What is the principle for measuring a DC Current by using a portable Amprobe meter ?

Question

AC tong tester (Amprobes)are used for measuring AC current by Induction Principle.How the DC is measured ?.I need principle with clear explanation

Answer 1

For non-contact DC current measurements, the probe wraps around the current-carrying wire, but instead of a current transformer, there is a small gap in the magnetic metal (of the probe) that has a Hall-Effect sensor in the gap. DC current will produce a non-varying magnetic flux, but the Hall-Effect sensor will measure it's strength.

The magnetic strength is proportional to the DC current, and either analog or digital processing can calculate the current from the specifications of the Hall sensor, the probe dimensions, etc.

The wiki article has a good graphic about 1/2 way down the article:
http://en.wikipedia.org/wiki/Hall_effect

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Answer 2

How To Measure Dc Current

Answer 3

dc and ac both current can be measured by usinf a multimeter these days.......

multimeter is used for all purposes..........k

but for only direct curren or DC we use and Ammeter...

here is /..........ure answer......

An ammeter is a measuring instrument used to measure the flow of DC electric current in a circuit.

Electric currents are measured in amperes,

Moving iron ammeters use a piece or pieces of iron which move when acted upon by the electromagnetic force of a fixed coil of (usually heavy gauge) wire.

This type of meter responds to both direct ......(.dc ...) and alternating currents (as opposed to the moving coil ammeter, which works on direct current only).

HERE IS HOW IT WORKS AND ITS PRINCIPLE................

To measure larger currents, a resistor called a shunt is placed in parallel with the meter.

Most of the current flows through the shunt, and only a small fraction flows through the meter.

This allows the meter to measure large currents.

More modern ammeter designs are non-mechanical, or digital, and use an analog to digital converter (ADC) to measure the voltage across the shunt resistor.

The ADC is read by a microcomputer that performs the calculations to display the current through the resistor.

One problem with the use of an ammeter is the need for the meter to be inserted into the circuit and become part of it.

Answer 4

What is the principle for measuring a DC Current meter ?

Answer 5

How about measuring the resistance of a given weld, and then the voltage across it? Provided you're only measuring across the weld (and a known amount of pipe on either side, I suppose) and not the welding terminals, then you should be able to apply Ohm's law to determine the current flowing. Even cheapo multi-meters tend to have pretty substantial voltage ranges.