Frequency meter

It is common to employ microwave power monitoring by means of a dual-directional coupler in the waveguide transmission system between the power tube and the useful load. Part of the coupled signals may be used for examination with spectmm analy2ers, frequency meters, and other microwave instmmentation for special purposes. Generally, this is not necessary in a practical appHcation. Many microwave measurement techniques have been described (59,60). AvailabiHty of components, plumbing, and instmmentation is weU described in trade journals. 

They are used for botli measuring and protection purposes. As a measuring VT, they are used to feed a voltmeter, kW, kWh or a kVAr meter, a power factor, frequency meter or a synchroscope. As a protection VT they are used to feed a protective circuit, incorporating voltage sensitig protection relays. To save on cost and mounting... 

Existing voltage and frequency-meters Incoming voltage and frequency-meters Synchroscope... 

Frequenz, /. frequency crowd attendance traffic, -messer, m. frequency meter, wave-meter, ondometer. -wert, m. frequency value, frequency. 

Electric Instruments, Many and various kinds of electric instruments are used in industrial processes and in analytical and research, laboratories, including those dealing with expls and ammunition. Among such instruments may be mentioned ammeters, voltmeters, galvanometers, thermocouples, ohm meters, wattmeters, frequency meters, oscillographs, computers, etc... 

Potential or current step transients seem to be more appropriate for kinetic studies since the initial and boundary conditions of the experiment are better defined unlike linear scan or cyclic voltammetry where time and potential are convoluted. The time resolution of the EQCM is limited in this case by the measurement of the resonant frequency. There are different methods to measure the crystal resonance frequency. In the simplest approach, the Miller oscillator or similar circuit tuned to one of the crystal resonance frequencies may be used and the frequency can be measured directly with a frequency meter [18]. This simple experimental device can be easily built, but has a poor resolution which is inversely proportional to the measurement time for instance for an accuracy of 1 Hz, a gate time of 1 second is needed, and for 0.1 Hz the measurement lasts as long as 10 seconds minimum to achieve the same accuracy. An advantage of the Miller oscillator is that the crystal electrode is grounded and can be used as the working electrode with a hard ground potentiostat with no conflict between the high ac circuit and the dc electrochemical circuit. 

Modern frequency meters allow fast measurements with good resolution, i.e., 60 ms (Philips PM6654) or 100 ms (HP5384) for 0.1 Hz resolution. The ultimate resolution of the QCM is limited, however, to miliseconds by the time required in equilibrating the crystal with the deposited mass, which is determined by the operating frequency and the quality factor of the QCM [3]. 

The rotational velocity of the rotor is measured with the aid of a perforated disc that periodically interrupts a light beam during the rotation. The pulsing light beam is fed to a photodiode the electric impulses of which are fed to a digital frequency meter. The frequency of impulses... 

Figure 2. Experimental apparatus for the investigations of acoustic cavitation in a liquid metal. (1) Signal-Generator (2) Amplifier (3) Ultrasonic Generator (4) Transducer (5) Frequency meter (6) Valve voltmeter (7) Sensor of a waveguide stick (8) Recorder (9) Cavitometer (10) Potentiometer (11) Probe (12) Crucible with a melt (13) Source of ultrasound (14) Receiving stick (15) Electric furnace (16) Detector of the first bubble.

A frequency meter is used to measure frequencies but the modern frequency source usually contains either a frequency meter or some other indication of the frequency such as the button or knob settings of a synthesizer. In the absence of a meter, the frequency source can be calibrated with a second source whose frequency is known by beating the two signals together. 

As a result of the field modulation and the phase-sensitive detection, the spectrum is recorded as the first derivative of the absorption, with the x-axis synchronized to the magnetic field that is swept across the resonance. For accurate measurements of the resonance parameters it is customary to calibrate the field, either with a field meter based on proton NMR, or to use a standard sample with known g-factors and hyperfine splittings. The microwave frequency is measured with a frequency meter attached to the microwave bridge. Modem instruments are computer controlled spectra with instrument parameters are saved and stored digitally. 

Direct measurement of magnetic field and microwave frequency An absolute measurement is possible by simultaneously measuring the microwave frequency and the magnetic field at the centre of the ESR signal using the equation g = 0.0714477 Ve(MHz)/Bo(mT), where Bo is the field at the centre of the signal and v is the microwave frequency. An accurate microwave frequency meter is often standard equipment of commercial instruments, while the calibration of the magnetic field has to be checked by a field meter usually based on NMR. 

Apparatus consisting of a QCM system, which is available commercially (ANT Tech, www.anttech.com.tw) and includes a frequency meter, an oscillator, a port connected to a computer, a software to collect and display on a computer screen, a flow-injected analysis system. 

Techniques. N.M.R. spectra of atactic, isotactic and syndiotactic samples were recorded using a Jeol PS-100 instrument and a Varian 220 spectrometer, equipped with variable temperature controller and frequency meter (10). Spectra were obtained using 5-10% (W/V) solutions in CCli or 0-chlorobromo-benzene with HMDS as internal standard. 

Instrumentation pressure gauges for steam and lubricating oil, bearing temperature indicator, electrical panel instruments (voltmeter, ammeter, KW, KWH, frequency meter, etc.). Tachometer with digital remote indication, running time totaliser. 

Standard accessories should be available along with the DG Set instrumentation for engine/generator tachometer, engine temperature, indication for electrical power drawn in kilowatts, voltage, ammeter, KWH meter, frequency meter, start up batteries, and battery charger. 

The PT is the transformer designed to provide the proper voltage to the measuring instruments such as voltmeters, frequency meters, wattmeters, watt-hour meters, etc, as well as protective devices such as relays, in which the secondary voltage is proportional to the primary and phase shift with respect to it an angle dose to zero. 

J.J. Snyder An ultrahigh resolution frequency meter . Proc. 35th Ann. Freq. Control USAERADCOM May 1981. Appl. Opt. 19, 1223 (1980)... 

The difference between the two available grades of sound level meter, precision and industrial, is effectively the degree of accuracy of the measurements particularly at high and low frequency. Meters should comply with British Standards or with lEC recommendations. 

Figure 8. Diagram of the piezoelectric microbalance used for studies of high pressure adsorption 1,2-quartz resonator, 3,4-oscillator, 5-mixer-amplifier, 6- frequency meter, 7-recorder, 8-power supplier, 9-high pressure vessel, 10-manometer.

A sensor that is especially interesting and instructive is made from a quartz crystal microbalance, or QCM. This device is based on the piezoelectric characteristics of quartz. When quartz is mechanically deformed, an electrical potential difference develops across its surface. Furthermore, when a voltage is impressed across the faces of a quartz crystal, the crystal deforms., A crystal connected in an appropriate electrical circuit oscillates at a frequency that is characteristic of the mass and shape of the crystal and that is amazingly constant as long as the mass of the crystal is constant. This property of some crystalline materials is called the piezoelectric effect and forms the basis for the QCM. Moreover, the characteristic constant frequency of the quartz crystal is the basis for modern high-precision clocks, time bases, counters, timers, and frequency meters, which in turn have led to many highly accurate and precise analyTical instrumental svsiems. 

Counting is one of the most reliable forms of measurement. As discussed in Section 4R, we always count events that occur within a set of boundary conditions (time per 100 m, apples per bushel, pulses per second, revolutions per minute, etc.). In Figure 4-2. the events to be counted are the pulses from the transducer, and the boundary conditions are used to open the gale. In this case the clock lime t is the boundary condition. The counter of Figure 4-2 is shown as a frequency meter because it can measure the number of pulses per unit lime (frequency). A general frequency meter is shown in Figure 4-4a. 

K19—preheat time-delay relay Mil—oil-pressure gauge M12— water-temperature gauge M13—dc charge ammeter M21 2 3—ac ammeter M24—ac voltmeter M25—running time meter M26—frequency meter Rll,21—resistor... 

For data input in fixed cycle operation the AMI and Siemens package type 1907 shown in Fig. 28 has been designed. With this device and a few additional components a pulse counter, frequency meter, chronometer or digital voltmeter can be built. 

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