Is it possible to measure different types of biopotentials at the same time with the Octal Bio Amp?

Yes, the FE238 Octal Bio Amp (and the discontinued ML138) can be used to measure different biopotentials on a single subject (EEG, EOG, EMG and/or ECG). To measure biopotentials in two subjects, it is recommended to use separate amplifiers or the GT201, as this unit has two independent grounds.