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Do you need high-accuracy working standards for precise, on-site resistance calibrations? If you'd like to avoid maintaining traditional standard resistors in oil baths, Hart has a complete assortment of DC air resistors manufactured by Fluke, with Fluke's proprietary tellurium-copper five-way binding posts. The Fluke 742A Series covers values from 1 ohm all the way to 10 megohm. These are the finest-quality air resistors you can buy. They're durable, easy to maintain, and easy to use. Their excellent temperature stability allows them to be used from 18°C to 28°C with typically less than 2 ppm degradation. Using the calibration table supplied with the standards, which lists corrections in 0.5°C increments, this uncertainty can be reduced to near zero. Care has been taken to reduce resistance changes brought about by thermal and mechanical shock. Retrace (shift in resistance) is typically less than 2 ppm after cycling between 0°C and 40°C. Each of these resistors comes with a NVLAP-accredited report of calibration from Fluke. Accredited recalibrations are available from either Fluke or Hart.