Using an AmmeterMohamed Bedawy
An ammeter is simply an instrument used in measuring electric current in amperes. Earlier ammeters used the earth’s magnetism to operate but today, there are ammeters that can be placed literary anyway to measure electric current in any circuit from any position.
Types of ammeters
There are a number of ammeters that are used to measure different units of currents. First is the moving iron ammeter that makes use of iron that moves when acted on an electromagnetic force of a wire with fixed coils. The moving iron ammeter will respond to both alternating currents and direct currents. The iron in the ammeter is made of a moving vane connected to a pointer, along with another vane that is fixed and surrounded by coil. When exposed to an electromagnetic force the coil creates magnetic field in the two vanes. The vanes repel and the one that moves deflects the restoring force, which is provided by the helical springs.
Another type of ammeter is the digital type. This kind is designed to use a converter that converts current from the analog format to a digital form thus is used in measuring voltage on a shunt resistor and read the current on the shunt.
The hot wire ammeter allows current to pass through wires, which then expands as the wires heat. The major disadvantage of using hot wire ammeters is that, they take a lot of time to respond and they have low accuracy. The hot wire ammeters were commonly used to measure the current in radio frequency.
Pico ammeters are used in measuring very low electric current especially from a range of picoampere to milliampere. The use of pico ammeters comes in handy when the current being measured is way below the theoretical sensitivity limits of other current measuring instruments like the multimeters. The majority of pico ammeters come with several measurement ranges and they use a measuring technique referred to as the virtual short. For this reason, the use of pico ammeters involves switching between so that to ensure coverage of several measurement decades. There are other pico ammeters that use current sink and log compression methods to read the current and time.
The use of ammeters
In many cases, the use of ammeters and electrical multitesters involves connecting in series with current circuits to read the current. In other cases, the ammeters’ shunt resistors will be connected in series for the same current reading purpose. Either way, the current must pass through a shunt or meter. To measure small currents, ammeters with Westin type of movements are used. For high currents, resistors usually referred to as shunts are placed in parallel patterns with the measuring meter. Almost all the current will then flow through the shunts with very little flowing through the meter. This in turn allows the meter to give measurements of large currents.
For measuring current in industrial and scientific equipment, the zero center ammeters are used. To operate the zero center ammeters, the ammeters are placed with a battery in series. This way, the charging battery deflects the measuring needle aside usually the right side. Discharging the battery will deflect to the opposite side. To read more about ammeters and multimeters follow onto the next page.
BY by GAHZLY