Abstract:
This investigation was prompted by a chance observation during trials of the ToMPAW
arm system [1]. The arm has a carbon fibre structure which, although not directly connected
to the system electronics, can act as an antenna for electromagnetic interference. The user
suspected that better control was obtained when the structure was grounded by touching it. A
more permanent solution was tried by adding a conductive plastic patch to the inside of the
socket, providing a safe high resistance ground path without discomfort (Figure 1). The user
reported a subjective improvement with this modification. Myoelectrode amplifiers are
designed with a high common mode rejection ratio (CMRR) and good d.c. isolation, and
externally applied signals would be expected to have little influence, so further investigation
was warranted.
