What Is a Displacement Meter?
A displacement meter is used to measure the height, thickness, width, or other dimensions of an object to be measured.
Since there are various types of displacement meters, it is necessary to select the appropriate measuring instrument according to the desired measurement accuracy, operating environment, and intended use.
As a result of the existence of many types of displacement meters, the level of technology has improved remarkably in this field.
Uses of Displacement Meters
Displacement meters are measuring instruments used mainly for dimensional measurement, such as the height/thickness/width of an object to be measured.
Specific examples of use include the following:
- Dimensional measurement of thickness, height, and width of pulleys and other gears in the gear machining process
- Dimensional inspection of thickness, height, and width of drive motor cores
- Dimensional measurement of height and width based on 3D shape measurement of semiconductor substrates
The following two methods of measurement exist:
- Non-contact type using light, magnetic field/sound waves, etc.
- Contact type that measures by directly touching the object
Principle of Displacement Meters
There are four major types of weighing methods used in powder weighing machines.
- Weight Loss Weight Control Type
By measuring the weight of the material in the weighing cup, feedback control is performed to control the feeder speed to approach the set value. - Volume Control Type
This is a method in which various feeders are operated at a constant rotation speed to maintain a constant feed rate.
To stabilize the accuracy of the feed rate, it is important to keep the storage volume in the storage tank constant. - Belt Type
This method detects the weight on the belt and the belt speed, and controls the belt speed with feedback control. - Hopper Type
Material is fed into the hopper after installing a separate mechanism called a feeding device, and the feeding operation is stopped when the set weight is reached.
With the recent shift to the IoT in conjunction with the spread of 5G (5G) technology, the addition of functions linked to various communication devices has also been attracting attention in recent years.
Contact-Type Displacement Meter
A contact-type displacement meter consists of a displacement meter body and a movable part, and measures the distance moved by the movable part.
Most displacement meters are equipped with an indicator to display the distance. The display meter must be selected to match the specifications of the displacement meter. Some displacement transducers come with a display, which is called a dial gauge, digital dial gauge, or other brand name, depending on the manufacturer.
There are three main types of contact-type displacement meters:
- Linear gauges, which have a measuring section that extends and retracts from the main body to measure relatively short distances.
- A type in which the measuring section slides on a rail and can measure longer distances than the above type
- a wire encoder, in which a retractable wire extends from the main unit.
In all types, the distance that can be measured is limited to the movable range of the measuring section. The measurement distance will increase in the order of 1, 2, and 3 above, and the accuracy will increase in the order of 3, 2, and 1 above.
Non-Contact Displacement Meter
In contrast to contact-type displacement sensors, there are non-contact sensors that have no moving parts.
Laser displacement meters, over-current type, and capacitance type are typical non-contact measurement methods. Among these, laser displacement meters are often used. Some laser displacement meters are capable of measuring not only vertical and horizontal movement but also depth.
The advantage of the non-contact type is that the part to be measured does not become a resistance when it moves. However, each type is often affected by the environment in which it is used. For example, the correct distance cannot be measured where there are gases or droplets that obstruct light, or where electrical noise is generated.
In recent years, a camera has been used to take pictures of the measurement area and measure the distance from the images.
Analog Type Displacement Meter
This type of displacement meter is a capacitive displacement sensor. In contrast to a digital indicator, a dial gauge with a scale plate is sometimes called a dial gauge.