Advice 1: How to connect ammeter DC

Ammeter continuous current consists of a coil of the indicator and shunt - powerful resistor of small resistance. The absence of the rectifier makes the characterisation of this ammeter is close to linear.
How to connect ammeter DC
Only use the shunt supplied with ammeter. Any other will lead to a significant distortion of the testimony. This is due to the fact that magneto indicators of different brands even with the same current full deflection have different internal resistance.
Select a shunt, designed to limit the current somewhat lower than measured. For example, if it is assumed that the current in the circuit can vary in the range from 5 to 8 And use the shunt to 10 A.
Screw the indicator has two nuts. Remove each of the screws only one of them. The second, located closer to the body, do not remove, otherwise the screw will fall inside, and to repair the device it will have to open it. Then, if he had been tested, you will need to carry out this procedure again.
Put the shunt on the screws and secure them with nuts. Don't forget about the two washers that must be placed between the shunt and the second nuts each of the screws.
Unplug the device, power consumption you want to measure. Break the chain of his power, and then, observing polarity, include in the circuit an ammeter with a shunt. Pinch the wire between the washers. Turn on the power, read the testimony, and then again power off the circuit, remove the ammeter and restore the connection.
The readings and multiply by a factor specified on the shunt. If not specified, calculate the interval yourself. For example, if the current full deflection of the indicator is equal to 100 mA, and the shunt is designed for 10 And then every microampere on the scale will correspond to the 0.1 A current in the circuit.
In a pinch you can use a shunt without the designation and any magneto-electric indicator. Connect successively the subject and exemplary ammeters. Connect them to the AVR current. Gradually increasing the current from zero, achieve full deflection of the test instrument. In the exemplary ammeter find out the current in the circuit. Divide it into the number of divisions on the scale, and thus calculate the price of one division.
Do not engage the switches energized.

Advice 2 : How to choose a shunt resistor for ammeter

The sensitivity of modern dial indicators are so high that many of them are current full deflection does not exceed one hundred microamperes. In practice, it often is necessary to measure currents of hundreds of milliamperes, and even amperes. Comes to the aid of so-called shunt.
How to choose a shunt resistor for ammeter
Before you start making the shuntand it is necessary to measure the internal resistance of a dial indicator. Use ordinary tester or multimeter (either dial or digital). In this case, it is necessary that the current through the test device was not too large, otherwise the arrow may be deformed.
Now calculate the voltage that should be provided to the indicator that the arrow has deviated completely. For this, set the full deflection current in amperes and the measured resistance of the device in ohms. Then substitute them into the standard formula of Ohm's law:U=IR where U is the voltage required for full deflection, and I is the current full deflection, R is the measured resistance of the frames.Do not be surprised that calculated according to this formula, the voltage will be very small.
Now you need to calculate the resistance of the shunt. It will be so small compared to the resistance of frames that the latter can be neglected. Resistance shuntshould be such that when passing current through it, which is of the ammeter limit, the shunte fell a voltage equal to the calculated in the previous formula. Thus, this resistance may also be calculated by the standard formula of Ohm's law, but modified in the following way:R=U/I, where R is the required resistance of the shuntand, U - naprijenie full deflection of the indicator calculated by the previous formula, I is the limiting current, the measurement of which will be calculated your ammeter (if it is expressed in milliamperes, put it in pre-amps).
Correctly connect between the indicator and the shunt. Namely himself , the shunt will engage directly in the circuit, the current in which is to be measured, and indicator connect the wires to it. Thou to do the opposite, turning on an led indicator in the circuit, and a shunt connecting the wires to the indicator, the latter will explode or even burn. Think about why.
Manufacture for microammeter new scale having graduations in milliamperes or amps and the corresponding scale.
Connecting and disconnecting the implement when de-energized circuit. Observe the correct polarity. When measuring AC, use the indicator in conjunction with the detection circuit.

Advice 3 : What is the ammeter

Ammeter - instrument for measuring current in electrical circuits. According to the principle of ammeters are magnetoelectric, electromagnetic, thermoelectric, electrodynamic and others.
Ammeter AC
The device which measure the power flowing in the circuit current is called the ammeter. Because the values, which gives the device (amperage) depends on the resistance of the elements inside the ammeter, it should be very low.
The internal structure of the ammeter depends on the purpose of use, type of current and the operating principle.
There are ammeters, which react not by resistance of the conductor and emitted by the heat or magnetic waves.

Moving coil ammeters

Devices that respond to magnetic phenomena (magneto) is used to measure currents of very small values in circuits with DC. Inside them there is nothing superfluous, except for the coil connected to her pointer and scale with tick marks.

Electromagnetic ammeters

Unlike magneto, they can be applied for networks with alternating current, often in chains for industrial use with a frequency of fifty Hertz. Electromagnetic ammeter can be used for measurements in circuits with a large current.

Thermoelectric ammeters

Used for measuring AC current with high frequency. Inside the device installed a heating element (the conductor with a high resistance) thermocouple. Due to the flowing current heats the conductor, and a thermocouple records the value. Due to the heat rejected frame with the arrow at a certain angle.

Electrodynamic ammeters

Can be used not only to measure DC current, but AC. Due to the features of the device, it can be applied in such networks, where frequency is two hundred Hertz.
Electrodynamic ammeter is mainly used as a check meter to check the devices.
They react strongly to third-party magnetic fields and on overload. Because of this, as the meters are rarely used.


Very reliable devices, which have high strength and little exposed to magnetic fields that occur not in the device. Such ammeters are installed in automatic control systems as the recorders.

It so happens that the scale of the instrument is insufficient and it is necessary to increase the values that should be measured. To achieve this, use the bypass (conductor with high resistance joined in parallel with the device). For example, to set the value of one hundred amperes, and the unit is only rated for ten, then attach the shunt, whose resistance value nine times lower than that of the device.

Advice 4 : How are ammeter and voltmeter

The principles of operation of ammeter and voltmeter based on one and the same, namely, the interaction of the magnetic field with electric current, but there are a number of distinctive features, allows to measure either current or voltage.
How are ammeter and voltmeter
You will need
  • A computer with Internet, a textbook on physics.
Read a physics textbook the basic principle used in electromagnetic instrumentation. As you know, it is based on the interaction of the magnetic field of the permanent magnet with a magnetic field coil wound on a wire frame. Coil winding is placed in a constant magnetic field which is homogeneous to the same. The wire frame is able to rotate around a particular axis. Attached to the coil spring by returning the rotation of the frame and the whole coil in a certain initial position, which is set as zero. Current is supplied to the coil through brushes attached to the axis of rotation of the coil.
Think about it, what happens when the coil electric current flows. In the absence of a current magnetic field, enveloping the coil, it does not interact with it. When the ammeter included in the circuit, the turns of the winding to form a proper magnetic field, which interacts with the magnetic field of an external permanent magnet, causing rotation of the entire frame at an angle. The angle of rotation is determined by the condition of equality of the elastic force of the spring and the force of ampere, the current in the winding from the field. The fact that the rotation of the coil ampere force gradually decreases and the elastic force increases. At some point in time these forces equal in magnitude and of the ammeter stops at a certain value, which you can observe on the scale of the ammeter.
Please note that the voltmeters are working on several types of diagrams, each of which is used in different situations. However, there are classic principles that are used in almost every device that can measure voltage. To measure the voltage at any part of the chain, you need to create the same voltage on the circuit of the voltmeter. However, as we know, a parallel connection circuit of another element the current through this section becomes less, because total current divides into two components, one of which passes through the study area and the other through the connected element. Thus, the connection of the voltmeter distorts the measurement object. This leads to the fact that the resistance of the voltmeter trying to make the most large.
When current flows through the circuit of the voltmeter first, it falls by a certain tension, which you can learn by comparison, and second, the current flowing through the element of the voltmeter, can create a certain effect, say, on any magnetic element. Here are the main ways organizations measure the voltage with a voltmeter.
Is the advice useful?