Ammeter - is a device for measuring the current in amperes.

Scale ammeters is calibrated in microamperes, milliamperes, Amps or kA - in accordance with the limits of the unit of measurement.

In order to increase the limit of measurement ammeter is provided with a shunt (for AC and DC circuits), current transformer (for AC circuits only) or magnetic amplifier (for DC circuits).

In an electrical circuit ammeter in series with that portion of the circuit, the current in which the measure. Therefore, the lower the internal resistance of Ammeter (ideally - 0), the smaller will be the impact of the device on the object under study, and the higher the measurement accuracy.

Amperemeter are divided into analog or arrow digital.

Analogue arrow or ammeters  magnetoelectric have a system consisting of a coil with a thin wire, which travels between the poles of a permanent magnet. Once the coil current flows, it will move under the influence of torque, which is proportional to the current flow. coil rotation resistance has a special spring with the elastic moment, proportional to the angle of twist. At equilibrium, these moments are, and the arrow will show the value proportional to the current going through it. To increase the measurement limits, parallel ammeter connect shunt resistor set value calculated in advance according to certain formulas.

Pros analog ammeters :

  
• it does not require a separate power supply for the issuance of the testimony, as they shall be measured using the current circuit;   
• They are quite comfortable in the derivation of the information;   
• is present on many models trimmer adjustment screw to increase measurement accuracy.

Less analog ammeters :  

• a large inertia, t. E. For the arrow deflection is required for some time.

Digital ammeters It consists of analog-to-digital converter (ADC) and converts the current flowing into digital code, which is then displayed on the LCD screen.

Pros digital ammeters :

• They are deprived of the inertia inherent in analog devices;
• the issuance of the results depends on the processor speed. The expensive digital devices it can give up to 1000 or more measurements per second.
• small size, which is very critical in the modern art.

Less digital ammeters :

• they need autonomous power source, usually a battery.

Amperemeter are distinguished for measuring AC and DC.

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