A multi-meter with built-in clamp is the simple way of explaining about today's digital clamp meter. The basic job of this meter is to measure energy or electrical power. A clamp measures current and also the other circuitry i.e. voltage. If any instantaneous voltage produces any thing while the current is integrated over the cycle, the result is the true power. Any comprehensive meter, as the energy analyzer, is designed to measure different types of electrical energy and its related parameters, such as phase relationship, instantaneous power, which is a function of time, distortions and also the power factor.
The clamp meter is an electrical tester that is designed by combining a voltmeter with a current meter in the shape of a clump. This type of meter has also said adieu to analog period just like any multi-meter today. Originally, the function of the device was very minimal, rather to say single purpose, but today it is a very friendly tool for different types of measurements. The accuracy of measurement, especially in some machines it require special measurements, that makes the main features of this tool. In today's scenario, they are not simple (DMM) digital Multi-meters; they have the additional responsibility of current transformation as their inbuilt caliber.
This additional feature of current transformation in this meter can measure large ac current. As an user you need to simply clap the 'jaws' of the instrument around the conductor that is carrying ac current, the current gets coupled through its jaws. The function is exactly similar to the function of a power transformer's iron core. As its secondary functional windings it gets connected across the input-shunt of the meter. A smaller current is supplied to the input unit of the meter which is generated by the ratio of the secondary windings' number vs. the primary windings' numbers that are wrapped around the core.
There are different types of current clamps with their different functions. The first one of them is the current transformer. To detail about this clamp, it is a split ring and is made of a soft iron or ferrite iron. Either both of the halves or just a single half is wounded around with wire coil to form a winding of a transformer. The conductor that works as the other winding is clamped around it. This form of transforming unit works only with pulse wave form or AC. In some cases it extends up to megahertz range. As the current is measured, primary windings is formed by the subject conductor while secondary winding is formed by the coil.
If needed, the type can be reversed so that current can be injected into the conductor. The application of injecting current is seen in the cases of EMC susceptibility testing where an interface current is induced. The injection probe used in this matter is designed exclusively for this purpose. The coil, in this mode, forms primary winding while the test conductor forms the secondary windings.
The next type is Hall Effect type. The specialty of this type is its sensitivity. The instrument can accurately measure both alternative and direct current. The versatility of this instrument is it can measure up to thousands of hertz (kilohertz) range. These types of instruments have been specially used in the high-end computerized digital multi-meters and with oscilloscopes. But recently it has made its inroads into general purposes.
The next one is Iron Vane. The functioning of this type of instrument is, the magnetic flux, positioned in the core, affects a iron vane directly, and this allows both alternative and direct current to be measured. This facility of non-sinusoidal AC waveforms gives out a real RMS value. Since it is small in its size, it can transmit power frequencies up to 100 Hz. Usually, the vane is directly fixed to a display of the clamp meter with moving pointer.
The next one is multi-conductor. According to old or traditional system a current lamp only works when it is kept around a conductor of testing circuit. In case it is kept around both the circuits, the magnetic field will cancel itself. But a modern clamp meter has many sensor coils surrounding the clamp. The modern clamps are useful in many ways. Hence, buying a clamp meter needs many specifications to be looked into. These instruments are coming with different functions, features and overall values for its price.