I think its fuzzy but most all good DMM have it specified using some term. Its a term I see HP or Agilent use mostly. Fluke 5808a uses the term 'Transfer Uncertainty', which is inline with metrology replacing the term 'accuracy' with 'uncertainty' _and_ a confidence interval [ which was undefined by the term 'accuracy']. A common understanding of 'transfer accuracy' presumes it could be used as a transfer reference in a pinch. Transfer references in general are secondary references used to transfer the primary reference value to other devices; a Fluke 732b is a transfer reference, its portable and has defined accuracy to 30 days, while the primary reference, say a Josephson Junction, cannot be moved from its location. Per manual, the 3458a 'transfer accuracy' are specified for 10 minutes to a primary reference and requires the original calibration temperature +/- specified limits [ this is vital to control for ppm drift/temp]. For 10V scale, 10 minute accuracy is 0.05ppm, its 24h spec: 0.5 ppm + 0.05 ppm of scale. The other quoted accuracy is the 1 hr accuracy of 0.1ppm. As Dr. Frank points out very well the great value of this spec is making ratio measurements. However, its not implied by the stated manual specification. OTAH 10 minutes or even 1hr is barely enough time to run from the primary standard to your lab, so it must be used in other ways. Ratio measurements are independent of DMM drift since calibration: its most dependent on the shortest term accuracy, aka 'transfer accuracy', ambient temperature, linearity of the device and naturally, the accuracy of your reference. Based on the manual specs, the longer you delay making the ratio measurement the more likely the 3458a will drift, so keeping it under 10 min give you the best results; beyond it you're then at the 1 hour accuracy, and beyond 1 hr, you'd use the 24 hr accuracy. At 12:44 PM 5/4/2014, Jan Fredriksson wrote: >Is there a common understanding about what "transfer accuracy" means or is >it more of a fuzzy term? >_______________________________________________ >volt-nuts mailing list -- volt-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts >and follow the instructions there.