Voltmeters, ammeters, resistance meters, and VU meters (volume unit meters) are often used as electromagnetic pointer meters because electromagnetic meters have some advantages for measuring electrical quantities, including the following:
1.Sensitivity: Electromagnetic meters are very sensitive to changes in current and voltage. They use the magnetic field force generated when an electric current passes through a conductor to drive the motion of the pointer. This allows them to respond to small changes in current or voltage and provide relatively accurate readings on the meter scale.
2.Linear Response: Electromagnetic meters typically have a linear current-pointer deflection relationship. This means that within the measurement range, the movement of the pointer is directly proportional to the change in current or voltage. This linear response makes the meter's readings easier to interpret and understand.
3.Simple Construction: The construction of an electromagnetic meter is relatively simple, consisting of a magnetic field and a conductor. This makes them less costly and easy to manufacture. The simple construction also makes these meters more reliable, as they have fewer wearing parts.
4.Suitable for both AC and DC: Electromagnetic meters can often be used to measure both AC and DC currents because they respond to changing currents. This allows them to function in a variety of circuits.
5.Reliability: Electromagnetic meters are generally relatively stable and reliable. They are designed so that they are stable against some transient current or voltage fluctuations.
Overall, electromagnetic pointer meters are widely used in electrical measuring instruments due to their sensitivity, linear response, simple construction, and reliability. However, for some high-precision or special applications, there are also other types of meters, such as digital meters, that are used to provide greater accuracy and functionality.
These instruments share an electromagnetic structure because they all operate according to Ohm's and Faraday's laws in nature. These laws indicate the magnetic field produced when an electric current passes through a conductor and the effect of the magnetic field on the electric current. Based on these principles, electromagnetic pointer meters use the magnetic field force generated by an electric current through a conductor to drive the movement of the pointer.
Specifically, the structure shared by these meters includes the following key components:
1.Coil: The meter contains a coil or solenoid inside it, commonly known as an electromagnetic coil. When an electric current is passed through the coil, it creates a magnetic field around it.
2.Magnet: Usually a permanent magnet or another coil is set around the coil to generate a static magnetic field. This magnetic field interacts with the magnetic field generated by the passage of an electric current through the coil, resulting in a force within the operating area of the meter.
3.Pointer mechanism: The meter contains a pointer mechanism inside, usually connected to the pointer by a slender bearing. When the magnetic field force acts on the pointer mechanism, it causes the pointer to move, which indicates the magnitude of the current or voltage.
4.Dial: Gauges usually have a dial that indicates the reading of current or voltage. The pointer moves on the dial, allowing the user to read the value of the current or voltage.
This electromagnetic-based structure enables accurate measurements and reliability in a wide range of environmental and circuit conditions. Therefore, whether it is a voltmeter, an ammeter, a resistance meter, or a VU meter, they can all take advantage of this common structure to achieve their measurement functions.
Electromagnetic meters are often designed with the pointer rebounding to the zero position while avoiding out-of-range and motor-like rotation. This is mainly achieved through the structure and working principle of the instrument.
In electromagnetic instruments, the key to the pointer rebounding to the zero position and not exceeding the range is to design a suitable mechanical limit and mechanism. Here are some common methods:
1.Spring mechanism: The pointer of the meter usually has a spring attached to it, which causes the pointer to rebound to the zero position after being subjected to an external force. The spring is designed in such a way that it can move the hand when it is subjected to electromagnetic forces within the normal range, but when the current or voltage disappears, the spring can return the hand to zero.
2.Mechanical limiters: Meters are often designed with mechanical stoppers to ensure that the pointer does not exceed the range. These stoppers provide resistance when the pointer approaches the upper or lower limit of the range, preventing the pointer from moving further. This design protects the meter from damage and ensures that the indicator is moving within the proper range.
3.Electromagnetic Reaction Force: Sometimes, the electromagnetic reaction force is used in the meter to control the position of the pointer. When the current or voltage disappears, the current in the solenoid coil also stops, causing the magnetic field to weaken and thus reduce the force acting on the pointer. This reduced force will bring the pointer back to zero.
4.Dampers: Dampers are often used in gauges to control the speed at which the hands move, which ensures that the hands return to zero smoothly and do not rotate like an electric motor. The damper is usually achieved by liquid or gas damping, so that the movement of the pointer is damped, avoiding rapid rotation or oscillation.
In summary, electromagnetic instruments use suitable structures and mechanisms such as spring mechanisms, mechanical limiters, electromagnetic reaction forces, and dampers to achieve pointer rebound to zero, while avoiding out-of-range and motor-like rotation. These designs guarantee the accuracy, reliability and safety of the instrument during use.
Although voltmeters, ammeters, resistance meters, and VU meters may look similar in appearance and structure, they each have different designs and functions, are suitable for measuring different electrical quantities, and have different operating principles and characteristics. Here are the main differences and different uses between them:
1.Voltmeter (voltmeter): A voltmeter is used to measure the voltage in a circuit and is usually connected between two endpoints of a circuit. They usually have a high resistance so that they do not affect the circuit during the measurement. The voltmeter works by using the electric field force generated by the voltage between the conductors to drive the pointer movement. They are usually connected in parallel in circuits and have very high internal resistance to minimize their interference with the circuit.
2.Ammeter (Ampere Meter): An ammeter is used to measure the current in a circuit, usually connected in series in a circuit. They usually have low resistance so that no additional resistance is introduced during the measurement. The ammeter works by using the magnetic field force generated when an electric current passes through a conductor to drive the pointer to motion. In order to prevent damage to the ammeter due to excessive current, a current limiter or fuse is usually used.
3.Resistance Meter (Ohmmeter): A resistance meter is used to measure the resistance in a circuit, usually by connecting to the element under test in the circuit to measure its resistance value. They typically have multiple ranges and have adjustable sensitivity. Resistance meters work by calculating resistance values using the relationship between the current and voltage generated by the resistor being measured.
4.VU Meter (Volume Unit Table): VU meter is used in audio devices and is usually used to measure the strength or volume level of an audio signal. They usually have a specific scale and sensitivity and are suitable for use in the field of audio engineering. A VU meter works similarly to a voltmeter, but is usually adjusted based on the characteristics of the audio signal to show the volume level more accurately.
Although these meters may be similar in appearance and construction, they are designed and functioned for different measurement tasks and electrical quantities to ensure that they can provide accurate, reliable measurements and function in specific application areas.