Signal processing apparatus for ultrasonic thermometers

Abstract

Improvements in electronic apparatus connected with operation of ultrasonic thermometers consisting of an initiating electrical pulse generator which permits selection of the repetition rate at which the ultrasonic thermometer is to be operated, and, to avoid electrical interference caused by power switching, selective commencement of the initiating electrical pulse relative to the power line. Electronic amplifying and transmitting circuitry receiving the reflected information signal pulses from the ultrasonic thermometer amplify the pulses for transmission to pulse processing circuits remotely located from the furnace, assuring that sufficient signal amplitude is received by means of a returned automatic gain control signal to the amplifying and transmitting circuitry. The pulse processing circuitry utilizes a zero cross detector to ascertain the presence of reflected information signal pulses and separates low level noise from the reflected information signals in a peak detector circuit to present individual pulses for each initiating pulse and each reflected pulse from each discontinuity in the temperature sensing rod of the ultrasonic thermometer. Such is accomplished in a way as to minimize errors which can be caused by power line voltage variations, power line failures, and ambient temperature changes and in such a way as to minimize the complexity and cost of the circuitry. To ascertain that unwanted reflections are eliminated, a sync pulse processor generates a time window to block out all reflected pulses outside the time window of the information pulses of interest. The information pulses of interest are further processed to a plurality of counters which display the time between adjacent reflected signals received from adjacent discontinuities in the temperature sensing rod from which, by using known charts, can be ascertained the temperature of the temperature sensing rod between adjacent discontinuities.