (Visual Engineering Environment Programming) a graphical user interface (GUI) [2]. The measurement setup for both the techniques and measurement results at 1 V, 10 V and 1 A have also been discussed. As AC–DC transfer measurements require large amount of data acquisition from the electronic equipments at various frequencies and voltage/current levels, therefore automation is almost today’s necessity. The automation software developed for these techniques can produce
*Corresponding author, E-mail: [email protected]
calibration report along with uncertainty budgets at each current/voltage point of measurement. 2. Software VEE Pro is a graphical programming environment optimized for use with electronic instruments that provides the fastest path to measurement analysis and helps in shortening the development time. It has hundreds of powerf
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