At the heart of the Model 1281, two specially conditioned 10-volt zener references are continuously inter-compared to minimize drift rate. Coupled with the DC input amplifiers incredibly low 0.25 V/C temperature coefficient, this allows the Model 1281 to achieve a 10-volt range stability over a 1 year period and +/-5C temperature range of 3ppm. Thats as good as many Weston cells. And because the Model 1281s temperature coefficient is far superior to a Weston cells, you dont have to worry about precision temperature control.
Add the fact that it offers exceptional 0.1 ppm (+/- 2 V) single-range linearity from zero to 20 V, and you realise that the Model 1281 not only substitutes for Weston cells. It also doubles up as a highly sensitive null detector (with an input impedance >10 G) and a Kelvin Varley divider.
The Model 1281 also features exceptional AC performance, with 1-year uncertainties significantly below 100 ppm up to 10 kHz on its 1 V to 100 V ranges. Its spot calibrated frequency feature gives you even greater precision. Coupled with unique AC/DC transfer capabilities, this allows the Model 1281 to replace a conventional thermal transfer standard.
The Model 1281 also has unique Ohms measurement features. Its active Ohms Guard terminal lets you guard out leakage current paths when measuring very high value resistors. And its LoI mode prevent excessive self-heating in PRTs. The Model 1281s 2-input ratio function allows you to use it as a high performance automated bridge.