20. IMPEDANCE MEASUREMENT20.1 THEORYImpedance is the frequency dependent resistance of alternative currents. It consists of the valueZ in and the phase = . The measurement displays both values above the frequency range.The phase displays the values of reactive and active resistance which together result in thevalue Z. = 0 consists of resistance only and = 90 consists of reactive resistance(reactance) only.The impedance measurement is needed when developing and testing loudspeakers. It is a valuefor the demand on amplifiers from loudspeakers. Smaller Z values demand powerful amplifiers.The phase reveals possible instability in amplifiers, which can create oscillation and damageloudspeakers. The phase angle should not be > + 60 .The impedance measurement enables the testing of electronic devices, resistors, capacitors andspools.20.2 ARRANGEMENTThe speaker is to connect to the speaker out socket.The selector is switched to IMP. The volume is disabled.The picture do not show the rightfunction positions. It is IMP20.3 MEASURINGThe impedance measurement uses the same graphics as used when amplitude frequencyresponse is measured.The measurement range reaches from 20Hz -20kHz. The right-hand axis displays the value Z.The range is from 0 – 50 .The change over between amplitude and phase measurements is initiated with the button58
