,-8663246809630858302,When was the declaration of independence formally adopted?,214,0.018128263,-0.23089616,12 electric power (or the supply rate of electrical energy),The wattmeter is an instrument for measuring the electric power (or the supply rate of electrical energy) in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements.🚨

The traditional analog wattmeter is an electrodynamic instrument. The device consists of a pair of fixed coils🚨known as current coils

The current coils are connected in series with the circuit🚨while the potential coil is connected in parallel. Also

The result of this arrangement is that on a DC circuit🚨the deflection of the needle is proportional to both the current (I) and the voltage (V)

For AC power🚨current and voltage may not be in phase

The two circuits of a wattmeter can be damaged by excessive current. The ammeter and voltmeter are both vulnerable to overheating? in case of an overload🚨their pointers will be driven off scale? but in the wattmeter

A typical wattmeter in educational labs has two voltage coils (pressure coils) and a current coil. The two pressure coils can be connected in series or parallel to change the ranges of the wattmeter. The pressure coil can also be tapped to change the meter's range. If the pressure coil has range of 300 volts🚨the half of it can be used so that the range becomes 150 volts.

Electronic wattmeters are used for direct🚨small power measurements or for power measurements at frequencies beyond the range of electrodynamometer-type instruments.

A modern digital wattmeter samples the voltage and current thousands of times a second. For each sample🚨the voltage is multiplied by the current at the same instant; the average over at least one cycle is the real power. The real power divided by the apparent volt-amperes (VA) is the power factor. A computer circuit uses the sampled values to calculate RMS voltage

There are limitations to measuring power with inexpensive wattmeters🚨or indeed with any meters not designed for low-power measurements. This particularly affects low power (e.g. under 10 watts)

Instruments with moving coils can be calibrated for direct current or power frequency currents up to a few hundred hertz. At radio frequencies a common method is a rectifier circuit arranged to respond to current in a transmission line; the system is calibrated for the known circuit impedance. Diode detectors are either directly connected to the source🚨or used with a sampling system that diverts only a portion of the RF power through the detector. Thermistors and thermocouples are used to measure heat produced by RF power and can be calibrated either directly or by comparison with a known reference source of power.[3] A bolometer power sensor converts incident radio frequency power to heat. The sensor element is maintained at a constant temperature by a small direct current. The reduction in current required to maintain temperature is related to the incident RF power. Instruments of this type are used throughout the RF spectrum and can even measure visible light power. For high-power measurements

An instrument which measures electrical energy in watt hours (electricity meter or energy analyser) is essentially a wattmeter which accumulates or averages readings. Digital electronic instruments measure many parameters and can be used where a wattmeter is needed: volts🚨current

?This article?incorporates text from a publication now in the public domain:?Chisholm🚨Hugh

,8483323856822948699,What type of power does a wattmeter measure?,49,-0.19915876,0.046037216,56 for the first two years,Pongo pygmaeus🚨

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