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# Instrumentation

## Maxwell Inductance Bridge Circuit

For measurement of inductance, the Maxwell Bridge shown in figure 1 can be employed. It is seen that the circuit of the Maxwell Bridge is simply a repeat of the series resistance-capacitance bridge, with the capacitors replaced by the inductors. Fig.1: Maxwell Bridge  A disadvantage of this bridge is that the …

## Series Resistance Capacitance Bridge Circuit

One disadvantage of simple Capacitance Bridge is that perfect balance of the bridge is obtained only when Cs and Cx are both pure capacitances (i.e. they have virtually no resistive components). In general, this occurs only with capacitors that have air or mica dielectrics. Capacitors with other types of dielectric …

## Capacitance Bridge Working Principle

AC bridges are used for measurement of inductances and capacitances. All AC bridge circuits are based on Wheatstone bridge. Figure 1(a) shows the circuit of a simple capacitance bridge. Cs is a precise standard capacitor, Cx is an unknown capacitance, and Q and P are standard resistors, one or both …

## Phase Rotation Meter | Phase Sequence Indicator

A phase rotation meter, as shown in figure 1, is a device used to determine the phase order of a three-phase electrical system. In electrical system that contains three phases, AØ, BØ, and CØ, it is important to know the order before a motor or generator is mechanically connected to …

## Digital Multimeter Working Principle

Fig.1: Digital Multimeter There are two main types of multimeters.  One of the first and oldest multimeters is the analog meter, (Figure 2) and the other, now more widely used meter is the digital multimeter (Figure 1). Fig.2: Analog Multimeter Analog Multimeter Analog meters are a multifunctional multimeter that …

## Dynamometer Type Wattmeter Working Principle | Electrodynamometer

In a dc circuit, the power supplied to a load can be determined by measuring the load voltage and current and multiplying them together: P=EI However, it is much more convenient to have an instrument that indicates power directly. The meter used for this purpose is called a wattmeter, and …

## Megohmmeter Working Principle | Megger Working Principle

A high voltage source is required to pass a measurable current through such resistances. Thus, the megger is essentially an ohmmeter with a sensitive deflection instrument and a high voltage source. As illustrated in figure (1), the voltage is usually produced by a hand-cranked generator. The generated voltage may …

## PMMC Instrument Working Principle | Permanent Magnet Moving Coil Instrument

Figure 1 shows the basic construction of a PMMC instrument. A moving-coil instrument contains principally of a permanent magnet to offer a magnetic field and a small lightweight coil pivoted within the field. A soft iron core is included between the poles of the magnet so that the coil …

## Wire Gauge Sizes | Circular mils

For comparison of the resistance and the size of one conductor with another, some convenient unit must be established. This unit is the mil-foot (mil-ft). a conductor will have this unit size if it has a diameter of one mil (0.001 inches) and is one foot long. The circular mil …

## Impedance Measurement Theory

The opposition that a circuit offers to the flow of AC is called impedance. By measuring the voltage and current in an AC circuit and utilizing the following equation $Z={}^{V}/{}_{I}$ We can obtain the magnitude of circuit impedance. However, it is often desirable to separate impedance into resistive and reactive …

## Ohmmeter Basic Concepts and Working Principle

Ohmmeter Definition An ohmmeter is an instrument used to measure the resistance. It is an instrument containing a voltage source and a meter directly calibrated in ohms. Series Ohmmeter One type of ohmmeter is the series ohmmeter, so called because the meter movement is in series with the source of …

## Digital Voltmeter Circuit and Working Principle

In digital voltmeters, input quantity is a voltage or is converted into a voltage. Normally, digital voltmeters are abbreviated as DVM. The process by which a DVM converts the analog input into digital output is known as analog to digital conversion. The basic conversion processes are the comparison and voltage …

## Digital Frequency Meter Circuit Diagram and Working Principle

The frequency of periodic electric voltage or current can be determined directly by the use of a frequency meter or indirectly through a comparison with a known frequency. One of the many frequency meters that directly indicates frequency is reed –type meter of the following figure. Fig.1: (a) Reed-Type Meter …