4mm2 twin and earth cable

The accuracy of a tenths mic is very unlikely to be a "tenth" ebee, however good the operator. The electronic one above probably has an adjustment look-up table it uses to allow for calibration to get the accuracy to spec. Remember any wear or inaccuracy anywhere in the system makes the accuracy less, hopefully, the calibration lab gets it back to spec, mechanical mics go in the bin, although they are relatively cheap. The thread usually wears out first, this wrecks the linearity, errors are different on various parts of the range. My CNC lathe had electronic correction of the co-ordinate control system, the computer added or subtracted an error from the DRO scales to correct any errors, calibrating the whole lot took hours with Grade 1 slip gauges to 4 feet or so, each of the gauges had a correction of some amount of a few microns to add or subtract too, which had to be fed in manually. The lathe did superbly accurate work though so probably worth the effort (and cost!).

The accuracy of a tenths mic is very unlikely to be a "tenth" ebee, however good the operator. The electronic one above probably has an adjustment look-up table it uses to allow for calibration to get the accuracy to spec. Remember any wear or inaccuracy anywhere in the system makes the accuracy less, hopefully, the calibration lab gets it back to spec, mechanical mics go in the bin, although they are relatively cheap. The thread usually wears out first, this wrecks the linearity, errors are different on various parts of the range. My CNC lathe had electronic correction of the co-ordinate control system, the computer added or subtracted an error from the DRO scales to correct any errors, calibrating the whole lot took hours with Grade 1 slip gauges to 4 feet or so, each of the gauges had a correction of some amount of a few microns to add or subtract too, which had to be fed in manually. The lathe did superbly accurate work though so probably worth the effort (and cost!).