Abstract: A sensor element for detecting solid particles in a fluid includes: a detecting unit including a piezoelectric film consisting essentially of a ceramic material, a first electrode coated onto at least a portion of the outer surface of the piezoelectric film, and a second electrode coated onto at least a portion of the inner surface of the piezoelectric film; a vibrating portion consisting essentially of a second ceramic material, the detecting unit being placed on the vibrating portion so that the second electrode is coated onto at least a portion of the vibrating portion; and a fixing portion for fixing the vibrating portion so that the vibrating portion may vibrate. At least one of the detecting unit and the vibrating portion contacts with a solid particle in the fluid so that the piezoelectric film converts the vibration into an electric signal. A particle sensor includes the sensor element. The sensor element and the particle sensor are excellent in particle detection precision and durability at low cost.

Abstract: A sensor element for detecting solid particles in a fluid includes: a detecting unit including a piezoelectric film consisting essentially of a ceramic material, a first electrode coated onto at least a portion of the outer surface of the piezoelectric film, and a second electrode coated onto at least a portion of the inner surface of the piezoelectric film; a vibrating portion consisting essentially of a second ceramic material, the detecting unit being placed on the vibrating portion so that the second electrode is coated onto at least a portion of the vibrating portion; and a fixing portion for fixing the may vibrate portion so that the vibrating portion vibrates. At least one of the detecting unit and the vibrating portion contacts-with a solid particle in the fluid so that the piezoelectric film converts the vibration into an electric signal. A particle sensor includes the sensor element. The sensor element and the particle sensor are excellent in particle detection precision and durability at low cost.

Abstract: A non-invasive aortic blood flow sensor is disclosed. The sensor determines the blood flow in the aorta of a patient based on the pressure difference between the right and left subclavian arteries. The pressure of the subclavian arteries is non-invasively measured by determining the blood pressures in the arteries of the patient's right and left arms by means of tonometric blood pressure sensors. The signals from the tonometric sensors are first equalized to account for any pressure waveform distortion due to propagation of the pulse from the aorta to the sensor locations. Next, a correction is made for DC offset. The modified pressure signals are then compared, and the pressure difference determined. The blood flow is determined from the pressure difference by known pressure/flow relationships.

Abstract: A pulse rate sensor system is packaged in a wristwatch sized assembly and is worn by the user to provide an accurate determination of pulse rate. A tonometer sensor is provided to detect heartbeat pressure waves produced by a superficial artery. A microcomputer manipulates the unprocessed tonometer sensor element signals using multiple algorithms to determine an accurate pulse rate.

Abstract: A tonometric blood pressure monitoring system is disclosed having a variable extension sensor assembly. The sensor assembly is connected to a central control unit through separable pod elements. Within the pod elements are a master cylinder and drive system for varying the extension of blood pressure sensor from the sensor assembly. The blood pressure sensor is mounted at the end of an sensor piston, the movement of which is guided on a central rod. The sensor assembly also includes a rolling bellows arrangement for providing a variable hold-down pressure between a cavity block and the sensor assembly housing. The blood pressure sensor is moved laterally, in one embodiment, to provide optimum lateral placement of the sensor with respect to a target source of blood pressure information such as the radial artery of the subject.

Abstract: A method and apparatus for determining and compensating for the crosstalk behavior and element spacing of an arterial tonometer sensor in order to obtain a more accurate blood pressure measurement. The crosstalk behavior and the effects of element spacing in a tonometer sensor having a plurality of sensing elements located on a single diaphragm is derived using advanced modeling techniques. An error correction factor look-up table is computed and applied to an uncorrected blood pressure measurement, resulting in increased accuracy.

Abstract: A system for positioning a tonometric sensor array over an artery on a patient's wrist such that minimal hold down pressure is required to flatten said artery. The preferred embodiment of the invention comprises a sensor case which can be attached to a patient's wrist in a manner similar to a conventional wristwatch. A transducer piston is received in the case and is movable therein. A protrusion in the lower face of the transducer piston defines a sensor mounting platform. A sensor comprising an array of pressure sensing elements is attached to the mounting platform such that the operative face of the sensor is offset from the lower surface of the piston by a predetermined distance. The sensor platform has a shape which allows part of it to fit between the radius bone and the flexor tendon in the patient's wrist. The required hold down pressure is provided by a pressurizable bellows.

Abstract: The invention comprises a vehicle load sensor apparatus for measuring the load on one or more spindles of a vehicle axle which comprises a vehicle axle spindle, a string or wire is attached to the vehicle spindle, and a means for measuring the change of tension in the string. The tension in the string is measured by inducing a vibration in the string and then measuring the frequency of vibration of the string which is proportional to the square root of the tension in the string. The change of tension is then determined by comparing this measured tension in the string to the tension in the string previously measured under no-load conditions.

Abstract: Intraarterial blood pressure is measured noninvasively by an electromechanical transducer (22) that includes an array of transducer elements (22-1 through 22-19). The transducer extends across an artery (24) with transducer elements at the ends of the array extending beyond opposite edges of the artery. A set of diastolic and/or systolic pressure and pulse amplitude values is obtained from the outputs from the transducer elements, which values are stored in computer (62). Information concerning the subject related to the diameter of the underlying artery including, for example, the subject's age, weight, arm and wrist diameter also is entered into computer (62) through keyboard (64), from which information an estimation of the diameter of the underlying artery is obtained. Using the set of pulse amplitude values, a transducer element at the center of a search area located substantially at the center of the artery is identified.

Abstract: Intraarterial blood pressure is measured noninvasively by an electromechanical transducer. The correct hold-down force to be applied to the transducer for obtaining accurate blood pressure measurements is determined by obtaining a set of at least one of the diastolic pressure, systolic pressure, and pulse amplitude versus hold-down pressure values over a range of hold-down pressures between which the underlying artery is unflattened and it is occluded. A polynomial is fitted to at least one of the sets of values, from which polynomial the correct hold-down pressure is determined. The hold-down pressure at the point of minimum slope of graphs of the polynominals fitted to the systolic and diastolic versus hold-down pressure values provides an indication of the correct hold-down pressure.

Abstract: In a capacitance type displacement measuring instrument, wherein a change in electric capacitance between electrodes due to a relative displacement between two members movable relative to each other is detected on the basis of a change in phase of a detection signal, and a relative displacement between the two members is measured from the change in phase, square waveform signals are applied in inversed phase to two transmitting electrodes provided on one of the members and signals induced on two wave pattern electrodes provided on the other of the members are received by receiving electrodes provided on the first of the members. Outputs from the receiving electrodes are successively taken in by a multiplexer, and then the amplitude-modulated square wave signals, outputted from the multiplexer, are demodulated. A phase detector measures the phase of the demodulated waveform, thereby measuring the relative displacement on the basis of change in phase.

Abstract: A capacitance type displacement measuring instrument is disclosed in which a change in electric capacity between electrodes due to a change in displacement between two members movable relative to each other is detected on the basis of a change in phase of a detection signal and a displacement value between the two members is measured from the change in the capacity. AC signals are successively applied to transmitting electrodes provided on one of the members at a predetermined pitch by a multiplexer and signals induced in transfer electrodes at a predetermined pitch differing from the aforesaid pitch of the transmitting electrodes are received by pickup electrodes provided on the aforesaid one of the members. The relative displacement is detected from a change in phase of a received signal of substantially triangular waveform, which are obtained by the pickup electrode.

Abstract: Intra-arterial blood pressure is noninvasively measured and monitored by an electromechanical force sensor which is made up of an array of individual pressure or force sensing elements, each of which has at least one dimension smaller than the lumen of the underlying artery wherein blood pressure is to be measured, and the individual pressure sensitive element used to monitor blood pressure is within one artery's diameter of the pressure sensitive element that generates the waveform of maximum pulse amplitude and generates a waveform having a spatially local minimum of at least one of the diastolic and systolic pressures.

Abstract: An A.C. powered amplifier for converting low power information input signals to corresponding signals of a substantially increased power level without requiring a power transformer. A signal processor having a low power information signal input and a feedback signal input controls the state of a controllable switch. The switch power input is coupled to a source of relatively high A.C. voltage via a rectifier circuit and a first low pass filter circuit, and the switch output is coupled to the amplifier output terminal via a second low pass filter circuit. A feedback path is provided from either the switch output or the amplifier output terminal to the feedback signal input of the signal processor. The signal processor may comprise a pulse width, or pulse frequency modulation circuit.The amplifier provides high efficiency, low power loss, and has a band width limited only by the maximum switching frequency of the controllable switch.