I've now got the DC ranges calibrated using the other 7081 as a yardstick. I've now moved on the the AC ranges and am having a problem calibrate,vac=0.1,high=0.100019 OK Calibration incomplete 0.100021 : : 0.100031 : : 0.100041 : : : 0.100302 and still climbing. The other meter is reading a rock steady 0.100019 Vrms Interestingly if I switch to the AC+DC volts range it reads a stable 0.099868V (a bit low). Thanks David Partridge