Acoustic method for measuring a signal propagation time in a medical liquid and device for using this method
First Claim
1. A method of measuring a signal transit time in a medical liquid required by a signal to pass through a measurement zone from an ultrasonic transmitter (2) to an ultrasonic receiver (3), in which a line carrying the medical liquid is arranged in the measurement zone, comprisingemitting a step-like signal (10) with the ultrasonic transmitter (2) such that the step-like signal (10) passes through the measurement zone, resulting in an oscillation-like received signal (12) oscillating about a resting level (11) on the ultrasonic receiver (3), the received signal being sampled at regular intervals Δ
- t and detected,checking the oscillator-like received signal (12) on the basis of a selection criterion at least during a half-period (14, 15) to determine whether the oscillator-like received signal (12) is the received signal produced by the step-like signal (10), andwhen the result of this check is positive, determining the signal transit time or the change in the signal transit time with an interpolated or extrapolated contact point (20, 21) of the oscillator-like received signal (12) with the resting level (11) in a received signal-time diagram.
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Abstract
This invention relates to the field of signal transit time sensors, in particular sensors based on ultrasonic transit times. Existing electronic control circuits for such transit time sensors for measurements on medical liquids, in particular blood, are extremely complex or their time resolution is limited. However, the present invention makes use of a simple measurement technique which cannot be used directly at first for the time resolution to be achieved. In this method, an ordinary sampling method is used to detect the received signal (12). An oscillator-like received signal (12) generated by an emitted step-like signal is first sampled during a half-period (14, 15) and is checked with the help of a selection criterion. Only when the result of this check is positive is at least one interpolated or extrapolated contact point (20, 21) of the received signal (12) with a resting level (11) determined in a received signal-time diagram with the help of which the signal transit time or the change in signal transit time is determined.
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18 Claims
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1. A method of measuring a signal transit time in a medical liquid required by a signal to pass through a measurement zone from an ultrasonic transmitter (2) to an ultrasonic receiver (3), in which a line carrying the medical liquid is arranged in the measurement zone, comprising
emitting a step-like signal (10) with the ultrasonic transmitter (2) such that the step-like signal (10) passes through the measurement zone, resulting in an oscillation-like received signal (12) oscillating about a resting level (11) on the ultrasonic receiver (3), the received signal being sampled at regular intervals Δ - t and detected,
checking the oscillator-like received signal (12) on the basis of a selection criterion at least during a half-period (14, 15) to determine whether the oscillator-like received signal (12) is the received signal produced by the step-like signal (10), and when the result of this check is positive, determining the signal transit time or the change in the signal transit time with an interpolated or extrapolated contact point (20, 21) of the oscillator-like received signal (12) with the resting level (11) in a received signal-time diagram. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
- t and detected,
Specification