The rectified current from the detector still had radio frequency pulses from the carrier in it, which did not pass well through the high inductance of the earphones.

Later known as the Fleming valve, it could be used as a rectifier of alternating current and as a radio wave detector.

The simplest form of a metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field.

Usually several layers of alternating materials or composites are used to collect enough transition radiation photons for an adequate measurement — for example, one layer of inert material followed by one layer of detector ( e. g. microstrip gas chamber ), and so on.

The germanium is processed to form a p-i-n ( positive-intrinsic-negative ) diode, and when cooled to ~ 77 K by liquid nitrogen to reduce dark current and detector noise, produces a signal which is proportional to the photon energy of the incoming radiation.

The gyrating spins then induce a periodic current in a detector coil.

To make the most efficient use of the detector, the tube current should be reduced to keep multi-photon events ( before discrimination ) at a reasonable level, e. g. 5 – 20 %.

Plot of variation of ion pair current against applied voltage for a wire cylinder gaseous radiation detector.

This constantly changing field induces an electrical current in the second coil, and this output current is measured by a detector.

Heat causes electrons to move around and distort the current in the fMRI detector, producing thermal noise.

With the American digital television transition making most existing portable televisions obsolete and unusable and the current infant and development stage of mobile digital television, along with the need to provide a public service to their viewers and encourage the use of the system, many American television station weather operations cooperate with radio manufacturers and local retail outlets to offer weather radios at discounted pricing to viewers ( especially in active tornado areas ), where the service is often marketed as an essential warning device on par with a smoke detector for home fires.

Alpha radiation, as opposed to beta and gamma, is used for two additional reasons: Alpha particles have high ionization, so sufficient air particles will be ionized for the current to exist, and they have low penetrative power, meaning they will be stopped by the plastic of the smoke detector or the air.

This is because the regenerative detector has less gain with stronger signals, and because the stronger signals cause the tube or transistor to operate on a different section of its amplification curve ( i. e. grid V vs. plate V for tubes ; gate V vs drain V for FET's, and base current vs. collector current for BJT's ).

A bang-bang charge pump phase detector supplies current pulses with fixed total charge, either positive or negative, to the capacitor acting as an integrator.

For each detector there is a predictor trying to predict its current value from the values of neighboring detectors, while each detector is simultaneously trying to become as unpredictable as possible.

A cord set may include accessories such as fuses for overcurrent protection, a pilot lamp to indicate voltage is present, or a leakage current detector.

The output from the detector is an electric current whose magnitude is a measure of the brightness of the corresponding area of the image.

The detector circuit maintains a constant current between the two detector electrodes during titration.

and former Edison employee ) realized that the Edison effect could be used as a precision radio detector.

The crystal detector in these early crystal radio sets consisted of an adjustable wire point-contact ( the so-called " cat's whisker "), which could be manually moved over the face of the crystal in order to obtain optimum signal.

When inserted together with a galvanometer, into a tuned electrical circuit, it could be used as a very sensitive rectifying detector of high frequency wireless currents, known as radio waves.

He built a high frequency oscillator to measure the dielectric constant of gases with high precision ; Ioffe then urged him to look for other applications using this method, and shortly made the first motion detector for use as a " radio watchman ".

* 1895 – In Saint Petersburg, Russian scientist Alexander Stepanovich Popov demonstrates to the Russian Physical and Chemical Society his invention, the Popov lightning detector — a primitive radio receiver.

Point-contact microwave detector rectifiers made of lead sulfide were used by Jagadish Chandra Bose in 1904 ; the cat's-whisker detector using natural galena or other materials became a common device in the development of radio.

The point-contact crystal detector became vital for microwave radio systems, since available vacuum tube devices could not serve as detectors above about 4000 MHz ; advanced radar systems relied on the fast response of crystal detectors.

A " heterodyne " refers to a beat or " difference " frequency produced when two or more radio frequency carrier waves are fed to a detector.

Alexander Stepanovich Popov demonstrated to the public his wireless radio receiver, which was also used as a lightning detector, on May 7, 1895.

Lee De Forest's 1906 " audion " was also developed as a radio detector, and soon led to the development of the triode tube.

The tube was relatively immune to vibration, and thus vastly superior on shipboard duty, particularly for navy ships with the shock of weapon fire commonly knocking the sensitive but delicate galena off its sensitive point ( the tube was in general no more sensitive a radio detector, but was adjustment free ).

This kind of device would later be developed to become the first practical radio detector.

Hertz ’ s setup for a source and detector of radio waves ( then called Hertzian waves in his honor ) was the first intentional and unequivocal transmission and reception of radio waves through free space.

He soon found that with higher quality crystals their finicky behaviour went away, but so did their ability to operate as a radio detector.

The success of radio astronomy during the 1950s and 1960s, combined with the improvement of infrared detector technology, prompted more astronomers to take notice, and infrared astronomy became well established as a subfield of astronomy.

Early radio receivers, called crystal radios, used a " cat's whisker " of fine wire pressing on a crystal of galena ( lead sulfide ) to serve as a point-contact rectifier or " crystal detector ".

Since the early days of radio when all transmissions were in Morse Code, a demodulator has also been called a detector.

The spacecraft contained radio equipment, a tracking transmitter, a telemetry system, five different sets of scientific devices for studying interplanetary space ( including a magnetometer, geiger counter, scintillation counter, and micrometeorite detector ), and other equipment.

His initial success came from a barretter detector, which was followed by the electrolytic detector that consisted of a fine wire dipped in nitric acid, and for the next few years this later device would set the standard for sensitivity in radio reception.

* Audion receiver, a type of radio receiver that was originally designed to use the Audion signal detector

The earliest crystal radio receivers used a crystal diode detector with no amplification.

For reception, a local oscillator will typically restore the suppressed carrier so the signal can be demodulated with a product detector.

The brightness of the signal depends on the number of secondary electrons reaching the detector.

Due to the limited size of the SNO detector in comparison with Super-K the low cosmic ray neutrino signal is not statistically significant at neutrino energies below 1 GeV.

To recover the original signal from the IF SSB signal, the single sideband must be frequency-shifted down to its original range of baseband frequencies, by using a product detector which mixes it with the output of a beat frequency oscillator ( BFO ).

* Clock signal generator to synchronize the pattern generator and the error detector

The same phase of the input signal is also applied to both phase detectors and the output of each phase detector is passed through a low-pass filter.

Damped wave signals were amplitude modulated at an audio frequency by the sparks, and a simple detector would produce an audible signal in the headphones.

This IF is amplified and filtered, before being applied to a detector which extracts the audio signal, which is sent to the loudspeaker.

For example, a detector with an NEP of can detect a signal power of one picowatt with a signal-to-noise ratio ( SNR ) of one after one half second of averaging.

If the NEP refers to the signal power absorbed in the detector, it is known as the electrical NEP.

If instead it refers to the signal power incident on the detector system, it is called the optical NEP.

The signal from the phase detector is used to control the oscillator in a feedback loop.

where is the quantum efficiency ( the conversion efficiency of photons to electrons ) of the detector for a given wavelength, is the electron charge, is the frequency of the optical signal, and is Planck's constant.

Since the MRI signal drops off as the square of the magnetic field, a SQUID is used as the detector because of its extreme sensitivity.

The ions are separated on the basis of their mass-to-charge ratio and a detector receives an ion signal proportional to the concentration.

At the receiver, a simple detector recovers the desired modulation signal from the carrier.

Small errors in the detector process can greatly affect the pitch of the received signal, so single side band is not usual for music or general broadcast.

For example, for a signal modulated with a linear modulation, like AM ( Amplitude Modulation ), we can use a synchronous detector.

The product detector multiplies the incoming signal by the signal of a local oscillator with the same frequency and phase as the carrier of the incoming signal.

For example, the signal can be passed through an envelope detector ( a diode rectifier and a low-pass filter ).