1. A device herein called picafina, having a proximal extremity and a distal extremity, to measure electrical activity, or signal, occurring in body cells, said device having a plurality of measuring electrode tips on the surface of said device, generally at or near the distal extremity of said device, and a signal carrying wire running inside and along said device, from the distal extremity of said device, where there are means to connect said signal carrying wire to said measuring electrode tips generally near the distal extremity of said device, to the proximal extremity of said device, where there are means to connect said signal carrying wire to other wires outside said device for connection to measuring instruments, said signal carrying wire having the purpose of carrying said signal measured by one of said electrode tips near the distal extremity of said device, to said proximal extremity of said device, from where said signal wire can be connected by said means to an appropriate measuring or recording instrument, for measurement or recording the value of said electrical activity or signal, and means to select one of said measuring tips and connect said selected measuring tip to said single wire to carry said electric signal from said electrode tip to the proximal end of said device, whereby it is possible to measure the voltage values at cells next to said measuring electrode tip inserted inside the body.