A voltmeter is an electronic instrument used to measure the difference in potential or voltage between two points in an electrical or electronic circuit. The unit of potential difference is measured in volts (V).
A basic analog voltmeter consists of a sensitive galvanometer (current meter) in series with a high resistance.
The internal resistance of the voltmeter should be high; otherwise it draws a significant current and interrupts the operation of the circuit when testing.
Analog voltmeters display their readings analogically (a needle that indicates the fraction of voltage in the circuit) and digital voltmeters display their voltage readings directly in numeral form.
Practical laboratory voltmeters have maximum ranges of 1000 to 3000 V. For their part, in most commercial voltmeters they have different scales, which are increased by powers of 10; for example: 0-1 V, 0-10 V, 0-100 V, and 0-1000 V.
Voltmeters that measure high potential differences require a lot of wires and insulators.
In the field of computing, standard laboratory voltmeters are suitable because the voltages encountered are moderate, usually between 1 V and 15 V.
Analog voltmeters are generally used to measure voltages from a fraction of a volt to a couple thousand volts.
In contrast, digital voltmeters have higher precision and are used for very small voltage measurements in laboratories and electronic devices.
History
The fundamental principles behind voltmeters were established by Danish physicist Hans Christian Oersted in the year 1820, when he discovered that an electric current in a wire produced a magnetic field around it.
The first ammeter, which is a sensitive and non-resistant voltmeter, was used by physicist André Ampère in the year 1820 to measure current.
But almost all types of voltmeters are based on models in which the indicators are embedded in moving coils.
This was developed by the French physicist Jacques-Arsene d'Arsonval in the year 1882. Since that time, his capacity for movement has increased and some modern models can measure up to 20,000 volts.
Functioning
A voltmeter is a galvanometer that has been modified to measure the potential difference between two points in a circuit or series.
A galvanometer is an instrument created by Jacques-Arsene d'Arsonval that consists of placing coiled wires in a permanent magnetic field that is then attached to a spring and a calibrated dial.
Galvanometer
A galvanometer can also be modified to become an ammeter, which is used to measure larger currents.
But when this instrument is used to measure voltage, the galvanometer turned into a voltmeter connects in parallel with the area it is measuring.
Since the voltmeter must be attached to a parallel circuit, it needs to be constructed in a way that has a high resistance.
In a circuit the current will always follow the path of least resistance. When measuring the potential difference in any part of a circuit it is important to change that part as little as possible when taking measurements.
Principle of a voltmeter
The general principle of a voltmeter is that it must be connected in parallel with the object on which the voltage is to be measured.
The parallel connection is used because a voltmeter is built to have a high resistance value.
In this way, if that high resistance is connected in series then the current flow will be almost zero; this means that the circuit has been opened.
Also, in the parallel circuit, the voltage is known to be the same, so the voltage between the voltmeter and the load is almost the same.
In theory, for an ideal voltmeter, the resistance should be at infinity so that the drawn current is zero; in this way there is no loss of power in the instrument.
But this is practically not feasible because you cannot have a material with infinite resistance.
Practical uses
Voltmeters allow you to safely measure the voltage or the difference in electrical potential between two points in a circuit, and at the same time do not change the voltage of that circuit.
The ability to measure voltage is critical in the design and handling of advanced technology, but it has other applications as well.
For example, you want to turn on a fan but when you connect and turn it on nothing happens. Although the fan may be damaged, the wall outlet may not be receiving power.
A voltmeter could be used to measure plug voltage; If it is not around 120V, then the plug might be bad.
Another use is to determine if a battery is charged or discharged. When a car does not start, you can measure the battery voltage with a voltmeter to see if the problem is there.
Voltage is used in many applications in everyday life. Power transmission lines carry power at various high voltage levels, from hundreds to thousands of volts that are greater than the 120 V of common wall outlets.
Electronic devices (such as computers) require precise voltage control but operate at only a few volts and can be sensitive to even a small voltage variation.
There are different types of voltmeters for these various applications.
Types
According to the construction principle, there are different types of voltmeters. They can mainly be classified into:
- Iron Voltmeter (MI).
- Electro-dynamometer type voltmeter.
- Induction voltmeter.
- Electrostatic voltmeter.
- Digital Voltmeter (DVM).
- Permanent Magnet Voltmeter (PMMC).
- Rectifier voltmeter.
Voltmeters that are made to measure high and dangerous voltages (such as transmission lines) have extra isolation between the test points and the user to prevent the user from being electrocuted.
Other voltmeters are made to measure low voltage levels on small objects, such as computer chips, with immense precision.
The voltmeters used in these cases can be very small and are designed to eliminate or minimize noise from potential differences that exist naturally in the environment or come from nearby electronic devices.
The most common voltmeter is a handheld device with a display and two electronic leads. These wires are connected to two points in the circuit and the voltage level is shown on the screen.
References
- What is a voltmeter? Recovered from study.com
- Definition: voltmeter. Recovered from whatis.techtarget.com
- Working principle of voltmeter and types of voltmeter. Recovered from electrical4u.com
- Voltmeter. Recovered from schools.wikia.com
- Voltmeter. Recovered from ceilingpedia.com