Seppo Nissilä

Non-invasive blood pressure measurement based on the electronic palpation method

The most commonly used methods of non-invasive blood pressure monitoring are the auscultation method and the oscillometric method. Although both methods are generally accepted and widely used, they are reportedly inaccurate and irreproducible in terms of specific hypertension screening and control. Here, the authors present a new electronic palpation method based on an arm cuff and a wrist watch type pulse sensor, which they have developed and tested. The results show that this method is more accurate than the auscultation and oscillometric methods. The difference relative to an intra-arterial measurement was -0.8/spl plusmn/4.6 mmHg for systolic values and -1.5/spl plusmn/5.0 mmHg for diastolic values. Moreover, the correlation coefficient of 0.81 was higher than the corresponding figures for the auscultation and oscillometric methods: 0.60 and 0.55, respectively.

Production and detection theory of pulsed photoacoustic wave with maximum amplitude and minimum distortion in absorbing liquid

The photoacoustic effect produced by laser-induced stress waves in liquids has found a variety of scientific and practical applications in industry, medicine, and environmental protection. The photoacoustic technique has the natural advantage of being less sensitive to scattering than traditional optical tools, thus offering increased accuracy and sensitivity. This paper aims to give a systematic outline of photoacoustic techniques, starting with the production and extending to the propagation and detection of photoacoustic waves. The focal point is the production of acoustic waves with maximum amplitude and minimum distortion. Maximum amplitude plays an essential role in photoacoustic spectroscopy and minimum distortion is the key to the determination of optical distribution and imaging in turbid media.

Thermal characteristics of optical delay in fibers used in pulsed laser rangefinding

The transit times of light pulses as functions of temperature in nylon and acryl-coated fibers and hard-clad silica (HCS) fibers are analyzed theoretically and compared with the measured results. The effect of temperature on the transit time can be explained in terms of generally known models and the physical and thermal coefficients of the materials. The thermal effect in a core-cladding interface can have unpredictable consequences, however, as in HCS fibers. Because of the increased inhomogeneities at the interface of the core-cladding, the transit time of a light pulse increases, in contrast to that in a glass fiber, at lower temperatures. Thus the light pulses have larger angles of propagation than is shown by the numerical aperture of the fiber, and at the same time the attenuation of the fiber increases. >

Intensity Modulated Fiber Optic Sensors For Robot Feedback Control In Precision Assembly

Fiber optic reflectance sensors, mounted on a gripper, have been constructed for a scara-type robot in the insertion of electronic components. The position of the gripper fingers, the distance to the object component, the edges, the orientation and the pin images are meas-ured and determined during the assembly process. The sensor consists of a transmitter (LED, 850 nm) and a receiver, (PIN-photodiode), which are equipped with different fiber optic measurement heads according the kind of application. The emitters and detectors are con-nected to optical fibers using mounts and SMA connectors. The position sensors of the gripper fingers are used to measure the distance between the gripper body and the fingers. The measurement range of the position sensor is 17 mm and the resolution is better than 50 pm using 100 Hz bandwidth. The measured position information is used to control the gripper dc-motor drive via a I/O controller. Proximity sensors mounted on the ejector are used to measure the distance to the object component and detect the edges. Based on measured scan profiles of components (capacitor, inductor) the edges can be determined. A typical transition range of an edge is < 2 mm giving a position resolution better than 50 pm. This edge information is used for orientation calculations. The separate pin image sensor station is used to measure the reflectance scan profiles of the pins of the component to determine the span of the component pin relative to the robot gripper. The xy-motion of the robot is used for scanning at a constant velocity. The position of the tip of the pin can be determined in the xy-plane to an accuracy greater than ± 50 μm. The realization of the sensors together with experimental results are presented.

A High Resolution Reflectometer for Measuring Dynamic Strain in a Single Mode Optical Fibre

A high resolution, pulsed time-of-flight (TOF) reflectometer for measuring length and dynamic strain in a single mode optical fibre is reported. The object of the paper is to discuss the measurement principle and to present the results of some practical experiments, including a pull test on an OPGW cable and an elongation test on a standard telecommunication fibre with a dual-acrylate coating. Applications in the field of optical fibre-based strain sensing are also briefly reviewed.

Real-time detection of premature ventricular contraction using a matched filter bank

We have investigated the detection of premature ventricular contraction and designed a digital signal processing algorithm to detect them. The method is based on the use of a matched filter bank.

Experiences from Embedded Optical Fiber Based Cure and Stress Sensing in Composite Structures

We report here on experiencies with optical fiber embedding and cure monitoring in a composite container manufacturing process, and with external stress measurements. Microbending loss in long single-mode and multi-mode telecommunication fibers was investigated. The measurements were carried out using the optical through power technique and a commercial optical time domain reflectometer. Simple miniature size electronics, applicable even for embedding was developed for example as an alarm indicator. We found that the coating material and its thickness have an effect on loading sensitivity and on the applicability of the method for cure monitoring. Though we discovered that repeatability issues are a problem, the measurement data indicate that the end of the curing process of the composite can be determined by optical sensing fibers. Further, sensing fibers in different wall layers can be used to follow the progress of the curing inside the wall at different depths. The response of damaging external loading on the structure can also be detected.

On the use of optical fibres in a pulsed time-of-flight laser rangefinder

The pulsed time-of-flight laser rangefinding technique has been used in many industrial measurement applications, including 3D-coordinate measuring devices, hot surface profilers and mobile robot sensors. Optical fibres, typically 1-10 m in length and 100-400 μm in diameter can be used to guide optical pulses to the separate sensing head of the measurement device. The use of a large multimode fibre may cause problems, however, when aiming at millimetre accuracy, as the construction and adjustment of the optics of the sensor head may affect the transit time linearity and measurement accuracy via multimode dispersion. Environmental effects, such as bending, vibration due to the moving sensing head and temperature, also cause measurement errors. The error sources are studied and characterized in this paper