Abstract: The signals to be measured are transformed in the system to discrete time digital signals by synchronous sampling. These digital signals are then processed by a digital signal processor for vector detection and for computing digital feedback sent to the sampling gates. The analyzer has improved characteristics in the area of linearity, drift and test port signal injection because of its highly optimized architecture based on synchronous sampling with digital feedback. It possesses unique characteristics such as the ability to tune to a harmonic or a subharmonic of the excitation frequency and a good sensitivity in a high impedance environment.

Abstract: The disclosure relates to a system for the detection of human presence in hazardous situations near moving machinery; appropriately shaped electrodes are placed in an area to be safeguarded and a radio-frequency signal of appropriate frequency and voltage is applied on the electrodes creating an alternating electric field around them. A bridge circuit is used to measure the capacitive impedance created by the electrodes and a dissipation factor is calculated from the real and imaginary parts of the impedance. If a foreign object is introduced into the electric field, the characteristics of the dielectric are modified creating a change of the value of the dissipation factor. The dissipation of energy in the high frequency region is much greater if this foreign object is a biological tissue as compared to other types of materials, such as conductors or insulators.

Abstract: The unknown capacitor or a standard capacitor are switched, one at a time, in parallel to a frequency setting circuit which sets the frequency of operation. The parallel combination of the unknown capacitor and the frequency setting circuit form a first parallel resonant circuit and the parallel combination of the standard capacitor and the frequency setting circuit form a second resonant parallel circuit. These resonant circuits are part of the feedback network of an oscillator. The bottom ends of the resonant circuits are connected to an instrumentation amplifier for maintaining the bottom ends at vertual ground in order to make three terminal measurements. A frequency meter is provided for measuring the frequency of resonance of the first resonant circuit and the second resonant circuit.