Image pmeter t.jpg thumb right 238px S Meter of a Ten Tec Orion amateur radio transceiver. An S meter signal strength meter electronics meter is an indicator often provided on communications receiver s, such as amateur radio receivers or shortwave broadcast receivers. The scale markings are derived from a subjective system of reporting signal strength from S1 to S9 as part of the RST code . The term S unit can be used to refer to the amount of signal strength required to move an S meter indication from one marking to the next. IARU Region 1 Technical Recommendation R.1 The International Amateur Radio Union IARU Region 1 agreed on a technical recommendation for S Meter calibration for High frequency HF and Very high frequency VHF Ultra high frequency UHF transceivers in 1981. ref name iaru standard International Amateur Radio Union Region I 1981 . http www.algonet.se k jarl ssa IARU smeter.html IARU Region 1 Technical Recommendation R.1 . Brighton, England, UK. ref IARU Region 1 Technical Recommendation R.1 defines S9 for the HF bands to be a receiver input power of 73 dBm . This is a level of 50 volt microvolts at the receiver s antenna input assuming the input Electrical impedance impedance of the receiver is 50 Ohm unit ohms . For VHF bands the recommendation defines S9 to be a receiver input power of 93 dBm . This is the equivalent of 5 microvolts in 50 ohms. The recommendation defines a difference of one S unit corresponds to a difference of 6 decibel s dB , equivalent to a voltage ratio of two, or power ratio of four. Signals stronger than S9 are given with an additional dB rating, thus S9 20dB , or, verbally, 20 decibels over S9 . Examples A weak signal with signal strength of S2 corresponds to received power of 115 dBm or 0.40 microvolts in 50 ohms on HF. A strong signal with signal strength of S8 corresponds to received power of 79 dBm or 25 microvolts in 50 ohms on HF. Some signal generators are calibrated in dB above 1uV and have an output in emf. For exam ... more details
Input offset voltage math V os math is the differential amplifier differential DC voltage required between the inputs of an amplifier , especially an operational amplifier , to make the output zero 0 volts with respect to ground, or between differential outputs if they exist, for voltage amplifiers . ref cite book title Fundamentals of Analog Circuits last Floyd first Thomas L. coauthors Buchla, David year 1998 publisher Prentice Hall isbn 013836933X url http books.google.com books?id iu4LAAAACAAJ&d ref Typical values are around 1 10mV for cheap commercial grade operational amplifier integrated circuits , but can be a few microvolts if nulled assuming the IC has offset null pins for external adjustment circuits and or if higher quality perhaps laser trimmed devices are used, although this may drift with temperature or age. Chopper amplifiers are used to reduce offset voltages. Input current and input offset current will affect the offset voltage unless low impedance signal sources are used FET input operational amplifiers tend to be better in this respect. References reflist Category Electrical parameters electronics stub de Offset Spannung it Tensione di offset ja ... more details
Orphan date July 2009 Infobox VG collapsible state show image image File Haveonlinelogo.jpg caption aspect ratio resolution developer TOT Thailand TOT GungHo Online Entertainment publisher SK iMedia distributor engine Gamebyro with PhysX version released vgrelease new TWN November 2009 NA TBA genre Third Person Shooter modes Multiplayer platforms Personal computer PC media Download requirements Minimum br CPU 1.4 GHz br RAM 512 MB br GPU GeForce FX 5700 br HDD 600 MB input Mouse Mouse Computing And Keyboard H.A.V.E. Online lang ko , Japanese H.A.V.E , MicroVolts in the English version is a multiplayer online shooter game being developed by Korean company SK iMedia . Currently, only the Taiwan and Thai versions are available, with an English version being made by Rock Hippo. Hosting There has been no word on a South Korea Korean publisher for this game until Gravity Corp announced that it will publish the game in Korea . The company has also announced a Japan Japanese version. No release date has ben set, though. Chinese video game company , Insrea, has hosted the game in Taiwan. It is currently in open beta . TOT is also publishing the game in Thailand . Rock Hippo announced that it will publish the game in English territories under the name, MicroVolts . Plagiarism In 2009, the game has been criticized for its strong similarity to Team Fortress 2 , a multiplayer first person shooter . ref cite web url http kotaku.com 5306691 korean pc game rips off team fortress 2 title Korean PC Game Rips Off Team Fortress 2 date July 2, 2009 accessdate 2010 ref ref cite web url http kotaku.com 5308073 korean developer responds to team fortress 2 rip off claims title Korean Developer Responds to Team Fortress 2 Rip Off Claims date July 6, 2009 accessdate 2010 ref References reflist External links http www.haveol.com.tw Official Taiwan Site http www.sk imedia.com Company site http www.have.in.th Official Thai Site http www.microvolts.com Official English Site http www.to ... more details
Unreferenced stub auto yes date December 2009 The extracellular field potential is the electrical potential produced by Cell biology cell s, e.g. Neuron nerve or Muscle fiber muscle cell s, outside of the cell. Electrophysiology Electrophysiological studies investigate these potentials using extracellular microelectrode s. In these experiments the extracellular field potential will be detected as an electrical potential whose source and composition is often ambiguous, making its interpretation difficult. Individual nerve cells neuron s may produce Voltage spike spike s seen as peaks of some tens to hundreds of microvolts. Contributions from neighbouring neurons may overlap, producing extracellular potentials of up to several millivolts. Spatially integrating over even larger populations of cells, i.e. lumps of nervous tissue nervous or muscle muscular tissue , will produce signals commonly called local field potential s LFP that can be recorded either in the tissue or with suitable equipment at the body surface as, e.g., electroencephalogram EEG , electrocardiogram ECG , or electromyogram EMG . For individual cells, the time course of the extracellular potential theoretically is inversely proportional to the transmembrane current. In practice, however, this is complicated considerably by the very complex Morphology biology morphology of neurons and the overlap of contributions from adjacent cells. See also Local field potential DEFAULTSORT Extracellular Field Potential Category Cell biology Category Electrochemistry Category Electrophysiology Category Membrane biology Category Physical quantities Biology stub ... more details
Noise in audio, recording, and broadcast systems refers to the residual low level sound usually hiss and hum that is heard in quiet periods of a programme. In audio engineering it can refer either to the acoustic noise from loudspeakers, or to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as hiss . This signal noise is commonly measured using A weighting or ITU R 468 noise weighting ITU R 468 weighting Noise is often generated deliberately and used as a test signal . Two types of deliberately generated noise in common use are referred to as white noise , which has a uniform spectral power density at all frequencies, or pink noise which has a power spectral density that falls at 3dB octave with rising frequency. The latter is often more useful in audio testing because it contains constant energy per octave and hence per commonly used 1 3rd octave , rather than a prepondance of energy at high frequencies. In other words it contains energy that is distributed geometrically rather than linearly. See also Noise Noise music Noise music Noise measurement quiescent Noise electronics signal to quantization noise ratio ITU R 468 noise weighting A weighting Weighting filter Equal loudness contour External links http www.sengpielaudio.com calculator noise.htm White noise calculator, thermal noise Voltage in microvolts, conversion to noise level in dBu and dBV and vice versa Noise Category Noise Audio Category Audio electronics ... more details
strength measured 300 meters from the antenna may not exceed 2400 microvolts per meter divided by the frequency in kilohertz, or approximately 17 microvolts per meter. Australia The Australian ... more details
Image Westoncell Volt.jpg right The Weston cell , invented by Edward Weston chemist Edward Weston in 1893, is a wet cell wet chemical cell that produces a highly stable voltage suitable as a laboratory standard for calibration of voltmeter s. It was adopted as the International Standard for electromotive force EMF between 1911 and 1990. Chemistry The anode is an amalgam chemistry amalgam of cadmium with mercury element mercury , the cathode is of pure mercury, the electrolyte is a solution of cadmium sulfate cadmium sulfate octahydrate and the depolarizer is a paste of mercurous sulfate . As shown in the illustration, the cell is set up in an H shaped glass vessel with the cadmium amalgam in one leg and the pure mercury in the other. Electrical connections to the cadmium amalgam and the mercury are made by platinum wires fused through the lower ends of the legs. Characteristics The original design was a saturated cadmium cell producing a convenient 1.018638 Volt reference and had the advantage of having a lower temperature coefficient than the previously used Clark cell . ref Robert B. Northrop Introduction to instrumentation and measurements 2nd ed CRC Press, 2005 ISBN 0849337739 page 14 ref Reference cells must be applied in such a way that no current is drawn from them. The temperature coefficient can be reduced by shifting to an unsaturated design, the predominant type today. However, an unsaturated cell s output decreases by some 80 microvolts per year, which is compensated by periodic calibration against a saturated cell. Dr. F.A. Wolff, NBS Researcher and 1st Chair of the Washington AIEE Section contributed significant research to the studies of the Weston Cell. ref Bulletin of the Bureau of Standards , November 1908, volume 5, number 2, pp. 309 337 ref References references Literature Practical Electricity by W. E. Ayrton and T. Mather, published by Cassell and Company, London, 1911, pp 198 203 US patent 494827 , Voltaic cell http ts.nist.gov MeasurementServ ... more details
Virtual ground or virtual earth is a node of the circuit that is maintained at a steady reference potential, without being connected directly to the reference potential. In some cases the reference potential is considered to be that of the surface of the earth, and the reference node is called ground or earth as a consequence. The virtual ground concept aids circuit analysis in operational amplifier and other circuits and provides useful practical circuit effects that would be difficult to achieve in other ways. In circuit theory, a node may have any value of current or voltage but physical implementations of a virtual ground will have limitations of current handling ability and a non zero Electrical impedance impedance which may have practical side effects. Construction A voltage divider , using two resistors, can be used to create a virtual ground node. If two voltage sources are connected in series with two resistors, it can be shown that the midpoint becomes a virtual ground if math frac V 2 V 1 frac R 2 R 1 math br style clear both Image opampinverting.svg right thumb 280px Op amp inverting amplifier An active virtual ground circuit uses an op amp or some other circuit element that has gain. Since an operational amplifier has very high open loop gain, the potential difference between its inputs tend to zero when a feedback network is implemented. To achieve a reasonable voltage at the output and thus equilibrium in the system , the output supplies the inverting input via the feedback network with enough voltage to reduce the potential difference between the inputs to microvolts. The non inverting input of the operational amplifier is grounded therefore, its inverting input, although not connected to ground, will assume a similar potential, becoming a virtual ground . Applications Voltage is a differential quantity, which appears between two points. In order to deal only with a voltage an electrical potential of a single point, the second point has to be connect ... more details
Infobox laboratory equipment name image URM25d SignalGenerator.jpg alt caption URM 25 Signal Generator c. 1955 acronym other names uses Aligning antique radio equipment notable experiments inventor manufacturer Various, commissioned by U.S. Military model 25D related The AN URM 25 Signal Generator was a device used during the 1950s and 1960s by the U.S. Military to test electronics electronic equipment. History The AN URM 25 were part of a series of vacuum tube based signal generators built for the U.S. Military during the Cold War era. Today they are collected and used by vintage amateur radio , antique radio and boat anchor enthusiasts who say they provide a reasonably high accuracy and stability for a low cost with build quality reflecting tough military construction standards. ref name r 390a.net http www.r 390a.net Pearls URM 25.pdf R 390a.net , URM 25x discussions ref Specifications Image URM25D SignalGenerator FreqMeter.jpg thumb 150px right w Freq. Meter RF Radio Frequency can be varied between 10 kHz and 50 MHz with modulation selectable at 400 and 1,000 Hz. RF level from .1 to 100,000 microvolts or 2 volts is available depending upon termination load. Output impedance is 50,500 ohms. Carrier oscillation is performed by 6AH6 with an additional 6AH6 buffer stage followed by a 6AG7 output amplifier. Modulation oscillations at 400 and 1,000 Hz are provided by 5814A . URM 25x models also contain internal VTVM Voltmeter Vacuum Tube Voltmeter .28VTVM.29 vacuum tube voltmeter and crystal calibration. The carrier frequency can be set by interpolation using the graduated dial. Additionally, the URM 25 s have a BNC connector BNC jack for constant 200 mV output that can be connected to a frequency meter to eliminate guesswork. A sufficient warm up period is required to ensure the best stability at higher frequencies. The cabinet cover includes accessories such as an impedance adapter, fixed attenuator and antenna simulator. Additional accessory kit ... more details
Image Maximal Response ERG.png thumb 325px Maximal response ERG waveform from a dark adapted eye. File Electroretinogram.jpg thumb 325px A patient undergoing an electroretinogram Electroretinography measures the electrical responses of various cell types in the retina , including the Photoreceptor cell photoreceptors rod cell rods and cone cell cones , inner retinal cells bipolar cell bipolar and amacrine cell amacrine cells , and the ganglion cell s. Electrode s are usually placed on the cornea and the skin near the human eye eye , although it is possible to record the ERG from skin electrodes. During a recording, the patient s eyes are exposed to standardized stimulus physiology stimuli and the resulting signal is displayed showing the time course of the signal s amplitude voltage . Signals are very small, and typically are measured in microvolts or nanovolts. The ERG is composed of electrical potentials contributed by different cell types within the retina, and the stimulus conditions flash or pattern stimulus, whether a background light is present, and the colors of the stimulus and background can elicit stronger response from certain components. If a flash ERG is performed on a dark adapted eye, the response is primarily from the rod cell rod system . Flash ERGs performed on a light adapted eye will reflect the activity of the cone cell cone system . Sufficiently bright flashes will elicit ERGs containing an a wave initial negative deflection followed by a b wave positive deflection . The leading edge of the a wave is produced by the photoreceptors, while the remainder of the wave is produced by a mixture of cells including photoreceptors, bipolar cell bipolar , amacrine cell amacrine , and Muller cells or Muller glia . ref http webvision.med.utah.edu ERG.html The 20origin 20of 20the 20major 20ERG 20waves Webvision at University of Utah ref The pattern ERG, evoked by an alternating checkerboard stimulus, primarily reflects activity of retinal ganglion cells. Cl ... more details
Image Voltmeter hg.jpg thumb Demonstration voltmeter from a physics class A voltmeter is an instrument used for measuring the electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit digital voltmeters give a numerical display of voltage by use of an analog to digital converter . Voltmeters are made in a wide range of styles. Instruments permanently mounted in a panel are used to monitor generators or other fixed apparatus. Portable instruments, usually equipped to also measure current and resistance in the form of a multimeter , are standard test instruments used in electrical and electronics work. Any measurement that can be converted to a voltage can be displayed on a meter that is suitably calibrated for example, pressure, temperature, flow or level in a chemical process plant. General purpose analog voltmeters may have an accuracy of a few percent of full scale, and are used with voltages from a fraction of a volt to several thousand volts. Digital meters can be made with high accuracy, typically better than 1 . Specially calibrated test instruments have higher accuracies, with laboratory instruments capable of measuring to accuracies of a few parts per million. Meters using amplifier s can measure tiny voltages of microvolts or less. Part of the problem of making an accurate voltmeter is that of calibration to check its accuracy. In laboratories, the Weston Cell is used as a standard voltage for precision work. Precision voltage references are available based on electronic circuits. Analog voltmeter Image Galvanometer diagram.svg thumb A moving coil galvanometer of the d Arsonval type. ul li font face arial color red The red wire carries the current to be measured. font li li font face arial color green The restoring spring is shown in green. font li li N and S are the north and south poles of the magnet. li ul A moving coil galvanometer can be used as ... more details
other uses Gain disambiguation In electronics , gain is a measure of the ability of a electrical network circuit often an amplifier to increase the Power physics power or amplitude of a Signal electrical engineering signal from the input to the output. It is usually defined as the mean ratio of the Signalling telecommunication signal output of a system to the Signalling telecommunication signal input of the same system. It may also be defined on a logarithmic scale, in terms of the decimal logarithm of the same ratio decibel dB gain . A gain greater than one zero dB , that is, amplification , is the defining property of an active component active electronic component or circuit, while a passive circuit will have a gain of less than one. Thus, the term gain on its own is ambiguity ambiguous . For example, a gain of five may imply that either the voltage , current or the Electric power power is increased by a factor of five, although most often this will mean a voltage gain of five for audio and general purpose amplifier s, especially operational amplifiers , but a power gain for Radio frequency RF amplifiers, and for directional aerials will refer to a signal power change compared with a simple dipole. I should check that latter clause in an ARRL handbook Furthermore, the term gain is also applied in systems such as sensor s where the input and output have different units in such cases the gain units must be specified, as in 5 microvolts per photon for the responsivity of a photosensor. The gain of a bipolar transistor normally refers to forward current transfer ratio, either h sub FE sub Beta , the static ratio of I sub c sub divided by I sub b sub at some operating point , or sometimes h sub fe sub the small signal current gain, the slope of the graph of I sub c sub against I sub b sub at a point . In laser physics , gain may refer to the increment of power along the beam propagation in a gain medium , and its dimension is m sup 1 sup inverse meter or 1 meter. Loga ... more details
Expand German Ernst Fleischl von Marxow date June 2010 Image Fleischl marxow 2.jpg thumb right Ernst von Fleischl Marxow Ernst von Fleischl Marxow , aka Ernst Fleischl von Marxow 1846 &ndash 1891 was an Austrian physiology physiologist and physician who became known for his important investigations on the electrical activity of nerve s and the brain . He was also a creative inventor of new devices which were widely adopted in clinical medicine and physiological research. Marxow studied medicine in the University of Vienna , Austria . He started his scientific career as a research assistant in the laboratory of Ernst Wilhelm von Br cke 1819 1892 , and later as an assistant, in the same University, to the eminent pathologist Carl Freiherr von Rokitansky Carl von Rokitansky 1804&ndash 1878 . Unfortunately, an accident while he was conducting an autopsy infected one of his fingers, which had to be amputated and interrupted his activities in anatomical pathology . Thus, he had to turn to Physiology, and he came back to von Br cke s laboratory in Vienna after studying for a year with Carl Ludwig 1816&ndash 1895 , another famous physiologist at the University of Leipzig , Germany , obtaining his doctoral degree in Medicine in 1874. In the first phase of his career in neurophysiology , Marxow dedicated himself to electrophysiology of nerve s and muscle s, then a research field of increasing prestige, after the pioneering investigations of Emil du Bois Reymond 1818&ndash 1896 , who had discovered the action potential s of axon s. This field highly benefitted from the technical developments occurring in the physics physical sciences , particularly new devices which were invented to work with small electric potential s and electric current currents . Since biological tissue s have extremely low levels of electrical activity in the range of microvolts , neurophysiology s progress had to wait for them. Like many German physiologists of his time, Marxow had a good knowledge and a ... more details
An evoked potential or evoked response is an electrical potential recorded from the nervous system of a human or other animal following presentation of a Stimulus physiology stimulus , as distinct from spontaneous potentials as detected by electroencephalography EEG or electromyography EMG . Evoked potential amplitude s tend to be low, ranging from less than a microvolt to several microvolts, compared to tens of microvolts for EEG, millivolts for EMG, and often close to a volt for Electrocardiogram ECG . To resolve these low amplitude potentials against the background of ongoing EEG, ECG, EMG and other biological signals and ambient noise, signal averaging is usually required. The signal is time locked to the stimulus and most of the noise occurs randomly, allowing the noise to be averaged out with averaging of repeated responses. ref Cite book title Spehlmann s Evoked Potential Primer author Karl E. Misulis, Toufic Fakhoury year 2001 publisher Butterworth heinemann isbn 0750673338 ref Signals can be recorded from cerebral cortex , brain stem , spinal cord and Peripheral nervous system peripheral nerve s. Usually the term evoked potential is reserved for responses involving either recording from, or stimulation of, central nervous system structures. Thus evoked compound motor action potentials CMAP or sensory nerve action potentials SNAP as used in nerve conduction study nerve conduction studies NCS are generally not thought of as evoked potentials, though they do meet the above definition. Sensory evoked potentials Sensory evoked potentials SEP are recorded from the central nervous system following stimulation of sense organ s for example, visual evoked potentials elicited by a flashing light or changing pattern on a monitor ref name osheaetal O Shea, R. P., Roeber, U., & Bach, M. 2010 . Evoked potentials Vision. In E. B. Goldstein Ed. , Encyclopedia of Perception Vol. 1, pp. 399 400, xli . Los Angeles Sage. ISBN 9781412940818 ref Auditory system auditory evoked po ... more details
T wave alternans TWA is a periodic beat to beat variation in the amplitude or shape of the T wave in an electrocardiogram ECG . Image SinusRhythmLabels.svg 300px right thumb T wave of ECG TWA was first described in 1908. At that time, only large variations macroscopic TWA could be detected. Those large TWAs were associated with increased susceptibility to lethal ventricular tachyarrhythmias . Most modern references to TWA refer to microvolt T wave alternans MTWA , a non invasive heart test that can identify patients who are at increased risk of sudden cardiac death ref Chow T, Saghir S, Bartone C, Goebel M, Schneider J, Booth T, Chan PS. Usefulness of microvolt T wave alternans on predicting outcome in patients with ischemic cardiomyopathy with and without defibrillators.Am J Cardiol. 2007 Aug 15 100 4 598 604. Epub 2007 Jun 28. ref ref Bloomfield DM, Bigger JT, Steinman RC, Namerow PB, Parides MK, Curtis AB, Kaufman ES, Davidenko JM, Shinn TS, Fontaine JM. Microvolt T wave alternans and the risk of death or sustained ventricular arrhythmias in patients with left ventricular dysfunction. J Am Coll Cardiol. 2006 January 17 47 2 456 63. Epub 2005 December 15. ref . It is most often used in patients who have had myocardial infarction s heart attacks or other heart damage to see if they are at high risk of developing a potentially lethal cardiac arrhythmia . Those who are found to be at high risk would therefore benefit from the placement of a defibrillator device which can stop an arrhythmia and save the patient s life. The TWA test uses an electrocardiogram ECG measurement of the heart s electrical conduction. The test looks for the presence of repolarization alternans T wave alternans , which is variation in the vector geometric vector and amplitude of the T wave component of the EKG. The amount of variation is small, on the order of microvolts, so sensitive digital signal processing techniques are required to detect TWA. Microvolt T wave Alternans MTWA Microvolt T W ... more details
if they form a complete loop. The voltage created is of the order of several volt microvolts per kelvin difference. One such combination, copper constantan , has a Seebeck coefficient of 41 microvolts .... The thermopower has units of V K , though in practice it is more common to use microvolts ... more details
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