The PDM35 was a follow-up to the earlier, highly successful, DM2 multimeter. It was launched in New York in 1977 and was aimed at the service and hobby markets. Its name was derived from its functionality - a personal digital multimeter with a 3.5 digit display.

The device looked more like a pocket calculator than a multimeter. This was no coincidence - Sinclair's designers re-used the case originally designed for the Sinclair Oxford calculator. Despite the somewhat crude looks of the PDM35, it was quite reliable, with a claimed accuracy of 1%.