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发表于 2014-5-9 10:33
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来自 上海市浦东新区
要翻墙才能看的....我贴一段过来
MEASURING OUTPUT IMPEDANCE: As seen in the diagram above the output resistance forms a voltage divider. By measuring the output voltage with no load, and with a known load, you can calculate the output impedance. This online calculator makes it easy. The no load voltage is the “Input Voltage”, R2 is the known load resistance (don’t use headphones), the Output Voltage is the loaded voltage. Click Compute and R1 is the calculated output impedance. This can be done using a 60 hz sine wave file (Audacity can create such a file), a Digital Multi Meter (DMM), and a 15 – 33 ohm resistor. Most DMMs are only accurate around 60 hz. Play the 60 hz sine wave file and adjust the volume for about 0.5 volts. Then attach the resistor and note the new voltage. For example, 0.5 volts with no load, and 0.38 volts with a 33 ohm load gives an output impedance of about 10 ohms. The math is: Zout = (Rload * (Vnoload - Vload)) / Vload |
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