Abstract: In this study, a biological signal acquisition and processing set has been designed and realized. The set can be used in teaching basic principles in recording and analizing of biological signals. This set can be used in biomedical electronics engineering and biomedical technology laboratories. The set is especially helpful to teach how the biological signals are acquired and processed. ECG and EMG signals can be selected, amplified, filtered and transferred to the monitoring devices with this set while patient safety is provided. There are a number of connection points in the set for observing the signals at various levels. Students can make measurements at each of these steps with the connection probes outside the set. The output signals can be observed using an oscillascope. They can also be observed from a PC monitor with an electronic card connected to ISA bus. Keywords - Biopotantial, Instrumentation, Experiment Set 1. Sources and Types of Biological Signals: The basic building blocks of human body are cells. When electrodes are placed inside and outside a cell without affecting physiology of the cell, a voltage between –50 and –100 mV is measured. This voltage is called “Membrane Potential”. Source of this membrane voltage is the difference between the concentrations of K + , Na + ve Cl - ions inside and outside the semi-permeable membrane. As stated by Goldman, the membrane potential while the cell is at rest can be calculated by the formula[ 1 ], [ ] [ ] [ ] [ ] [ ] [ ]         + + + + − = − + + − + + i CI O NA O K O CI i Na i K m CI P Na P K P CI P Na P K P q kT V ln [ 1 ] Vm , in this formula, represents the potential difference between inside and outside the cell, in mV. [CC] i is the concentration of the ion CC inside the cell in mmol/litre. [CC]o is the concentration of the ion CC outside the cell in mmol/litre. P CC : Membrane permeability for CC ion cm/s k : Bolttzmann constant, 1.38 10 -23 J/K T : absolute temperature in K q : electric charge of a proton, 1.602 10 -19 C Biopotentials are electrical potentials that appear with the currents that occur with the flow of ions inside a biological structure. The flow occurs with the activation of the excitable cells in nerve, muscle and seceration gland. These excitable cells can generate and propagate action potentials when they are excited with electrical stimulation of the membrane, chemical effects that change permeability of Na, heat effects or mechanical effects. The potential inside the cell is more negative at rest. However, when the cell is excited, Na permeability of the membrane increases quickly for a short period of time. The negative polarity disappear for a while. The potential inside the cell becomes even positive. This is called depolarization. Return of the cell to its stable state is called repolarization. Graph of an action potential is shown in Figure-1. Figure 1:Action potential[4] time(ms) 100 80 60 40 20 0 -20 -40 -60 -80 -100 Vm (mV) 1 3 4 2 BIOPOTANTIAL INSTRUMENTATION SET Metin YILDIZ 1 , F.Nihal GULER 2 , Ahmet TURKMEN 3 , Derya YILMAZ 1 1 Vocational School of Biomedical Technology , Baskent University, Ankaral, Turkey 2 Gazi University, Technical Education Faculty, Teknikokullar ,Ankara, Turkey 3 Baskent University, Engineering Faculty,Biomedical Eng. Dep. Ankara, Turkey