Audio Precision音频分析仪测试介绍[共23页]

1、AP Introduction meanwhile the other channel is set for zero volts. The measured channel left open. - Whatever signal is induced into the tested channel is measured at its output with an rms voltmeter and noted. A ratio is formed by dividing the unwanted signal by the above-noted output test value, a

2、nd the answer expressed in dB,AP introduction,Harmonic Distortion Concepts - Harmonic distortion may be measured and expressed as total harmonic distortion (THD), or as total harmonic distortion plus noise (THD + N). - THD is the distortion that occurs on harmonics of the original signal. Noise is t

3、he more random, uncorrelated distortion. - In all cases, stimulus from a very pure sinewave generator is fed to the input of device under test. The generator must have significantly lower distortions than that of device,AP introduction,Harmonic Distortion Concepts - THD refers to measurement methods

4、 which individually measure the amplitude of each significant harmonic in a narrow bandwidth, then combines them in root-mean-square fashion to produce a single number. - THD + N, refers to the measurement technique in which the fundamental component is removed by a bandreject (norch) filter and all

5、 remaining energy measured, including harmonics and noise,AP introduction,Harmonic Distortion Concepts - Bandwidth and THD+N The measured THD+N of a device will vary with the measurement bandwidth. You will almost always want to restrict the measurement bandwidth using high-pass and low-pass filters

6、, and you must include the bandwidth used when you state the result. THD+N is typically measured and reported in a 20 Hz20 kHz bandwidth,AP introduction,Harmonic Distortion Concepts - Level and THD+N The measured THD+N of a device will also vary with level and the frequency of the applied signal. Au

7、dio THD+N is typically measured and reported at a mid-range frequency (1 kHz or so) at the either the devices nominal operating level or at its maximum output level (MOL). - A THD+N versus frequency sweep or a THD+N versus amplitude sweeps will show how a DUT performs under varying stimulus,THD + N,Headphone output,THD + N,THD + N vs Level,THD + N,THD + N vs Le