Intervalometer

Abstract: A flow meter, or flow path intervalometer, transmits a transmission signal modulated with digital pseudo-noise or similar code. The received signal is correlated with the transmitted signal at successive times to produce a correlation function having a peak at a time to equal to the propagation time. The code is selected such that the side lobes of the correlation function are small. An interpolator determines a precise time of maximum correlation. In one embodiment, upstream and downstream correlation functions are defined and are correlated to determine an upstream-downstream propagation time difference interval Δt. In a preferred embodiment the digital code is a Barker code, and the transmitted signal is a finite interval wave which is phase modulated by the Barker code. In another embodiment, the received signal is a reflected signal which is range gated so as to represent flow data originating from a desired region within the conduit. The signal is sampled in phase quadrature and transformed to determine its frequency domain representation, and the devide derives local flow rate information from Doppler information. In yet another embodiment, a plurality of transducers are arranged to provide a number of sampling paths across the conduit, and the flow meter varies the range gating interval for the signal received along each path to derive a Doppler frequency, hence flow rate, for each of many sample intevals or bins along the path. The total flow in the conduit is then obtained by summing the flow in each bin times a cross-sectional area weighting factor.

Abstract: A new and improved method and apparatus are provided for non-invasive monitoring of changes in blood glucose concentration in a tissue specimen and particularly in an individual. The method uses acoustic velocity measurements for monitoring the effect of glucose concentration upon the density and adiabatic compressibility of the serum. In a preferred embodiment, the acoustic velocity measurements are made through the earlobe of a subject by means of an acoustic probe or monitor which includes a transducer for transmitting and receiving ultrasonic energy pulses to and from the blood flowing in the subject's earlobe and a reflector for facilitating reflection of the acoustic pulses from the blood. The probe is designed in such a way that when properly affixed to an ear, the transducer is positioned flush against the anterior portion of an earlobe while the reflector is positioned flush against the interior portion of the earlobe. A microthermocouple is provided on the probe for monitoring the internal temperature of the blood being sampled. An electrical system, essentially comprising a frequency generator, a time intervalometer and an oscilloscope, is linked to the glucose monitoring probe. The electrical system analyzes selected ones of the pulses reflected from the blood sample in order to determine therefrom the acoustic velocity of the blood which, in turn, provides a representation of the blood glucose concentration levels at the time of the acoustic velocity measurements.

Abstract: An improvement of the pulse‐echo‐overlap (PEO) method is proposed to make it accessible for computer control. The modification makes it possible to avoid the systematic and subjective errors of the original PEO method. A digital oscilloscope and a frequency synthesizer is controlled by a personal computer providing a fast automatic method for determination of ultrasonic wave transit times. Description of the method and the computer program, as well as the technical parameters is given. The Panametrics 5053A ultrasonic time intervalometer has been slightly modified to be applicable in the new configuration with a better precision. The 0.5 ppm precision velocity determination in water requires a 0.0003 °C level temperature control and reproducible wettability of the surface of the transducer. For both problems, a practical solution is proposed. Error analysis shows that the reproducibility of measurements is within 0.5 ppm.

Abstract: An intervalometer for determining the transit time of an ultrasonic energy pulse through a fluid medium employs an automatic gain control amplifier circuit for amplitude stabilizing the electrical signal derived at a receiving transducer. The automatic gain control circuit tracks both a rapidly increasing and a rapidly decreasing signal amplitude. In various embodiments, synchronous switching can be employed in conjunction with a single amplifier and a plurality of storage elements to rapidly scan a plurality of signal paths and for providing automatic gain control capability on each path. The intervalometer further has a "slipped cycle" capability for accurately determining arrival time when is is known that the signal pulse will be within a certain range of times. In addition, the relative time difference between two arriving signal pulses can be accurately determined using this method so long as the range of time difference is sufficiently small. The intervalometer also provides for bad data rejection based upon limits applied to either transit time or signal amplitude.