7055 and 7065, Solartron's new microprocessor controlled digital voltmeters, offer superlative measurement capability plus a choice of processing programs. System flexibility too, the interface options being carefully chosen to cater for the majority of existing or projected instrument interconnection systems. 7055 and 7065 carry out the same functions, but whereas 7065 has a maximum scale length of 6 x 9s (actually 1399999), that of 7055 is limited to 5 x 9s. To simplify the use of this Manual the description will be that for the 7065 (6 x 9s); 7055 (5 x 9s) will be mentioned only in instances where it is not identical. As basic voltmeters both measure: dc voltage: the result being the average value of the input during a selected period, ac voltage: the instrument senses the mean value of the ac content of the input and displays the rms equivalent assuming a sine wave, resistance: the result being the average value of the unknown during a selected period. Ranges can be selected individually or automatically, there is a choice of scale length and digital filtering can be applied. Readings can be taken singly or a succession of readings may be made. More powerful versions of these two voltmeters, in addition to measuring the unknown inputs, process those measurements to give other useful results. Typical processes are: maximum or minimum of a string of measurements, comparison with preset limits. Whether the instrument supplied is the basic voltmeter or is the processing version, both carry the identical front panel controls and captions which apply to the full processing voltmeter. This permits a user to change a simple voltmeter into the processing version by adding an internal module. Finally, both the basic instrument and the processing version can be fitted with a system interface. This enables the voltmeter to be controlled by coded electrical commands, and to output data which are the results of simple measurements or of processed measurements.