home · measurements · How to include an ammeter in the circuit. The principle of operation of an ammeter is to measure current. What are ammeters

How to include an ammeter in the circuit. The principle of operation of an ammeter is to measure current. What are ammeters

Ammeters are used to measure the strength of direct or alternating electric current. Graphic designation this device for electrical diagrams- a circle with the letter "A" placed inside. This measuring device determines the strength of the electric current in amperes, milliamps or microamps. The ammeter is connected in series to open the circuit.

The amount of current consumed in practice is determined by the power of the device and the voltage that it must supply.

  • The voltage applied to each element is equal to the supply voltage.
  • Why only this low power?
  • Current flows through a certain point in a circuit, voltage between two points.
  • The amount of current in a circuit is proportional to the applied voltage.
  • The currents add up.
  • IN serial circuit current is constant.
Around books and laptops.

Yes, at least in films and drawings. Heat required as a result of scattering kinetic energy conductive electrons on the unevenness and vibration of a metal network. chemical energy allows you to generate a potential difference on the electrodes of two different electrolysis materials immersed in an electrolyte to which they can react. The reaction creates a potential difference and expires until the circuit closes.

Application of ammeters

Ammeters are used in industry, telecommunications, laboratory research and in other areas of activity for measuring direct or alternating electric current in the range from units of μA to tens of kA. In this case, the value of the measured current should not exceed the maximum value of the scale of the device, taking into account the connection diagram. Depending on the measurement limit, modern ammeters are divided into:

You just pumped electrons, Baterio. All of you who are leaving - come back, losing energy on the way. Each of you is a resistor who does not speak loudly. You are a light bulb - you are a heater, no one takes the heat, so you warm up to make you shine.

You are electromagnetism - you also have your resistance, although for the most part it is an imaginary resistance. We can see if you have less stress. Please, we can start with four volts. Well, the resistance can be different. Finally, he experiences the same tension.

But since you want this current, we can measure. But it's obvious, because current is the amount of spending flowing in per unit of time, and none of you collect or keep it or get rid of it. Something is wrong with this current. At least not.

  • microammeters;
  • milliammeters;
  • ammeters;
  • kiloammeters.

When was the ammeter invented?

The first attempts to measure the strength of the electric current were carried out in early XIX century. At that time to the conductor through which flowed electricity, offered regular compass. To judge the magnitude of the electric current allowed the magnitude of the angle of deflection of the magnetic needle.

Only a voltmeter can diagnose. See what kind of fasteners he supplies me. The lamp voltage is lower than the battery voltage. Let's just put voltage on the buzzer. When connected in series, the supply voltage is equal to the sum of the voltages! Therefore, in electrical installations, most receivers are connected in parallel.

Just turn on the lamp resistor in series and it shines weaker. You can connect as we provide. The girl wakes up and looks at the books. In the proposed form, the number of questions per individual current collector is not balanced. During the tests, you should check which recipients can be exchanged on the respective schemes so that everything works and deny the authors of individual applications.

What are ammeters?

Depending on the type, ammeters are divided into devices for measuring:

Exist the following types ammeters:

  • magnetoelectric - are used to measure small values ​​of direct electric current;
  • electromagnetic - provide measurement of alternating (frequency 50 Hz) and direct current;
  • electrodynamic - measure alternating (frequency up to 200 Hz) and direct current;
  • thermoelectric - designed to measure the value of alternating electric current of high frequency;
  • ferrodynamic - are recorders and applied in automatic systems measurements.

Depending on the type of scale used, these devices are:

The dialectical definition of knowledge “from living contemplation with the help of abstract thinking to experimental search” shows that experiments and measurements are an integral part of the process of cognition of a phenomenon. In the context of the scientific and technological revolution in modern world measurements. electrical are indispensable in all industries as an important link. V production processes, in quality control of raw materials, products. intermediate and final, in the development of research in all areas.

Support for electromagnetic quantities is the most frequent exchange. energy and information exchanges; precision electrical measurement. hence the normal course of the processes involved. Understand, predict and act on environment. a person must accumulate knowledge about various objects, phenomena, processes, etc. present in nature. This knowledge can be classified. introducing the concept of size. By definition, size is a property or a common attribute of a class of objects, phenomena, processes. and so on.

  • turnouts;
  • electronic (digital).

The principle of operation of the ammeter

At the heart of the work various types ammeters lie different principles actions. The methods used for measuring electric current mainly depend on the scope of the device.

The principle of operation of a magnetoelectric ammeter is based on the fact that a constant magnetic field and an electric current flowing through the frame windings cause a torque. The flow of electric current through the device causes the movement of the arrow. The latter is directly related to the frame. Therefore, the angle of rotation of the arrow is directly proportional to the amplitude of the measured electric current.

Analog devices for measuring current. Direct measurement of electric current is carried out using signaling devices of a cluster of names associated with constructive principle. The total resistance of the circuit. The resistance of the passivated circuit is viewed from the same terminals. Magnetoelectric ammeters These devices contain a magnetoelectric device in the measurement circuit and are used only in direct current. From the moment of damping through the currents induced in the frame when moving mobile device.

The deviation of the mobile device depends on the fixed coil current number. from micro. Ferromagnetic ammeters are the most reliable and widely used industrial frequency ammeters. basically. The spike resistance is chosen in such a way that most of measuring current. Ferromagnetic ammeters do not need compensation temperature errors, since they directly pass through the measuring current, the value of which depends on the impedance of use.

The design of an electrodynamic ammeter includes a fixed and a moving coil. To measure currents of small magnitude, they are connected in series, large magnitude - in parallel. The arrow is attached to the moving coil and moves as a result of the interaction between the currents flowing in the fixed and moving coils.

The dimensions of the coils and their connection scheme differ depending on the rated current of the device. The series units are built for rated currents with low rated current. They are rated. The parallel can measure currents up to 1A by connecting a moving coil to a fixed one.

Ammeters with dual sensitivity are designed with an array of two equal resistors and with the ability to connect coils and segmented sections. Heated thermocouple. between the cold chapels and the movement of the corresponding Deflection. Ammeters with very high intensity. They consist of a magnetoelectric milliammeter that measures the voltage drop across the high intensity external DC output terminals. mainly. complex design and high price extensions required abandoning this process.

The design of a thermoelectric ammeter is based on a magnetoelectric device with a contact or non-contact transducer. The latter is a conductor with a thermocouple welded to it. Passing through the converter, the electric current causes its heating, which is recorded by a thermocouple. The resulting thermal radiation affects the magnetoelectric device. Its frame deviates by an angle proportional to the value of the flowing electric current.

DC ammeters. Because of the inherent reactivity of Hall transmitters. Magnetic circuit. made of a ferromagnetic core, equipped with one or two interfaces, including elements that are sensitive to the action of a magnetic field. Ammeter with Hall sensor Since the use of weed is inconvenient. In the case of extremely large currents, the mayor is reduced to a current rod passing through a window of two cores. Measured voltage drop. They are part of an electronic multimeter based on a voltmeter or millivoltmeter connected to a current-to-voltage converter.


The operation of a digital ammeter is based on analog-to-digital conversion of the amplitude of the measured current. Passing through an analog-to-digital converter (ADC), the signal is quantized in time, and then in level. The received information is converted into digital form and displayed on the scoreboard.

Electronic devices for measuring current with low current Ammeters and milliammeters of electronic direct current. They are not a separate category of the device. each of which has a large double nozzle, are connected in differential rows and are powered by an auxiliary AC source through the rectifier ammeter. proportional to the current and the scale of the device, are calibrated in the appropriate units. In principle, electrometric devices measure very small voltages generated by high impedance sources.


How to calculate the shunt for an ammeter?

In cases where it is required to measure an electric current that exceeds the maximum value of the ammeter scale, a shunt must be used. Its resistance is calculated using the following formula:

Rsh \u003d (Ra * Ia) / (Ish-Ia)

Wherein:

Such small currents can be measured using picoammeters. corresponding rated currents and measuring the voltage drop created by the current with a digital voltmeter. The advantage of using digital voltmeters to measure currents from the voltage drop created across calibrated resistors is the ease of implementation and the use of simple digital voltmeters. Digital ammeters This is done using the ammeter function that is provided by digital multimeters.

In this regard, special amplifiers are used in the design of electrometric instruments. These are, in essence, electrometric millivoltmeters, which have as individual element electrometric amplifier. Which performs the detection function and is respected. in general. the current depends on the amplitude of the alternative voltage. an amplifier having in its output circuit a device with a permanent magnet and a moving coil, which measures the average anode current. Voltmeters of this type are compiled.

  • Rsh - the desired resistance of the shunt (in Ohms);
  • Ra is the internal resistance of the ammeter (in Ohms);
  • Ia - the maximum current value measured by an ammeter (in Amperes);
  • Ish - approximate value of the measured current (in Amperes).

Ammeter internal resistance

For correct operation, the value internal resistance ammeter should be in order less value circuit resistance. In some cases, this information is not available. Then you should measure the internal resistance of the ammeter used. To do this, a load resistance and an ammeter are connected in series to the power source, and a sensitive voltmeter is connected in parallel with the latter. After the circuit is turned on, instrument readings are taken. The value of the internal resistance of the ammeter is determined as the ratio of the readings of a sensitive voltmeter and an ammeter.

In addition to these current types of electronic voltmeters, there are special types. Diode Voltmeters Diode voltmeters are divided into series diode voltmeters and diode voltmeters. Also, electronic voltmeters can be classified by the use of semiconductor tubes or devices, or by the type of detection used. On the voltmeter series B. in the first place.

Electronic voltmeters can be classified. distinguish between analog voltmeters and digital voltmeters. So. voltmeters with a logarithmic scale and inverted triode voltmeters. voltmeters in the bridge. Abstract-free. where gain precedes detection. The device can be calibrated directly in voltage. which is schematic only electronic millivoltmeters. To get this one. which consists of a cathode repeater made of a less sensitive indicator device. This requires the use of a very sensitive resistance series measuring device. detection group uses as much resistance as possible.

It's no secret that the ammeter is special device, designed to measure the strength of electric current. Any measuring instruments help to check not only the accuracy and correctness of scientific conclusions, but also with the help of them the necessary control and management of certain technological processes. And the ammeter is no exception.

The use of a very sensitive device is very expensive and can be avoided by connecting a voltmeter without a voltmeter to the detector diode. the current passing through the resistance is very small. Electronic voltmeter with detector diode and DC amplifier.

One of the conditions that an electronic voltmeter must satisfy is the highest input resistance. The DC device in the anode circuit can measure the increase in the anode current. A typical circuit of such a voltmeter is shown in Fig. Anode detecting voltmeters Anode detecting voltmeters consist of a triode that measures the voltage of a signal applied to the grid. The corresponding features are shown in Fig. device indication is proportional to the effective value of the applied signal.

For the first time, the action of an electric current on a magnetic needle was discovered by the French scientist Ampère. He managed to establish a certain rule for exact definition the direction of the magnetic field on the magnetic needle. Now this rule is called - Ampère's rule. It was in honor of this famous physicist, a member of the Paris Academy of Sciences and an honorary member of the St. Petersburg Academy of Sciences, that the ammeter was later named.

A fixed negation is chosen. The reading is proportional to the average value of the positive alternation. On voltmeters with anode detection. application of a signal at the input causes capacitor C to be charged at a voltage equal to the peak applied voltage operating in class B, having a corresponding negative grid. the phase between fundamental and third harmonics does not change the indication. These voltmeters can be thought of as consisting of a diode voltmeter. It is mentioned in this case.

In this case. for large signals. Thus, as shown in the study of the voltmeter. Voltmeter with grid detection Schematic diagrams voltmeters on the grid are shown in fig. Plus communicates with the anode battery. the initial anode current is compensated by an auxiliary battery. vice versa. On voltmeters with grid detection. The voltage that occurs diagonally across the terminal bridge depends on the voltage applied to the grid. If no signal is given. Measure only changes in the anode current. both on the grid and on the voltmeter of the anode detector.

Types of ammeters

Today, there are several types of ammeters. Consider specifications The main of these devices are:

1. Magnetoelectric ammeters. Such ammeters are based precisely on the interaction of a moving coil and magnetic fields. permanent magnet. This device certainly has both its pros and cons. Positive sides magnetoelectric ammeter are that it is characterized by a very high sensitivity and very low power consumption. The uniform scale of the device also cannot but serve as a big plus for the main characteristics of this ammeter. But there are also negative sides: a very complex device in its essence (due to the presence of a moving coil) and operation only on direct current, which of course is not a universal device.

2. Electromagnetic ammeters. This ammeter is a special mechanism with a fixed coil through which an electric current flows, and there are also special cores - one or more installed directly on the axis. The disadvantages of such a device are low sensitivity (in contrast to the magnetoelectric ammeter), as well as low measurement accuracy. Advantages - work both at constant and at alternating current, are very simple in their device.

3. Electrodynamic ammeters. Such devices are based on the interaction of magnetic fields of currents that flow through the moving and fixed coils. These ammeters mainly use parallel and series connection of these coils. The main disadvantage of such measuring instruments is a very strong reaction to third-party magnetic fields, so their use as measuring instruments is not desirable.

4. Ferrodynamic ammeters. These are the devices that are worthy of respect. They are almost not exposed to external magnetic fields and have a fairly high strength. The ferrodynamic ammeter consists of a closed magnetic circuit made of ferromagnetic material, a central core, and a fixed coil. They are mainly used in the field of security and defense due to their high measurement accuracy.

Digital ammeter

Scientific and technological progress does not stand still, therefore, digital ammeters are gaining the greatest popularity at the present stage. Firstly, such a device is very compact and lightweight, which of course simplifies its use. There are no mechanical moving parts, as a result - it can be used in conditions in which the pointer device will not show an accurate measurement result (strong vibration or shaking). Minimal sensitivity to shock - you can not be afraid to place the device close to other mechanisms that can damage it. Another undoubted advantage of a digital ammeter is its use both in horizontal and in vertical position. These digital ammeters include shield ammeters. It is also worth mentioning that the information provided in in electronic format makes it possible to trace changes in values ​​even in automatic mode in the absence of an operator. And, of course, the main plus is the accuracy of the readings. The error of any measurements is only hundredths of a percent, in contrast to pointer instruments, the error of which sometimes reaches more than one percent. The effect of temperature and atmospheric pressure also plays no role in obtaining required measurements, either basement or measurement on outdoors. Therefore, we can say that the digital ammeter occupies a leading position among other measuring instruments of this type.

Rules for connecting an ammeter

Exist certain rules connecting an ammeter to the device, thanks to which accurate and correct current measurements can be made. First, you need to select the required shunt, the current limit of which will be an order of magnitude lower than the measured current. Now, you need to attach the shunts to the ammeter using special nuts on the ammeter.

Secondly, it is mandatory to de-energize the measured device by breaking the power circuit. Then you need to include an ammeter in the circuit with a shunt. Do not forget that polarity is extremely important. After all this, you can connect the power and read the necessary readings on the ammeter.

Application of ammeters

The scope of such a device as an ammeter is quite extensive. For example, they are widely used in industrial enterprises associated with the production of electrical and thermal energy. Undoubtedly, every physical laboratory is simply obliged to have such measuring instruments for accurate readings. Construction, science and industry, the automotive industry - everywhere ammeters have found their fairly wide application. Even ordinary motorists try to have this device available in order to always be able to identify the characteristics of the power supply of their car.

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