Apparatus for monitoring gas content on a site, to provide an indication if an undesirable gas content occurs, comprises a transmitter for feeding ultrasonic waves through the gas to a receiver. The ultrasonic waves are frequency-modulated and the phase of the modulation at the receiver relative to that at the transmitter is monitored. Either the relative phase is maintained constant, for example by a phase-locked loop so that the modulation frequency varies as a function of the gas content, or the frequency is maintained constant and the phase varies with the gas content. Any appreciable change in the frequency or phase may indicate a potentially undesirable change in the gas content. A plurality of transmitter/receiver pairs can be enabled in sequence to monitor a large area, the respective frequencies or phase displacements being monitored by a central processor.
A measuring ultrasonic wave transmitter comprises a negative immitance converter inserted between an ultrasonic transmitting transducer and a drive amplifier for driving the transmitting transducer. The output impedance of the drive amplifier, the damping impedance of the transmitting transducer and the impedance between the transmitting transducer and the drive amplifier are offset by the negative impedance caused by the negative immitance converter. A measuring ultrasonic wave receiver comprises a negative immitance converter inserted between a receiving transducer and a pre-amplifier for amplifying the output of the receiving transducer. The damping admittance of the receiving transducer and the load admittance of the receiving transducer are offset by the negative admittance caused by the negative immitance converter.
In a fire monitoring system for monitoring the occurrence of a fire in which a space to be monitored is imaginarily subdivided into plural subspaces so that plural channels passing through the subspaces are set so as to intersect to each other in a lattice form. The propagation speed of ultrasonic waves propagating through each of the channels is measured, on the basis of which the propagation speed of the ultrasonic waves in each of the subspaces is calculated in the same manner as the solution for each element of a matrix is obtained, and then the temperature in each of the subspaces is obtained. By providing the system with a humidity sensor, the temperature for a dry condition is obtained.
A steam quality monitor monitoring the quality of steam flowing in the pipe includes capacitance sensing apparatus which senses the capacitance of the flowing steam and provides a capacitance signal corresponding to the said capacitance. Another sensor which may be either a temperature sensor or a pressure sensor senses either the temperature or pressure of the steam and provides a representative type signal. Circuitry connected to the capacitance sensor and to the temperature or pressure sensor provides an output corresponding to the quality of steam in accordance with the capacitance and the temperature or pressure signal.
The present invention is a system for the detection of chemical vapors in the atmosphere based on detecting radiation from the molecules of the vapor. The radiation is induced by energy transmitted from the system at a frequency close to an absorption frequency of the molecules of the vapor to be detected. The system provides a easily used means for the excitation and detection of the vapor by virtue of the common tuning control of the system and the direct detection of radiation at the absorption frequency excited by the transmitted energy.
A fluid monitor for determining the percent composition of a fluid mixture of unknown composition when compared to a reference fluid mixture of known composition.
