Noise evaluation circuits

This can further be enhanced by the so-called lock-in technique, in which modulated signals are used, which after demodulation separate the desired signal from the noise. Both techniques are described here by examples one is a monolithic pressure sensor with moderate piezoresistive bridge signals and the other is a signal evaluation circuit for a high-pressure sensor with very small sensor signal levels. 

The detector is protected from external noise by enclosing it within a grounded metallic box, and power is supplied via a local filter. Those circuits that are sensitive to electronic noise (mixers and preamplifiers) were isolated with the help of aluminum cases connected to the analog ground of the electronic assembly. The assembled selective microvoltmeter assembled detector was evaluated for its sensitivity, linearity, and pass bandwidth. This study was carried out with the help of a calibrated HF generator that was attached to a calibrated attenuator and so provided a sinusoidal voltage of amplitude 0.1-500 p,V and a frequency tunable between 0.5 and 8 MHz. 

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