Torques in the measurement mechanism of the electric measuring instrument - News - Global IC Trade Starts Here Free

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Kaixin micro test

Test probe P100-M3

Whether it is a magnetoelectric system, an electromagnetic system, an electric system, an induction system, or an electrostatic system instrument, it generally has a rotational torque, a reaction torque, and a damping torque.

(1) Torque

The measuring mechanism can generate a rotating torque for deflecting the meter under the action of the measuring, and the magnitude of the rotating torque is related to the performance of each component of the measuring mechanism. The rotating torque can be generated by electromagnetic force, electric power, electric field force or other force. The different ways or different principles of the rotational torque constitute different series of indicating instruments. For example, the magnetoelectric meter uses the electromagnetic force between the movable coil and the permanent magnet to generate torque; the electric instrument uses the movable coil and the fixed The electric power between the coils; the electrostatic instrument uses the electric field force between the movable electrode and the fixed electrode, and the like. Each measuring mechanism, which is based on which principle, consists of a fixed part and a movable part.

(2) Reaction torque

When the movable portion is deflected, a reaction torque which increases with an increase in the deflection angle can be generated, so that the deflection angle can reflect the size of the measured child. If the movable portion of the instrument is deflected under the action of the rotational moment, if there is no reaction torque Balanced, then no matter how large the measurement is, the movable part should be deflected to the final position until it can no longer be rotated. Therefore, the instrument without reaction torque can only reflect the measured or not, but can not measure the measured size. .

The direction of the reaction torque is always opposite to the rotational moment. When measured, the rotational torque of the measuring mechanism is constant, and the movable part starts to deflect under the action of this moment. As the deflection angle changes, the opposite direction acts. The moment is also changing, when the rotational torque and the reaction torque are exactly equal. At this time, the tilting part is no longer rotated due to the torque balance, and the deflection angle has a hidden value, which is achieved by using the deflection angle clamp to indicate the measured value. The purpose of the basin size.

(3) Damping torque

When the movable part is deflected, an appropriate damping torque can be generated to limit the swing, so that the movable part is stabilized in the equilibrium position as soon as possible.

After the meter is energized, its movable part is deflected. However, since the movable part has inertia, it cannot be stopped immediately when it reaches the equilibrium position, and as a result, the deflection is over the head. After the deflection is over the equilibrium position, due to the reaction torque ratio The torque is large, the total torque is changed, and the deflection speed is gradually slowed down and finally reaches zero. However, the position of the movable part is not the equilibrium position, but has exceeded the equilibrium position. Therefore, in the total Under the action of the residual torque, the movable part is reversed to the balance direction. When the movable part is turned back to the equilibrium position, it cannot be stopped immediately due to the inertia. In this way, the movable part can swing back and forth for a long time in the equilibrium position, and finally can be stabilized in the equilibrium position, so that the measurement reading cannot be obtained as soon as possible. Therefore, the damping device for generating the damping torque is usually installed in the meter. In order to absorb the swing energy, the movable part is quickly stabilized in the equilibrium position.

It should be noted that the damping torque is generated only when the movable portion is moved, and its magnitude is only related to the moving speed of the movable portion, regardless of its deflection angle. Its direction is always opposite to the moving direction of the movable portion. Therefore, the damping torque only dampens the movement of the movable part without affecting the magnitude of the deflection angle. In other words, it is the stable deflection angle of the movable part, which is only the balance between the rotational moment and the reaction torque. Determined, regardless of the damping torque.