| ??? 12/27/06 02:31 Read: times |
#130161 - Phase, capacitive load Responding to: ???'s previous message |
Alireza said:
Those diff amps introduce some error in phase relative to real voltage waveform that the load senses and also current waveform. We thought to use the same arrangement and type of diff amp both for reading voltage and current with the hope that these errors cancel each other. Not sure, what you mean. But, if it's a systematic error like the phase shift of an additional low pass filter, then you can take it into calculation, or try to cancel it by your methode. Alireza said:
And a new problem has been raised by one of my colleagues to keep us worry. What if the load itself has some significant capacitance for example 100nF, then the stability problem will become even more complex. What stability problem? With the methode I recommended the excitation voltage is provided by a sine oscillator offering a stable amplitude. That's all. The series resistance (shunt) is enough to decouple the output from capacitive loads and to guarantee stability. Also, as Steve already mentioned, 100nF looks rather unrealistic... Kai |
