and not a measuring device, although it can be calibrated. A calibrated electrometer with a more robust aluminium indicator was invented by Ferdinand Braun and first described in 1887. According to Braun, the standard gold-leaf electrometer is good up to about 800 V with a resolution of 0.1 V using an ocular micrometer. For larger voltages up to 4-6 kV Braun's instrument can achieve a resolution of 10 V.

The instrument was developed in the 18th century