Amperemeter ammeter What is ?
Amperemeter It is a tool used to measure the amount of current that passes through a circuit.Amperemeter Are widely used in various industries such as instrumentation, laboratories, electrical workshops. In general, ammeters can be divided into two groups: digital and analog. The difference between digital and analog ammeters is how the amount of current measured by the device is displayed, with the digital model being displayed digitally on the screen and the analog model being displayed by the hand.
How it works Digital ammeters
Unlike digital voltmeters, digital ammeters on the market do not have an automatic range. Digital ammeters are actually digital voltmeters and work in such a way that first the current being measured is passed through an ohmic resistor and then the voltage drop across both ends is displayed by a measuring device. Since digital ammeters do not have an automatic range, it should be noted that for each measurement, according to the quantity being measured, the appropriate range must be selected by the selector switch located on these ammeters. Also in Digital ammeter Also, to measure the alternating current after the selector switch, the voltage is reduced by electronic rectifiers, and then after rectification at both ends of the resistors, it is applied to the voltmeter.
How analog ammeters work
This type of ammeter shows the amount of current measured by a hand moving on a calibrated screen. The rate of deviation of the ammeter hand is directly proportional to the number of electrons passing through the device. That is, it shows how much electric charge passes through it per second.
Use of ammeters Amperemeter They must be placed in a circuit so that electric currents can pass through them so that they can measure the intensity of the current. This type of connection is called a series or series connection. That is, the components of a circuit are connected to each other in a straight line (a guiding path).
types of Amperemeter
Ammeters can be divided into the following types in terms of mechanism of operation:
1- Moving coil ammeter Moving magnet
2- Moving magnet ammeter
3- Electrodynamic ammeter
4- Moving iron ammeter
5- Hot wire ammeter
6-Ammeter Hot wire Digital
1-Moving winding ammeter
Galvanometers are a type of moving coil ammeter that uses magnetic deflection, where the current passing through the coil causes the coil to move in the direction of the magnetic field. Advanced mode of this ammeter, invented by Edward Weston, which is created using a spiral spring of return force. The air distance between the iron core and the permanent magnet poles causes the deflection of the hand to be linearly proportional to the current. These ammeters have a linear hand.
Such ammeters are able to measure currents in the range of 25 microamperes to 10 mA in the case of complete deviation of the hand.
Since the magnetic field is bipolar, the ammeter hand deflects in the opposite direction of the current. Therefore, DC ammeters are sensitive to the direction of the current and are often characterized by a positive terminal, and in some cases are made in the middle of zero, which can display current in both directions. Movable winding ammeters show the average amount of AC current, so moving winding ammeters are only used to measure DC currents.
This method is also used in other measuring equipments such as voltmeter and ohmmeter. Although less commonly used in the last decade, it is the standard method for analog displays of electric cars.
2. Movable magnet ammeter The
function of moving magnet ammeters is basically the same as a moving coil, except that the coil is placed inside the ammeter and moves a permanent hand magnet. This type of ammeter is able to measure larger currents up to several tens of amps, because the coil can be made with a thicker wire and there is no need to pass current through the spring. In addition, some of these ammeters have no springs at all and generate the return force of the hand with the help of a permanent magnet.
ammeters In electrodynamic ammeters, an electric magnet is used instead of a permanent magnet to move the hand. This ammeter is able to measure AC and DC currents and also displays the value of TRMS or True RMS for AC currents.
4. Movable iron ammeters
Movable iron ammeters use a piece of iron that operates with the electromagnetic force generated by the coil. This type of ammeter works in AC and DC currents (unlike moving coil ammeters). The iron used in this ammeter consists of a moving blade connected to a hand and a fixed blade, which is surrounded by a coil. Direct currents Alternating through the coil, it induces a magnetic field in both blades, the blades repel each other and the moving blade deflects in the opposite direction of the force exerted by the spring. The deviation of this ammeter is proportional to the square of the current.
As a result, such meters normally have a nonlinear scale, but iron parts are usually modified in shape to show a linear scale in their range. Movable iron meters for AC waveforms display the effective value or RMS. Mobile iron meters were invented in 1884 by Friedrich Drexler.
5. Hot wire ammeter
In hot wire ammeters, a current passes through the wire that causes heat to be dissipated. Although these types of meters have low accuracy and slow response time, they are used to measure radio frequency currents. It also measures the effective value or RMS for AC currents
Many measuring devices, including voltmeters, use the same methods used in analog ammeters. The main mechanism of many measuring devices is based on digital voltmeters. In digital ammeter design, a shunt resistor is used to generate a voltage calibrated to the current. This voltage is then measured by a digital voltmeter. Then, using an analog-to-digital converter, the digital display is adjusted to display the current flowing through the shunt. These meters are usually adjusted to display the effective RMS values of sine waves, but in some cases are designed and adjusted to display TRMS values (by limiting the waveform).
7. Integral ammete
A wide range of measuring equipment is based on integrated ammeters. In these ammeters, current is collected during operation, so the product displays current and time, which is proportional to the energy transmitted by the current. This method can be used in the energy of meters (meter-hours) or to estimate the charge of batteries and capacitors.
Meter Tolerances Error
It should be noted that in a given circuit different ammeters show the magnitude of the current with a slight difference. This is because some of the energy flowing in the circuit is used to power the ammeter, and not all ammeters are the same. Also due to the difference in the building Amperemeter And there is a loss of energy, the intensity of the current you read on the ammeter is approximate.
The measuring device is correct if its error range is 0% of the actual size. That is, if the mains current is 100 amps, you will read about 9 to 10 amps on the ammeter.
Rose Calibration Company in Melbourne, Australia with over ten years of experience provides all calibration, maintenance, and repair services throughout Australia. If you live in Sydney, Melbourne, Adelaide, Perth, Geelong, and Brisbane, you can receive your quote in less than two hours by fill-up the form via the “Booking” link.