Stability evaluation of high precision multifunction instruments for traceability transfer

In the traceability transfer process from the national standards of the Istituto Elettrotecnico Nazionale "Galileo Ferraris" (IEN) to standards of calibration laboratories accredited by Servizio di Taratura in Italia (SIT), the use of high precision multifunction instruments, in particular of the digital multimeter, as reference standards turned out to be a good transfer method. In fact it combined the speed and cheapness of transfer to the uncertainty level of the process comparable to that obtained using high precision individual standards, such as 10 V DC voltage standards, standards resistors, AC/DC transfer standards and so on. In the present paper the authors describe how this transfer process is performed and what are the results obtained.