| ??? 03/30/06 03:18 Read: times |
#113382 - Answers Responding to: ???'s previous message |
Suresh said:
So i couldnt get resonable info on why you have said that difference voltage as AC components of this modulation. The actual voltage drops are the result of two different currents, namely 12.5mA and 7.5mA, or by other words 10mA +-2.5mA. But what we get finally at the output of amplifiers is not the DC component, means 10mA, but only the AC component. means the +-2.5mA part. Or by other words, Ureed,ss and Ux,ss is just the amplitude of the square wave modulation, which contains the effect of the +-2.5mA part but not the DC component, means 10mA part. Suresh said:
So i think this would also give the VCR (Variable Contact Resistance).
To do this, can the successive readings be taken by 1)running a for loop in the software part or, 2) should the coil that drives the switch be subjected to some frequency for a short period? The contact of reed relay is closed during the whole measurement. Only the BC337 toggles. Before the reed relay is connected to the circuit, switch-off the BC337. Then, connect the reed relay to the circuit. Then, turn-on the reed relay, so that the reed contact is closed. Then, begin the modulation by toggling the BC337. Taking the average of succeeding readings is needed, because ultra small signals have to be ampflified, while the intrinsic noise of OPamps becomes relevant. Kai |
