A measuring instrument is defined as a device for determining the value or magnitude of a quantity or variable. The electrical instrument, as its name implies, is based on electrical principles for its measurement function. These days a number of measuring instruments, both analog as well as digital ones, are available for the measurement of electrical quantities like voltage, current, power energy, frequency, power factor, etc. The instruments considered in this book are analog devices in which the output or display is a continuous-time signal and bears a fixed relationship to the input. There are various types of measuring instruments which are uses for various purposes.
We discuss here some of the measuring instruments with their uses:
- An atomic clock is a clock device that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element. Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the wave frequency of television broadcasts, and in global navigation satellite systems such as GPS. The principle of operation of an atomic clock is not based on nuclear physics, but rather on atomic physics and using the microwave signal that electrons in atoms emit when they change energy levels.
- A marine chronometer is a clock that is precise and accurate enough to be used as a portable time standard; it can therefore be used to determine longitude by means of celestial navigation. When first developed in the 18th century it was a major technical achievement, as accurate knowledge of the time over a long sea voyage is necessary for navigation, lacking electronic or communications aids. The first true chronometer was the life work of one man, John Harrison, spanning 31 years of persistent experimentation and test that revolutionized naval (and later aerial) navigation enabling the Age of discovery and colonialism to accelerate.
- A gas meter is used to measure the volume of fuel gases such as natural gas and propane. Gas meters are used at residential, commercial, and industrial buildings that consume fuel gas supplied by a gas utility. Gases are more difficult to measure than liquids, as measured volumes are highly affected by temperature and pressure. Gas meters measure a defined volume, regardless of the pressurized quantity or quality of the gas flowing through the meter. Temperature, pressure and heating value compensation must be made to measure actual amount and value of gas moving through a meter. Several different designs of gas meters are in common use, depending on the volumetric flow rate of gas to be measured, the range of flows anticipated, the type of gas being measured and other factors.
There are various types of measuring instrument are available now a days. These measuring instruments are available in the market at very cost effective prices.