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What Is a PCB Inspection System?

A PCB is a device that inspects for problems such as misalignment, disconnection, shorts, cracks, floating parts, and soldering of components mounted on the board. This inspection is called board visual inspection.

In addition to functional testing of electronic circuit boards to ensure correct operation, board visual inspection (also called board inspection or mounting inspection) inspects whether each electronic component is mounted in the correct position without defects.

Electronic board inspection is called AOI (Automated Optical Inspection).

If there are no problems in the board visual inspection, a functional inspection is performed to ensure that the product actually works as designed.

Function testers are used for this functional inspection.

Uses of PCB Inspection Systems

Until now, board visual inspections have been performed visually by human eyes.

However, with visual inspections, the criteria for acceptance or rejection may differ depending on the subjectivity of the inspector.

In addition, the more inspection items are required, the more personnel are needed, resulting in higher labor costs.

In addition, electronic circuit boards are generally manufactured in a factory on a production line. Visual inspections have a limited processing capacity, and this limits the speed of the production line.

PCB visual inspection systems are introduced to increase efficiency and reduce costs by automating inspections that were previously performed by human labor.

Principle of PCB Inspection Systems

Since PCBs use a machine to perform what was originally done visually, it requires “eyes” to see the appearance and “brains” to judge whether it is good or bad, just like a human being.

Therefore, the PCBs consist of a camera as the “eye” and a computer equipped with image processing software as the “brain”.

The most common defect in board visual inspection is soldering defects.

The PCBs determine whether soldering is good or bad by using a straight line connecting the boundary of the solder adhesion surface and the electronic component adhesion surface as a threshold value and whether or not it exceeds this value.

Since the threshold value varies depending on the shape of the component and other factors, such as the electronic board, it is necessary to input all kinds of threshold data into the image processing software.

In recent years, to alleviate this complication, three-dimensional imaging with multiple cameras and the use of X-ray cameras have made it possible to detect defects that cannot be detected with ordinary cameras.

False Alarm Rate

The false alarm rate is one of the most important indicators for inspection equipment.

Although it is as old as 2009, here is an article describing the false alarm rate data from a survey on the current status of product inspections conducted by the Japan Institute of Electronics Packaging to Japanese manufacturers of printed circuit boards and electronic devices.

Inspection of Board Mounting by PCB Inspection Systems

Electronic boards manufactured by manufacturers can have various types of defects. For this reason, various types of PCB inspection systems are used to identify boards with defects. There are various types of board defects, the most common of which are listed below.

1. Component Defects

• Component Not Mounted: Component is not mounted in the correct position
• Component misalignment: A component is removed from the pad and mounted out of the correct position.
• Component floating: Only one side of the component is soldered and the other side stands up.

2. Solder Defects

• Disconnection: No solder is applied
• Short: Excessive amount of solder adhering to adjacent pads
• Void: A defect caused by air bubbles during soldering
• Poor wetting: Solder is clean but electrical contact is incomplete
• Solder ball: A ball-shaped lump of solder
• Bridging: Solder is connected between adjacent IC pins
• Cracks: Cracks on the surface of the solder
• Imo-solder: Solder does not bond well and the solder is bumpy like a potato

What Is AOI?

AOI stands for Automated Optical Inspection. It is an automated visual inspection in which an electronic board is photographed by a camera or other means to inspect for serious defects and quality defects. Because optical inspection is non-contact and non-destructive, it has been introduced in many board manufacturing processes. Methods used in automated optical inspection include camera-based imaging, laser reflection, and X-ray transmission.

Visual inspections used to be performed by human operators, but they are now widely used for a number of reasons, including the fact that it is no longer easy to distinguish between small, integrated boards due to the increasing integration of circuits, cost reductions and productivity increases due to labor and manpower savings, and quality value enhancement by reducing human error.

What Is a Print Inspection System

A print inspection system is a device that inspects for errors or problems in the printing of dates in manufacturing processes in the food and medical industries.

In recent years, consumers have become increasingly aware of the need for safety and security, and errors in the labeling of product expiration dates in the food and medical industries can lead to major problems. Any printing error can result in not only the loss of money and time associated with product recalls, but also the loss of customer trust.

Therefore, a print inspection system that prevents errors caused by human factors is in high demand in the manufacturing field. The introduction of a print inspection system enables stable inspections with high accuracy and consistent standards and also guarantees records through image storage.

Uses of Print Inspection Systems

Print inspection systems are often used on production lines to inspect the presence or absence of print, as well as any missing or incorrect print, on the expiration date, factory-specific symbols, lot numbers, and other items printed on products and packages.

The system can inspect the printing in areas that are difficult to identify manually or that require time for visual inspection, such as the backside of products. Images used for inspection can also be saved, which helps reduce risk by anticipating problems after shipment.

The print inspection systems can be linked with a mechanism that ejects only NG products after inspection. By interlocking with the ejection mechanism, NG products can be ejected while the line is still in operation. The main mechanisms that can be introduced include an air jet ejection mechanism from an air outlet and an arm mechanism to eject NG products with pinpoint accuracy.

Principle of Print Inspection Systems

Print inspection systems consist of a camera that captures images of the printed surface, an analyzer that inspects the captured images, a monitor that displays the results and settings, and storage for storing the images.

A fixed digital camera captures images of the printed surface as it flows from the production line. The captured images are subjected to image analysis and inspected for problems. In production, it is important not only to detect errors with high accuracy but also to avoid detecting errors excessively.

With the development of image analysis technology, there are print inspection systems with many features that can detect not only characters in the printed area but also other problems such as the presence of smudges. In addition, there are also print inspection systems available that can be linked to a printing machine, which is expected to improve inspection efficiency and further automate the process.

Other Information on Print Inspection Systems

Advantages of Print Inspection Systems

1. Reduction of Inspectors and Elimination of Errors
By installing print inspection systems, the work can be done without the inspectors’ manual labor required for print inspections. In addition, when inspections are conducted manually, inspection errors can occur. To maintain work efficiency and quality assurance for a long time, print inspection systems are very important.

2. Highly Accurate Print Inspection
Some models of print inspection devices are equipped with a printer interlocking function, which automatically synchronizes item switching, calendars, etc., eliminating omissions and errors in settings. In addition, print inspectors can identify misprints, missing prints, and missing prints with high accuracy, thereby controlling excessive error reactions and preventing unnecessary lost items, thereby ensuring reliable inspection while maintaining productivity.

3. Print Images Can Be Saved to Prevent Recurrence
By saving the inspection images of the print inspection machine, it is possible to keep an inspection history at the time of shipment. If a problem occurs after the product has been shipped, the cause of the problem cannot be identified because the date and time of the print inspection and the condition of the product at the time of shipment cannot be confirmed if the inspection images are not saved. By storing all inspection images, it is possible to investigate the cause of the problem and prevent recurrence, which has the advantage of leading to a more stable supply of food and medical products.

What Is an Image Sensor?

An image sensor is a component that converts light information into electrical signals.

Image sensors are the CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) sensors used in digital cameras and other photographic equipment.

Image sensors are the “eyes” of a machine. The number of pixels in an image sensor used in a camera refers to the total number of image sensors. Each sensor detects the intensity of light, which is quantified and processed as an electrical signal.

Uses of Image Sensors

Image sensors are mainly used in production lines for mass-produced products. For example, they are useful in production lines for automotive parts, food and medical products, electronic devices, liquid crystals, semiconductors, and plastic products.

The role of image sensors is to provide an alternative to visual inspection by the human eye. They are applied in various tasks such as quantity counting, presence/absence inspections to detect missing products, and visual inspections to identify scratches and defects.

In combination with advanced image analysis technology, they are also used for character identification (OCR: Optical Character Recognition) and 3D measurement. Image sensors are also used in automated driving systems and will continue to be essential devices in the future.

Principle of Image Sensors

The core of an image sensor is a light-sensitive semiconductor (photodiode). This semiconductor senses the intensity of light and stores it as an electrical charge. When light strikes the photosensor, electrons are produced in proportion to the intensity of the light.

The basic principle of image sensors is to use the properties of semiconductors to store electrons and quantify the amount of electrons. In image sensors, there are devices based on different principles, depending on how the electrons stored in the light-receiving element are converted into a signal. The main devices are CCD and CMOS.

In CCDs, the charge is converted to an electrical signal by means of a CCD transfer path. In CMOS, each photodetector has its own amplification circuit (amplifier). Therefore, the charge can be transferred without having to go through multiple photodetectors.

Since CMOS is driven by a single device, it has the advantages of low power consumption and high processing speed. It is also attracting attention for its lower manufacturing cost than CCD.

Other Information on Image Sensors

1. Image Sensor Size

Image sensors come in several sizes. Usually, image quality improves as sensor size increases. The reason is that the larger the sensor size, the more light it can collect.

The greater the range of light that can be captured, or dynamic range, the better the image can be captured with fewer blown-out whites and blacks. In addition, the larger the size of an image sensor with the same number of pixels, the better the image quality, because the light-receiving area per pixel (1 pixel) is larger, which also reduces noise.

2. Role of Illumination in Image Sensors

Illumination is a device that interpolates the image sensor for FA. Illumination is necessary for the image sensor to stably detect a workpiece without being affected by ambient light. The following three lighting methods are common:

Orthoreflective Method
This method illuminates the workpiece from above at an angle and captures the image reflected on the surface of the workpiece. This method makes it easy to obtain contrast between flat and uneven areas of a workpiece, such as a metal plate with uneven surfaces.

Transmission Method
This method illuminates the workpiece from the back and captures the image from the surface. The contours of workpieces with complex shapes can be imaged more accurately.

Coaxial Epi-Illumination Method
This is a method in which the optical axis of the camera is coaxial with the illumination optical axis irradiating the workpiece. The entire workpiece is illuminated evenly and shadows can be minimized.

3. Price of Image Sensor

The price of an image sensor is determined by its “field of view” and “accuracy”.

Field of View
Normally, the larger the number of pixels in an image sensor, the finer objects can be detected. The larger the number of pixels, the larger the size of the sensor and the higher the price.

In addition, processing time tends to increase because of the time required for data transfer. It is important to select a sensor that matches the tact of the system to be operated.

Accuracy
Image sensors with higher pixel counts are more accurate. Depending on the object to be detected, a monochrome sensor or a color sensor may be required, but a color camera is more expensive.

What Is an Ohmmeter?

An ohmmeter is a measuring instrument used to determine the resistance of an electrical circuit.

It is one of the indispensable measuring instruments in electronics and electrical work, and is available in a wide range of accuracy and range. They are called ohmmeters because they use Ohm’s law to measure resistance.

There are several types of ohmmeters: milliohmmeters are specialized for resistance values of mΩ or less, insulation ohmmeters are used to measure the resistance of insulators, and ground ohmmeters measure the resistance between a grounded conductor and the earth. Although simple testers are sometimes used to check the resistance of circuits, ohmmeters with high accuracy are required in development and manufacturing.

Uses of Ohmmeters

Ohmmeters are used to measure the resistance of electric circuits. The following are examples of applications of ohmmeters:

1. Fault Locating

Resistance testers are useful for locating faults in electric circuits. By measuring the resistance of each part of an electric circuit, it is possible to identify the part that is out of the normal range. This type of measuring instrument is indispensable for maintenance and security of electric circuits.

2. Circuit Design and Development of Electrical Equipment

It is also used in circuit design. When designing circuits, accurate resistance measurement of elements is necessary. Some ohmmeters have a basic accuracy of 0.02% and a resolution of 1µΩ. Such ohmmeters are used in electronic device design, manufacturing, and quality control.

They also play an important role in the development of electrical devices. Electrical equipment as a product also requires accurate resistance values, which are obtained with ohmmeters.

3. Research and Development and Education

Resistance meters are also used in the field of research and development of basic materials. Ohmmeters are used to investigate the properties of materials and circuits. They are also used in educational settings, particularly in the study of electrical and electronic engineering, to measure circuits. This enables students to understand the characteristics of circuits and how to measure resistance.

Principle of Ohmmeters

Resistance meters use Ohm’s law to measure resistance. Ohm’s law is a law that states that resistance, the ratio of current to voltage, is constant. This law can be used to determine the resistance in a circuit.

Ohmmeters contain a power supply and a measurement circuit. The measurement power supply is generally supplied by a battery or AC adapter. The measurement circuit also incorporates an ampere meter to detect the circuit current to be measured and a volt meter to measure the circuit voltage.

Most precision ohmmeters use a contact-type four-point method of measurement: two of the four wires pass a constant current through the object, while the other two act as voltmeters to measure the voltage. By measuring the voltage produced when a constant current flows, resistance can be determined from Ohm’s law.

Simple testers use the 2-terminal method, which is inexpensive and easy to construct, while the 4-terminal method can measure resistance more accurately than the 2-terminal method because it is not affected by the resistance of the measuring leads or contact resistance.

Types of Ohmmeters

Various types of ohmmeters are available depending on the application. The following are examples of ohmmeter types:

1. Analog Type Ohmmeter

Analog ohmmeters use an analog pointer to indicate the resistance value. The needle vibrates according to the current flowing in the circuit, indicating the resistance value. Although they are relatively inexpensive, it is necessary to select the appropriate range according to the resistance range of the circuit to be measured.

2. Digital Type Ohmmeter

Digital ohmmeters are resistance meters that show resistance values on a 7-segment display. They are capable of high-precision measurement and are often equipped with a function that automatically switches the range. Testers with voltage and current measurement functions are also part of digital ohmmeters.

3. Clamp Type Ohmmeter

This ohmmeter measures resistance by generating a magnetic field around the circuit with a clamp between the clamps. The advantage of this type of tester is that it can make measurements without coming into contact with the circuit to be measured. It is often used as a ground ohmmeter.

4. Ohmmeter

This ohmmeter is used to diagnose the insulation condition. Insulation resistance is measured by grounding one terminal, applying high voltage, and measuring the leakage current. Ohmmeters capable of applying a high voltage of about 1,000 VDC according to the system voltage are also available. Ohmmeters are widely used for maintenance at production sites.

What Is a DRAM Module?

DRAM module is a type of volatile storage device (memory) that uses semiconductor elements.

DRAM module is an abbreviation for Dynamic Random Access Memory and is mainly used in personal computers. Because the internal circuit has a very simple structure with a capacitor for storing electric charge and a field-effect transistor (FET), the DRAM module is suitable for large-scale integration in conjunction with the miniaturization of the FET semiconductor process.

Uses of DRAM Modules

DRAM modules are mainly used in personal computers. DRAM modules are used in PCs and industrial machinery control devices that require inexpensive, high-capacity memory because the memory part has a simple structure using capacitors and FETs (field-effect transistors) and can be manufactured at a low unit price for the memory capacity.

DRAM modules are not often used in small devices such as smartphones and mobile terminals because of their power consumption due to their structure of storing information with stored charge in a capacitor and the constant refresh process of writing and reading information to maintain the charge.

Principle of DRAM Modules

The principle of DRAM modules is that they handle a huge amount of data as a storage medium using a binary number, 1 when there is a charge stored in a capacitor in the internal circuit and 0 when there is no charge stored in the capacitor.

When writing data, the charge is accumulated in the capacitor via the FETs and the area where the voltage is high is set to 1 and the area where no charge is accumulated is set to 0. When reading data, the charge in the corresponding area is released, and the reverse operation of writing is used to identify 0s and 1s from the state of the charge stored in the capacitor. This is the mechanism for storing and expressing digital data by performing these operations countless times.

As can be seen from this mechanism, DRAM modules can only retain information while electricity is flowing because a voltage must be applied to the capacitor to accumulate an electric charge. For this reason, DRAM modules are classified as volatile memory.

Other Information on DRAM Modules

1. The Difference Between DRAM Modules and SRAM

Generally, DRAM modules and SRAM are compared when looking to increase the memory capacity of a PC.

Each has its characteristics, and SRAM is superior in terms of memory performance. The major difference is whether the memory style is dynamic or static, with DRAM modules constantly reading and writing information, while SRAM is the opposite. Although SRAM offers high-speed read/write and low power consumption, its disadvantage is that its complex internal circuitry makes it difficult to integrate on a large scale. If a small, inexpensive, large-capacity memory is needed, it is important to select an appropriate memory size from DRAM modules.

2. Differences Between DRAM Modules and Flash Memory

Flash memory is a semiconductor product with similar functions to DRAM modules. Both play different roles on a computer due to their characteristics.

DRAM modules are volatile when no power is supplied, but because of their high processing speed, it is used as the main memory of a computer to temporarily store data needed for arithmetic operations. Flash memory, on the other hand, is non-volatile and does not require a continuous supply of electric charge to retain data, so it is mainly used for long-term data storage.

Comparing the data read/write speeds of flash memory and DRAM modules, DRAM modules are faster, but DRAM modules are more expensive. Compared to magnetic tapes and HDDs, which are used for long-term data storage, flash memory has been used for storage products such as SSDs and USB memories in recent years due to its faster data read/write speed and lower price.

3. Refresh Operation of DRAM Modules

DRAM modules are a volatile device that loses its memory unless power is continuously supplied, so it must be periodically refilled with electric charge. This charge replenishment operation is called a refresh operation. This interval is called a “refresh cycle. Normally, refresh operations are performed at intervals of about 15 microseconds to 60 microseconds.

Since memory cannot be accessed during the refresh operation, it must be performed in as short a time as possible. A memory that can be refreshed in a short period is said to have higher performance. 

4. DRAM Modules Memory Capacity Trends

In the 1990s, when Japanese manufacturers were the main players, the DRAM module’s memory capacity increased by a factor of 4 with each generation, from 1 Mbit to 4 Mbit. In the 2000s, however, the increase slowed to 1Gb to 2Gb, and in the 2020s, DRAM module capacity has continued to increase by less than 16Gb.

Contributing to the trend of increasing DRAM module’s storage capacity is semiconductor FET miniaturization process technology. The most advanced process node of the semiconductor process has evolved to a few nm, and active development competition is underway among world-renowned companies and research institutes.

What Is a Nut Runner?

A nut runner is a power tool that can automatically tighten nuts.

Some models can be used for screws and bolts by changing sockets as well as nuts. Most nut runner is hand-held, but there are also fully automated models. Nut runners can set the tightening strength, thus ensuring homogeneous and highly precise tightening.

Nut runner is widely used in fastening areas where reliability is required because they enable highly accurate and reliable fastening as well as simplify the work.

Uses of the Nut Runners

Because of the homogeneity and high precision of tightening with nut runners, they are widely used in automobile parts, motorcycles, shipbuilding, and other areas where safety assurance is required. They are also often used for equipment inspections requiring more precise tightening, such as at gas stations and chemical plants, and at construction sites where steel frames of buildings and other structures are assembled.

Nut runners may also be incorporated into fully automated automatic assembly equipment. When selecting nut runners, the torque range of the nuts and bolts to be used should be checked.

Principle of Nut Runners

Nut runners can be broadly classified into two types: those driven by an electric motor and those driven by air pressure. The motor is used to rotate the torque, and the nut runners are set to automatically stop when tightening is completed.

1. Drive by Electric Motors

Since the torque and angle are electrically controlled by an electric motor, it is more accurate than a pneumatic drive, and work history and data can be kept. Cordless types are also available and have become popular in recent years.
It is important to choose an insulated or pneumatically operated nut runner if there is a risk of electric shock due to its tendency to generate heat. Also, since retightening is not possible, it is necessary to loosen the nut once when retightening it again. 

2. Pneumatic Drive

An air compressor is required, and compressed air is used to turn an air motor to control torque. The advantage is that there is no risk of electric shock, but the disadvantage is the high cost of electricity due to the use of an air compressor. This type has been used for a long time because it generates less heat than an electric motor drive and is suitable for use over a long period.

Nut Runners Structure

The electric type uses an AC servo, DC brushless, or other motor that can control the number of rotations, while the air-driven type uses an air motor driven by pneumatic pressure. The control unit is either built-in or installed separately. Their rotation is transmitted to the drive shaft via a planetary gear reducer.

Some high-performance types have a torque detection function and can control rotation by torque, while others can be equipped with an arm that detects position and posture.

Other Information on Nut Runners

1. Nut Runners and Electric Drivers

Nut runners are nut-tightening tools, hence the name, but they can also be used for screws and bolts that are fastened by rotation. The difference between electric screwdrivers and impact wrenches is that the tightening torque can be accurately controlled.

While electric screwdrivers and impact wrenches have a structure in which the shaft idles when the specified torque is reached, electric nut runners have a function in which the rotation of the motor decelerates as it approaches the specified torque value, thereby stopping the motor at the exact torque value. In recent years, electric nut runners have become the mainstream for more accurate tightening.

The nut runners perform tightening while controlling the rotation speed and torque according to the torque value at the time of tightening. Although their rotational speed is inferior to that of electric screwdrivers and impact wrenches, they feature less error in torque value after tightening and less noise during operation. 

2. Torque Control of Nut Runners

Recent nut runners monitor changes in torque and angle during tightening to determine whether tightening is good or bad, and can detect such problems as bolts being inserted at an angle, washers being forgotten, or two washers being inserted at the same time. Such data can be stored in the nut runners themselves or wirelessly transferred to a PC or other device and recorded as data during assembly.

In addition, advanced models can also detect the posture and position of the nut runners. It can determine the position of the hole to be tightened to determine if the screw or bolt being tightened matches the specified one, or it can determine the difference between screws and bolts from the screw hole position and change the tightening torque by itself.

What Is a Hydraulic Pump?

Hydraulic pumps generate mechanical energy by operating an electric motor. When a hydraulic pump is driven, oil circulates and converts mechanical energy into fluid energy. Fluid energy is sometimes referred to as hydraulic energy. This fluid energy combines the pressure and flow required by the hydraulic actuator. The pressure would only push the fluid if either of these energies were not being generated. When oil enters the hydraulic actuator, fluid energy is converted to mechanical energy. The converted mechanical energy becomes linear or rotational motion that powers the pump.

Types of hydraulic pumps include general positive displacement pumps, constant displacement pumps, and variable displacement pumps.

Uses of Hydraulic Pumps

Structural products that use hydraulic pressure use a series of operating mechanisms called hydraulic units, which vary slightly in construction type, but all of them have hydraulic pumps built in. Since hydraulic power is a combination of pressure and flow rate, doubling the pressure without changing the flow rate doubles the horsepower. Changing the flow rate by a factor of 2 without changing the pressure will also approximately double the horsepower.

In general, hydraulic pressure is used in many situations where large external power is required, especially in heavy equipment such as excavators and cranes used at construction sites. It is also often used in equipment that is small but requires large torque. For example, they are widely applied in the transportation industry represented by airplanes, ships, and automobiles.

Other pumps that utilize natural forces also exist. A specific example is the use of devices that pump water on farms. Such pumps are used in conjunction with sensors that detect water levels, as they require continuous operation. Windmills are another example. Windmills use hydraulic pumps to pump water out of the ground with the force of the wind.

How to select Hydraulic Pumps

Two types of power use fluids: pneumatic and hydraulic. Both are structured to convert a small force into a large force by applying Pascal’s principle. However, their features are somewhat different.

The pneumatic type is inexpensive and has a simple structure. It is more dependent on the environment, such as ambient temperature, and has lower responsiveness. However, if the appropriate type of hydraulic oil is selected, it can be used in all weather conditions. When large forces that cannot be achieved with the pneumatic type are required, it is advisable to select a hydraulic-type unit and appropriate hydraulic pumps to accompany it.

Principles of Hydraulic Pumps

All pumps are available in positive displacement and non-positive displacement types. Since most hydraulic systems use positive displacement pumps, the principle of positive displacement pumps is discussed here.

A positive displacement pump is divided into two parts: one filled with hydraulic fluid and the other, called a positive displacement chamber, which contains only gas. In a positive displacement pump, an intake valve draws fluid into the pump chamber and an exhaust valve discharges the fluid.

First, when an external driving force is applied to cause piston motion, a negative pressure is generated on the volume chamber side, resulting in suction pressure. This is called the expansion process.

Next, the suction process begins. When this pressure exceeds a certain value, the difference in atmospheric pressure between the hydraulic oil chamber and the oil tank to which it is connected causes the hydraulic oil to be sucked in through the intake valve. At this time, the exhaust valve is closed.

The pressure difference is reversed when the volume chamber side becomes positive pressure. This process is called the compression process.

Finally, the discharge process takes place. Oil is discharged from the exhaust valve by the force of the hydraulic oil being pushed outward. When the oil is pushed out, the intake valve closes and the exhaust valve is released.

These four processes are repeated indefinitely as one cycle to keep pumping the hydraulic oil in a constant direction.

The suction and discharge sides of the oil tank are each equipped with a check valve in one direction, so that when pressure is generated on either side, one side is pulled closed by the pressure and there is no backflow.

Structure of Hydraulic Pumps

Hydraulic systems, including hydraulic pumps, are widely used in industry because they provide large power with little power. First, the system is powered by a prime mover that boosts hydraulic oil pressure via hydraulic pumps. Next, hydraulic oil is fed to the hydraulic actuators by controlling the pressure with hydraulic valves. It is then converted into mechanical energy such as rotational motion. Among these, the hydraulic pumps are the most important equipment to ensure the necessary mechanical power by boosting the pressure of the hydraulic oil.

Hydraulic pumps are mainly divided into “gear type,” “vane type,” and “plunger type”.

Gear pumps boost hydraulic oil pressure by meshing gears in the casing.

Vane pumps have a rotor built into the vane inside the casing, which rotates the vane to raise the pressure of the hydraulic oil. These blades are called vanes.

In a plunger pump, a reciprocating piston or plunger adds pressure to the hydraulic oil to boost pressure.

Both pumps still boost the pressure of the hydraulic oil, but if a leak of hydraulic oil occurs, it contaminates the environment and is time-consuming to deal with. Sealing performance is of a high standard due to advances in technology. However, since leakage will never be zero, installed pump units must be installed inside an oil embankment, for example. In addition, transportable pump units must have good sealing to prevent leakage since the entire unit will be moved. Even if hydraulic oil should leak outside, an oil tank or similar facility can be installed to prevent oil leakage.

Power for Hydraulic Pumps

There are two types of hydraulic pumps: electric and manual. The electric type is mainly used in industry and experimental facilities, and the pump is powered by electricity. On the other hand, the manual type is powered by the force applied by a person. Mainly, the manual type uses a piston in the path to generate power. Hydraulic fluid is pumped into the piston by operating the handle with human power. The piston, under the pressure of the hydraulic fluid, provides power to the outside world. The advantage of using a manual type is that the mechanism is simple and easy to maintain. In addition, the slow transmission of force when transmitting power allows for fine adjustments. This results in risk assessment.

A commonly used hydraulic jack is the hydraulic jack used to change a car tire. This is a manually operated hydraulic pump that transmits power by sending hydraulic oil to the power to lift the car.

The electric type is mostly used in industrial applications, as this pump is used when a greater workload needs to be given. The electric type is more complex in structure than the manual type, so a wide variety of types are prepared according to the performance required. However, pumps with simple structures are also manufactured, making them inexpensive and easy to install. They can also be used on land or water where large amounts of power are required.

Thus, the electric and manual types differ not only in the power source but also in the scale of the application for which they are used.

What Is a Torque Meter?

A torque meter is a device that measures the rotational force applied to a shaft, called torque.

Using the elastic force of a spring or a sensor, it is possible to obtain the force in the direction of rotation as a numerical value. Analog torque meters can display numerical values by themselves, while digital torque meters require a numerical value display and a power supply to operate.

Torque is classified into static torque and dynamic torque, and it is necessary to decide in advance which of the two needs to be measured depending on the purpose of measurement. In recent years, models that can measure both types of torque have become widely used.

Uses of Torque Meters

Torque meters are used to apply a rotational force to a shaft and measure the force in the rotational direction numerically. They are used to measure and control the actual numerical values of the tightening force of screws, the torque to open and close container caps, and the torsional rigidity of shafts, beams, and other structural members.

In recent years, many of them can simultaneously measure not only torque but also strain and shaft rotation speed. Measuring and controlling torque is a very important item to ensure not only proper operation and maintenance of equipment but also safety in the event of life or failure.

Principles of Torque Meters

The simplest principle of torque meters is to rotate torque meters directly connected to a shaft and display the rotational force as a numerical value by the repulsive force of a spring or the like. In recent years, various types of torque meters have become available, including those that use a sensor to measure the strain during rotation as a torsional angle of the shaft to calculate torque, and those that measure torque indirectly as well as directly.

A rotating shaft always has both a motor or other power source to transmit rotation and a turbine or other mechanism to utilize rotation, so a mechanical type torque meter with scale at the end of the shaft requires either mechanism to be removed to use it.

There are also torque meters that are inserted in the middle of the shaft, but the shaft is removed in the same way to install the torque meters. Therefore, mounting and dismounting must be considered when installing torque meters.

Other Information on Torque Meters

1. Motor Testing With a Torque Meters

Torque meters are available in non-rotating strain gauge types, rotating magnetostrictive types, and strain gauge types. The rotary-type torque meters are used for experimental and research purposes and quality control of products. Torque is often heard in the tightening of tire nuts, and the specified torque varies depending on the type of nut.

Torque is also important in motors. Motors are used in many other places besides trains and automobiles, such as pumps, compressors, and elevators.

In motor manufacturing, torque meters are used to confirm that the final torque value is the desired one. Generally, after a motor is manufactured, a load is applied to the motor in a motor testing machine, and measurement is made with sensor-type torque meters.

2. How to Use a Torque Meters

There are two types of torque meters: non-rotating type and rotating type.

Non-Rotating Type
The non-rotating type has a gauge attached to the device to be measured, and the gauge displays the value of the torque applied. Torque wrenches used to check the tightening of car tires are set to the specified torque, and when the torque reaches that value, the wrench makes a sound to confirm that it has been tightened. Since the original torque has been confirmed by calibration equipment, the desired tightening can be achieved simply by setting the torque to the specified value.

Rotary Type
The rotary type is mainly used for torque measurement of motors, and torque meters are installed on the core of the motor via a coupling. In addition to the torque meters, peripheral devices such as a device to receive signals from the equipment and a PC for online confirmation are also required.

The torque meters measure the torsion or distortion of that shaft caused by the torque applied to the shaft, so the motor is rotated and the signal corresponding to the load is converted into a value called torque, which is then measured.

What Is an Axial Flow Fan?

An axial flow fan is an AC-powered fan used to cool equipment.

It is used to exhaust heat generated inside the equipment to the outside and, conversely, to supply air to the inside from ambient heat outside the equipment. Its main role is to control the temperature inside the equipment.

If the heat treatment of electronic components that generate heat by operating or driving equipment is left unchecked, the electronic components inside the equipment may fail or be damaged in the worst case scenario. Axial flow fans are used to supply and exhaust air from the heat generated in the equipment.

Uses of Axial Flow Fans

The main applications for axial flow fans include control panels, measuring equipment, office automation equipment, communications equipment, power supply equipment, medical and scientific equipment, amusement equipment, and industrial equipment. They are also used for ventilation and cooling of capacitors and IC electronic components in equipment such as vending machines and refrigerated showcases. The purpose of all of these applications is to ensure the long-term use of equipment.

Principle of Axial Flow Fans

A typical axial flow fan consists of a bladed plastic or metal cooling fan attached to a motor driven by an AC power source. Air is drawn in from the front of the fan and exhausted out the back to cool the inside of the equipment. Conversely, some fans intake air from the rear of the fan and exhaust air from the front.

Axial fans are fans in which the direction of airflow with the fan is in the axial direction. They are the most efficient of all turbofans and are widely used for cooling applications of heating elements. Relatively little increase or decrease in airflow due to resistive objects is a characteristic of axial fans. When axial fans are installed in equipment, the noise and power consumption of the equipment can be reduced by setting the operating point of the fan to the maximum airflow side.

The most important factor in fan performance is the required airflow relative to the amount of heat generated by the cooling target. To accommodate cooling by fans in various environments, parallel or series operation of fans, large types, or double-reversing fans may be used to obtain the required air volume.

How to Select an Axial Flow Fan

When selecting an axial flow fan, first estimate the amount of heat generated in the equipment, W. The heating value can be calculated by converting the power consumption of the equipment into heat value. Then, the allowable temperature rise value ΔT in the equipment is determined as the difference between the allowable temperature of the equipment and the maximum suction temperature of the fan. Next, the required air volume Q to satisfy the allowable temperature rise value ΔT is calculated.

The system resistance is also estimated based on the ventilation resistance in the equipment or historical data. Finally, the pressure P-airflow Q characteristic of the axial fan is used to select a fan. If it is difficult to estimate the ventilation resistance, the fan is selected so that the maximum airflow is 1.3 to 2 times the required airflow.

On the other hand, the use of a fan may cause dust and other particles to flow into the equipment to be cooled for a long period of time, which may lead to failure or damage of electronic components. In this case, a filter on the intake side in front of the fan can prevent dust and foreign matter from flowing into the equipment. This ventilation resistance must be added.

Other Information on Axial Flow Fans

1. AC Fan Motor

AC fan motors are motors driven by AC voltage. AC fan motors are composed of a stator and a rotor, and the change in the magnetic field generated when current is applied to the stator generates eddy currents in the rotor to generate power.

AC fan motors come in two types of AC power sources: single-phase and three-phase. AC motors do not normally run on single-phase alone. Therefore, single-phase AC fan motors use a built-in capacitor to advance the phase or a structure called shading. Also, motors with three-phase power supply have three different phases, so they can move if the power supply is applied as it is, and are also called induction motors.

Unlike DC fan motors, which have rotational speed control, the rotational speed of the blades is generally fixed according to the frequency of the AC power supply. There are also special ACDC fan motors that have the ability to convert AC to DC.

2. Difference Between Axial Flow Fan and DC Axial Flow Fan

The difference between an axial flow fan and a DC axial flow fan is the power source that drives the fan motor; a DC axial flow fan is a DC-powered fan. On the other hand, an axial flow fan is a fan that is driven by an AC power source.

The frequency of the AC power supply causes the fan to rotate at a constant speed, whereas the DC axial fan can change its rotation speed depending on the motor circuitry.

What Is a Crystal Oscillator?

A crystal oscillator is a device that generates a specific frequency by incorporating an oscillation circuit into the mechanical resonance of a quartz crystal unit, utilizing the piezoelectric phenomenon of quartz. These devices are known for their high precision, often on the order of ppm (parts per million).

Other types of oscillation circuits, such as LC, CR, and those using ceramic elements, are limited to percentage precision, whereas crystal oscillation can achieve greater accuracy.

Quartz’s suitability for electronic circuits is due to its piezoelectric effect, making it a vital component in technology predating transistors and integrated circuits (ICs).

Uses of Crystal Oscillators

Crystal oscillators are used in various applications, including as frequency signal sources in telecommunications equipment, timing sources in quartz clocks, and color burst signal sources in televisions. In recent times, they have become essential in providing fixed-frequency clock sources for digital circuits.

These oscillators are critical in delivering high-frequency stability and non-adjustability for ICs and LSIs (integrated circuits with higher complexity). As a result, they are utilized not only in traditional devices like telecommunications equipment, TVs, and clocks but also in satellite communications, automobiles, personal computers, DVD equipment, and other information appliances.

Principle of Crystal Oscillators

Crystal oscillators function by using a quartz crystal unit to generate a reference resonance frequency through an oscillation circuit. The piezoelectric phenomenon of quartz is key in this process. However, a quartz crystal unit alone cannot maintain the necessary amplitude of the resonance frequency.

In crystal oscillators, an internal oscillation circuit regulates the strength and frequency of the reference frequency signal. While quartz crystals in nature are composed of silicon dioxide, the quartz used in crystal oscillators is synthetic, derived from natural crystal lasca. This synthetic quartz is created under controlled conditions in an autoclave, resulting in large, pure, recrystallized artificial crystals.

Other Information on Crystal Oscillators

1. Vibration Modes of Quartz Crystal Oscillators

The temperature characteristics of frequency and vibration mode vary depending on the crystal’s cut angle relative to the crystal axis. For example, quartz crystals in wristwatches are cut to have a zero temperature coefficient at a body or room temperature.

The oscillation mode, likened to the vibration of tofu on a cutting board, is determined by the thickness of the crystal slice.

2. Accuracy of Crystal Oscillators

Normal crystal oscillators have an accuracy of about 1/10,000 to 1/100,000, significantly higher than silicon or ceramic oscillators but not as precise as cesium oscillators in atomic clocks. Temperature-compensated crystal oscillators (TCXO) offer even higher precision by incorporating a circuit that offsets the crystal unit’s temperature characteristics.

3. Crystal Oscillators Type Clock Mechanism

A quartz oscillator clock, or quartz watch, functions as a clock by converting the high-precision oscillation of a quartz oscillator into a frequency at one-second intervals by dividing the frequency by an IC. Analog clocks use this frequency to drive a step motor that moves the hands, while digital clocks use it to drive a display. Quartz watches have the advantage of long-term operation with minimal maintenance, especially models powered by solar energy or equipped with generators.

4. Comparison With MEMS Oscillators

MEMS oscillators, emerging as an alternative to quartz oscillators, are produced using semiconductor manufacturing processes, allowing for integration into electronic circuits and miniaturization. They offer advantages in frequency adjustment and power consumption, potentially surpassing crystal oscillators in market share.

5. Efforts to Increase High Frequencies

As the demand for higher communication frequencies grows, there is a push for crystal oscillators to support higher frequencies. Advances in analog circuit technology like PLL enable frequency increases, but there are challenges such as phase noise and temperature characteristics. Current developments focus on improving both the crystal unit and the oscillation circuit to support frequencies up to 100 MHz.