Quote:
Originally Posted by FrancoItaly
In my opinion, the quartz oscillator signal is already very stable and therefore no automatic amplitude control is required. The phenomenon simply causes an increase in signal output and it is not possible to obtain discrimination by observing only variations in amplitude, even in metal detectors, it is also important to consider the variations in phase amplitude as well as the variations in amplitude.
|
You haven't understood me FrancoItaly.
Not quartz oscillator amplitude control, but mixing amplitide control, which going from oscillator via several small serial capacitors 1pF to the base of tr2 bc183c. This place is main phenomenon detector.
Amount of oscillator signal is enough to suppress phenomenon signals which are bipolar in nature. In once case we have rising and in the other decaying control signal at the dc output of the sensor stage. In simple words mixing both signals - from the oscillator and phenomenon must be dynamically or variabile in accordance with some threshold of dc output amplitude.
We dont need suppression of phenomenon signal via constant amount of oscillator signal, nor undetected phenomenon signal. Mixing amplitude should be additive in some variabile values, small variabile offset, to maintain constant dc offset in some useful range for example from 3.05v - 3,75v at the output of sensor stage. We dont need overshooting or undershooting control dc volatge which is phenomenon amplitude modulated.
Best regards
dubulumach