Fluke Calibration

Fluke 720A Kelvin-Varley Voltage Divider

The Fluke 720A Kelvin-Varley Voltage Divider generates 1100V and 11W of power. 720A models provide an absolute linearity of 0.1 ppm, a temperature coefficient of linearity of 0.1 ppm/°C and a self-calibrating capability. This product is a seven-dial primary ratio standard which meets the most exacting requirements of the standards laboratory, rendering the 720A superb accuracy in comparing primary and secondary voltage and resistance standards. 720A dividers feature two high input terminals. The terminal labeled INPUT 1.0 is for general use in all Kelvin-Varley applications for which direct reading, in ratio, is desired. The terminal labeled INPUT 1.1 is used for voltage measurement applications when both direct reading in voltage and over-ranging are desired. A demonstration of this application is the measurement of standard cell voltages; use of the 1.1 INPUT at a level of 1.1V in this application results in divider resolution of 0.1 microvolt, and allows comparison of standard cells to within 1 microvolt. The linearity has a small power derating coefficient of 0. 2 ppm per watt, which is achieved by matching the resistors' temperature coefficients close to zero. Only thoroughly aged resistors of the highest quality are used in 720A Kelvin-Varley Voltage Dividers, with linearity change per year not exceeding one part per million unless the instrument is subjected to abuse.