Op amp investing amplifier derivational and inflectional morphemes
Published 20.03.2020 в Analyse forex euro franc suisse
A method of calculating oxygen saturation from intensity signals resulting from light of first and second wavelengths attenuated by body tissue carrying pulsing blood, comprising: sampling the intensity signals over time; performing a Fourier transform on the sampled intensity signals; and determining oxygen saturation from at least a plurality of magnitudes of the Fourier transformed intensity signals for non-zero frequencies, wherein the step of determining comprises generating a ratio of the Fourier transformed intensity signals for the plurality of magnitudes and selecting at least one peak of ratios, and wherein the selecting at least one peak comprises evaluating the cross correlation between the intensity signals from the first wavelength and the second wavelength.
A method of calculating oxygen saturation from intensity signals resulting from light of first and second wavelengths attenuated by body tissue carrying pulsing blood, comprising: sampling the intensity signals over time; performing a Fourier transform on the intensity signals; and determining oxygen saturation from at least a plurality of magnitudes of the Fourier transformed intensity signals for non-zero frequencies, wherein the step of determining comprises averaging the oxygen saturation over time, and wherein the step of averaging comprises altering the averaging depending upon the level of motion noise in the intensity signals.
A pulse oximeter comprising: a detector that generates intensity signals resulting from light of first and second wavelengths attenuated by body tissue carrying pulsing blood; and a processor that samples the intensity signals over a first time, executes a Fourier transform on the sampled intensity signals, and that calculates oxygen saturation from at least a plurality of magnitudes for each of the Fourier transformed intensity signals for non-zero frequencies during the first time period.
The pulse oximeter of claim 9, wherein the processor calculates oxygen saturation by selecting at least one peak of ratios of the Fourier transformed intensity signals. The pulse oximeter of claim 10, wherein the selected at least one peak corresponds to a peak having the highest oxygen saturation value. The pulse oximeter of claim 11, wherein the processor further determines pulse rate from the frequency of the selected at least one peak.
The pulse oximeter of claim 9, wherein the processor averages oxygen saturation over time. The pulse oximeter of claim 9, wherein the processor calculates oxygen saturation by selecting and averaging a plurality of peaks of ratios of the Fourier transformed intensity signals. A pulse oximeter comprising: a detector that generates intensity signals resulting from light of first and second wavelengths attenuated by body tissue carrying pulsing blood; and a processor that executes a Fourier transform on the intensity signals, and determines oxygen saturation from at least a plurality of magnitudes of the Fourier transformed intensity signals for non-zero frequencies, wherein the processor determines oxygen saturation by selecting at least one peak of ratios of the Fourier transformed intensity signals, and wherein the processor selects at least one peak by evaluating the cross correlation between the intensity signals from the first wavelength and the second wavelength.
A pulse oximeter comprising: a detector that generates intensity signals resulting from light of first and second wavelengths attenuated by body tissue carrying pulsing blood; and a processor that executes a Fourier transform on the intensity signals, and determines oxygen saturation from at least a plurality of magnitudes of the Fourier transformed intensity signals for non-zero frequencies, wherein the processor averages oxygen saturation over time, and wherein the processor varies its averaging depending upon the level of motion noise in the intensity signals.
A method of determining a physiological parameter of pulsing blood, the method comprising: receiving at least first and second intensity signals from a light-sensitive detector which detects light of at least first and second wavelengths propagated through body tissue carrying pulsing blood; transforming said first and second intensity signals to obtain frequency domain data indexed by frequency; selecting a plurality of the frequency domain data corresponding to those non-zero frequencies where the frequency domain data exhibit similar properties; and calculating a physiological parameter of the pulsing blood using at least two of the selected plurality of the frequency domain data.
The method of claim 17, wherein at least one of the properties comprises a ratio of the frequency domain data for the first and second intensity signals. The method of claim 18, wherein the ratio corresponds to blood oxygen saturation of the pulsing blood. The method of claim 19, wherein the selected plurality of the frequency domain data correspond to a highest saturation.
The method of claim 18, wherein said selecting comprises passing the plurality of the frequency domain data for those frequencies at which the frequency domain data exhibit significantly the same ratio. The method of claim 21, wherein the ratio corresponds to blood oxygen saturation of the pulsing blood. The method of claim 17, wherein the physiological parameter comprises pulse rate. The method of claim 23, wherein the selected plurality of the frequency domain data comprise frequency domain data with motion artifacts removed.
The method of claim 17, wherein the physiological parameter comprises a plethysmographic waveform. The method of claim 26, wherein the first transformed series of points correspond to a red intensity signal and the second transformed series of points correspond to an infrared intensity signal, and wherein the plurality of ratios comprise red over infrared magnitude components. A method of determining blood oxygen saturation, the method comprising: receiving at least first and second intensity signals from a light-sensitive detector which detects light of at least first and second wavelengths propagated through body tissue carrying pulsing blood; sampling the first and second intensity signals over a first time period; transforming the sampled first and second intensity signals into first and second sets of spectral domain data; and determining oxygen saturation of the pulsing blood based on more than one indication of the oxygen saturation from each of the first and second sets of spectral domain data for the first time period.
The method of claim 28, wherein the first and second intensity signals include motion induced noise. The method of claim 28, wherein at least one of the first and second sets of spectral domain data comprises frequency domain data. The method of claim 28, wherein one of the more than one indications of the oxygen saturation comprise a plurality of ratios based on information gained by reviewing peaks in at least one of the first and second sets of spectral domain data.
The method of claim 28, wherein one of the more than one indications of the oxygen saturation comprise a plurality of ratios based on information gained by comparing phase information from the first and second sets of spectral domain data. The method of claim 28, wherein one of the more than one indications of the oxygen saturation comprise a plurality of ratios based on information gained by reviewing harmonics in at least one of the first and second sets of spectral domain data.
The method of claim 28, wherein the more than one indications of the oxygen saturation comprise a plurality of ratios. Field of the Invention The present invention relates to the field of signal processing. More specifically, the present invention relates to the processing of measured signals, containing a primary signal portion and a secondary signal portion, for the removal or derivation of either the primary or secondary signal portion when little is known about either of these components.
The present invention is especially useful for physiological monitoring systems including blood oxygen saturation systems. Description of the Related Art Signal processors are typically employed to remove or derive either the primary or secondary signal portion from a composite measured signal including a primary signal portion and a secondary signal portion. For example, a composite signal may contain noise and desirable portions.
If the secondary signal portion occupies a different frequency spectrum than the primary signal portion, then conventional filtering techniques such as low pass, band pass, and high pass filtering are available to remove or derive either the primary or the secondary signal portion from the total signal.
It is often the case that an overlap in frequency spectrum between the primary and secondary signal portions exists. Complicating matters further, the statistical properties of one or both of the primary and secondary signal portions change with time. In such cases, conventional filtering techniques are ineffective in extracting either the primary or secondary signal.
If, however, a description of either the primary or secondary signal portion can be derived, correlation canceling, such as adaptive noise canceling, can be employed to remove either the primary or secondary signal portion of the signal isolating the other portion. In other words, given sufficient information about one of the signal portions, that signal portion can be extracted.
Conventional correlation cancelers, such as adaptive noise cancelers, dynamically change their transfer function to adapt to and remove portions of a composite signal. However, correlation cancelers require either a secondary reference or a primary reference which correlates to either the secondary signal portion only or the primary signal portion only.
For instance, for a measured signal containing noise and desirable signal, the noise can be removed with a correlation canceler if a noise reference is available. This is often the case. Although the amplitude of the reference signals are not necessarily the same as the amplitude of the corresponding primary or secondary signal portions, they have a frequency spectrum which is similar to that of the primary or secondary signal portions.
One area where measured signals comprising a primary signal portion and a secondary signal portion about which no information can easily be determined is physiological monitoring. Physiological monitoring generally involves measured signals derived from a physiological system, such as the human body.
Measurements which are typically taken with physiological monitoring systems include electrocardiographs, blood pressure, blood gas saturation such as oxygen saturation , capnographs, other blood constituent monitoring, heart rate, respiration rate, electro-encephalograph EEG and depth of anesthesia, for example.
Other types of measurements include those which measure the pressure and quantity of a substance within the body such as cardiac output, venous oxygen saturation, arterial oxygen saturation, bilirubin, total hemoglobin, breathalyzer testing, drug testing, cholesterol testing, glucose testing, extra vasation, and carbon dioxide testing, protein testing, carbon monoxide testing, and other in-vivo measurements, for example.
Complications arising in these measurements are often due to motion of the patient, both external and internal muscle movement, vessel movement, and probe movement, for example , during the measurement process. Many types of physiological measurements can be made by using the known properties of energy attenuation as a selected form of energy passes through a medium.
A blood gas monitor is one example of a physiological monitoring system which is based upon the measurement of energy attenuated by biological tissues or substances. Blood gas monitors transmit light into the test medium and measure the attenuation of the light as a function of time. The output signal of a blood gas monitor which is sensitive to the arterial blood flow contains a component which is a waveform representative of the patient's arterial pulse.
This type of signal, which contains a component related to the patient's pulse, is called a plethysmographic wave, and is shown in FIG. Plethysmographic waveforms are used in blood gas saturation measurements. As the heart beats, the amount of blood in the arteries increases and decreases, causing increases and decreases in energy attenuation, illustrated by the cyclic wave s in FIG.
Typically, a digit such as a finger, an ear lobe, or other portion of the body where blood flows close to the skin, is employed as the medium through which light energy is transmitted for blood gas attenuation measurements. The finger comprises skin, fat, bone, muscle, etc.
However, when fleshy portions of the finger are compressed erratically, for example by motion of the finger, energy attenuation becomes erratic. An example of a more realistic measured waveform S is shown in FIG. The primary plethysmographic waveform portion of the signal s is the waveform representative of the pulse, corresponding to the sawtooth-like pattern wave in FIG. The large, secondary motion-induced excursions in signal amplitude obscure the primary plethysmographic signal s.
Even small variations in amplitude make it difficult to distinguish the primary signal component s in the presence of a secondary signal component n. A pulse oximeter is a type of blood gas monitor which non-invasively measures the arterial saturation of oxygen in the blood. In practice, however, the DC voltage has some AC components. The most common source of the AC components is feed through of the AC voltage, such as the 60 Hz spectral components in North America or the 50 Hz frequency common in Europe.
Another source of AC noise is the equipment using the DC power. Still another source of the noise is radio frequency interference. But whatever the source of the AC noise on the power supply output, it is desirable to reduce its magnitude. A power supply's ability to suppress the AC noise on its output is an important performance characteristic of the supply.
Another important measure of power supply performance is the capability to continue delivering stable DC power during disturbances on the AC power line that feeds the power supply. Large capacitors are often connected across DC power supply outputs to improve both AC noise suppression and ride-through capability.
Capacitors perform these functions because they are reservoirs of electrical charges, and can absorb or supply the charges as required. The larger the capacitance of a given capacitor, the better it will suppress AC noise and the longer it will be able to supplement or replace DC power normally provided by the power supply. One type of capacitor that can provide large capacitance is that known to those skilled in the art as a double-layer capacitor. Double layer capacitors can provide previously unattainable large capacitance values in small form factor housings.
For example, a Farad double-layer capacitor can now be made to fit within a battery sized housing, including D-cell sized housings and the like. Connecting a capacitor across a power supply output is not without its own set of problems. In the present context, we focus on three such problems. First, a capacitor may draw a large amount of electrical current on power-up, until the capacitor is sufficiently charged.
This is problematic because the capacitor may keep the voltage of the power supply from reaching its nominal level for an excessive period of time. Power monitoring and power-on reset circuits, common in electronic equipment, may time-out before the voltage stabilizes at the nominal level, keeping the equipment in the reset mode or initiating another start-up sequence of the equipment. Even when the equipment can tolerate a prolonged start-up period, many users find additional waiting annoying.
These problems become worse as capacitance is increased, because higher capacitance allows a capacitor to receive more charge and, therefore, more current from a power supply. Thus, when using high capacitance capacitors, for example, double-layer capacitors, high current draw needs to be considered during the design-in phase even more than before.
It would also be preferable to avoid extensive start-up delays that use of high capacitance capacitors may cause. Second, in some applications excessive current draw may disable the power supply. For example, large current drawn from a power supply can blow a fuse, trip an overload protection circuit, or cause permanent damage to internal components of the power supply. Excessive current draw may also damage the capacitor, causing it to leak, catch fire, or even explode, presenting a safety hazard.
Therefore, it would be desirable to prevent excessive current draw and avoid such possibilities. Third, a typical capacitor failure mode is a short circuit between capacitor terminals. With the capacitor installed across power supply output terminals, the failure would not only affect the AC noise suppression and ride-through capability of the power supply, but would also cause a catastrophic failure because the voltage level output by the power supply would likely fall precipitously, leaving the equipment powered by the supply without adequate power.
It would be beneficial to prevent such catastrophic failures due to capacitor failures. A need thus exists for methods and apparatus to prevent excessive start-up delays caused by charging output capacitors of power supplies. Another need exists to prevent excessive current draw that can disable power supplies during equipment start-up.
Yet another need exists to prevent capacitor failures from causing catastrophic equipment failures. A further need exists to implement such solutions with high capacitance capacitors such as double-layer capacitors. One circuit in accordance with the invention includes a current-sensing resistor, and a switch with a pair of outputs and an input. The outputs of the switch are coupled in series with the energy storage device and with the current-sensing resistor, forming a series combination.
The combination series is in turn coupled across the output of the power supply. In one embodiment, the energy storage device comprises high capacitance capacitors such as double-layer capacitors. The input of the switch receives a switching signal that controls the state of the switch.
When the switching signal is at a first level, the switch assumes a conducting on state with low resistance between the switch's outputs; when the switching signal is at a second level, the switch assumes a non-conducting off state with high resistance between the outputs of the switch. The circuit further includes a differential high-gain device, such as a comparator or an operational amplifier. An output of the differential high-gain device is coupled to the input of the switch, so as to control the state of the switch and the charging current flowing through the switch and other components of the series combination.
A non-inverting input of the differential high-gain device is biased by a control voltage generated, for example, by a voltage divider coupled across the output of the power supply. An inverting input of the differential high-gain device receives a feedback voltage generated by the charging current flowing through the current-sensing resistor.
The output of the differential high-gain device drives the input of the switch with the switching signal at the first level when the control voltage exceeds the feedback voltage by an input offset voltage of the differential high-gain device. The differential high-gain device drives the input of the switch with the switching signal at the second level when the feedback voltage exceeds the control voltage by the input offset voltage.
In this way, the charging current that the energy storage device can draw from the power supply is limited to a level determined by the values of the current-sensing resistor, the resistors of the voltage divider, and the voltage level at the output of the power supply.
Another circuit in accordance with the invention includes a switch with a pair of outputs and an input. The switch's outputs are coupled in series with an energy storage device to form a first series combination, which combination is coupled across the output of the power supply.
By bringing together all aspects of microsystem design, it can be expected to facilitate the training of not only a new generation of engineers, but perhaps a whole new type of engineer — one capable of addressing the complex range of problems involved in reducing entire systems to the micro- and nano-domains.
| Bitcoins explained vimeo pro | Description of the Related Art Signal processors are matthews investing employed to remove or derive either the primary or secondary signal portion from a composite measured signal including a primary signal portion and a secondary signal portion. When the switching signal is at a first level, the switch assumes a conducting on state with low resistance between the switch's outputs; when the switching signal is at a second level, the switch assumes a non-conducting off state with high resistance between the outputs of the switch. The combination series is in turn coupled across the output of the power supply. The pulse oximeter of claim 9, wherein the processor calculates oxygen saturation by selecting op amp investing amplifier derivational and inflectional morphemes averaging a plurality of peaks of ratios of the Fourier transformed intensity signals. In one embodiment, the feedback portion provides a positive feedback signal. The separator prevents an electronic as opposed to an ionic current from shorting the two electrodes. |
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| Automotive engine lubrication basics of investing | Pulse oximetry involves determining the saturation of oxygen in the blood. The processor of the present invention may also remove the secondary signal portions from the measured signals yielding a primary reference which is a combination of the remaining source signal portions. This is problematic because the capacitor may keep the voltage of the power supply from reaching its nominal level for an excessive period of time. A need thus exists for methods and apparatus to prevent excessive start-up delays caused by charging output capacitors of power supplies. The combination series is in turn coupled across the output of the power supply. For example, the device assumes a conductive state when the output of the differential high-gain device is at a high voltage level. |
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Published 20.03.2020 в Analyse forex euro franc suisse
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