Sinclair Radionics, 1977
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%.