月: 2023年9月

What Is a Bimetallic Thermostat?

A bimetallic thermostat is a temperature control device that uses a piece of metal known as a bimetallic strip, which changes its shape in response to temperature fluctuations.

Thermostats that employ contacts made of two dissimilar metals, laminated together and referred to as bimetallic strips, are generally categorized as bimetallic thermostats. This time-tested method offers exceptional weather resistance and reliability.

Uses of Bimetallic Thermostats

Bimetallic thermostats find application in a diverse range of scenarios due to their dependable performance and straightforward design. They are commonly employed in devices and systems requiring temperature regulation. Examples include temperature control in household appliances like refrigerators, air conditioners, and water heaters.

They are also used in electronic and electrical equipment to safeguard against overheating damage. When the bimetal detects a specific temperature threshold, it can interrupt the electrical circuit, providing equipment protection. Instances include computer power supplies and electric heaters.

Moreover, they can be used for triggering alarms when temperatures fall outside a designated range. They are frequently used in greenhouses and laboratories to signal temperature deviations beyond desired limits.

Owing to their reliability and ruggedness, bimetallic thermostats have widespread utility in applications related to temperature control and control circuit operations.

Principle of Bimetallic Thermostats

Bimetallic thermostats function through the utilization of a bilayer metal strip known as a bimetallic strip. Bimetals consist of two metal layers with distinct coefficients of thermal expansion. As each metal layer has a different coefficient of thermal expansion, one layer expands or contracts more than the other in response to temperature fluctuations.

This differential expansion or contraction leads to an alteration in the overall shape of the bimetal. Common metals used include chromium and manganese alloyed with iron and nickel alloys for the high-expansion coefficient side, and iron and nickel alloys with lower expansion coefficients for the low-expansion coefficient side.

Iron and nickel are chosen due to their affordability, ease of processing, and durability. Bimetallic thermostats are devices that harness the shape change of bimetals to control temperature. Typically, the bimetal is anchored at one end with a connected contact or switch located at the other end.

As temperature rises, the difference in expansion rates between the metal layers causes one layer to expand significantly, bending the entire device and actuating the contacts or switches.

How to Choose a Bimetallic Thermostat

When selecting a bimetallic thermostat, several crucial factors should be taken into account:

1. Rated Voltage

Verify the voltage rating of the bimetallic thermostat based on the specifications of the electrical equipment and circuit it will be used with. Ensure that the chosen voltage does not exceed the maximum allowed by the product; common products support voltages ranging from around 100 V AC to 250 V AC.

2. Current Rating

Consider the current rating per the electrical equipment and current requirements. It is important to avoid exceeding the rated current, which can result in issues such as contact welding. Selecting a thermostat with an appropriate current rating ensures proper operation and reliability.

These thermostats are frequently used in control circuits, with products commonly rated at 20 A or lower. Smaller units may have ratings as low as 3 A.

3. Temperature Setting Range

Determine the required temperature range for the specific application and choose suitable products accordingly. Many products only operate within certain temperature ranges. Temperature setting options encompass a wide range, spanning from a few degrees Celsius to several hundred degrees Celsius.

4. Reset Type

The reset type of the contact is also a crucial consideration. There are two types: automatic reset and manual reset. Automatic reset thermostats revert to their original state automatically when the temperature returns to the specified range.

Manual reset types require manual intervention to reset them once they have been triggered. Selection should align with the intended application.

What Is a Torque Screwdriver?

A torque screwdriver is a screwdriver designed for precise tightening to a specific torque.

It is an essential tool for tasks that demand accuracy in torque application. Torque screwdrivers can be set to specific torque values.

Correct torque application prevents damage or breakage of components. Additionally, torque screwdrivers provide consistent torque, independent of the operator’s strength, contributing to improved work quality and reliability.

Uses of Torque Screwdrivers

Torque screwdrivers have a wide range of applications, with a common use case being machine maintenance, especially in the automotive industry.

1. Automotive Industry

Torque screwdrivers are invaluable for tightening various automobile components, such as wheel nuts and suspension parts. Precise torque application ensures safety and prevents damage or loosening of parts.

2. Aerospace

In the aerospace industry, torque screwdrivers play a crucial role in maintenance and servicing. Aircraft components require precise torque control to ensure reliability. Torque screwdrivers may also be used during the production of various industrial products.

3. Electronics

In the electronics field, torque screwdrivers are commonly used for assembling motherboards in computers and mobile devices. They are also employed when tightening larger mechanical components like cylinder heads and crankcases to specific torque values.

Principle of Torque Screwdrivers

Torque screwdrivers typically employ a spring mechanism. This spring is positioned between the body of the torque screwdriver and the screwdriver head, compressing or extending when rotary force is applied.

When a certain rotational force is applied to the spring, the internal mechanism signals the user through a clicking sound and tactile feedback. This ensures that tightening is performed at the designated torque value.

Additionally, torque screwdrivers feature a torque setting mechanism, often with a torque adjustment knob or dial that can be set to the desired torque value. Some torque screwdrivers include a release mechanism that disengages and clicks out if over-torquing occurs.

Types of Torque Screwdrivers

There are various types of torque screwdrivers, each with distinct characteristics. Here are examples of different types:

1. Digital Type

Digital torque screwdrivers are equipped with a liquid crystal display and can monitor real-time torque during tightening. They allow the operator to set a target torque, providing feedback through sound or other means when the target is reached. Digital models use advanced sensors and control circuits for precise torque control.

Some digital models can also record torque data, storing torque values, operation dates, and times. This is valuable for quality control and troubleshooting.

2. Pre-set Type

Pre-set torque screwdrivers have a dial or similar mechanism for specifying torque. They do not require batteries, ensuring no risk of power depletion. Many pre-set types are non-reversible and cannot tighten further once the set torque is reached.

3. Single-Function Type

Single-function torque screwdrivers do not have adjustable settings and are calibrated using a torque screwdriver tester or similar equipment. These are used for repetitive tasks where the specified torque remains constant, providing error-proofing for operators. In many cases, torque can only be applied in one direction, typically in the clockwise tightening direction.

What Is a Tension Meter?

A tension meter is a device used to measure the stress or force resulting from the tension or stretching of an object or material.

It is commonly employed for strength testing, quality control, and research and development on metallic and synthetic materials. Tension meters can be applied to a wide range of materials and products, including metals, plastics, and textiles.

They are versatile and can be used on objects of various sizes, from small parts to large structures.

However, it is essential to observe safety precautions when using tension meters, particularly when measuring high stresses and forces. Proper safety procedures and equipment should be employed to mitigate the risk of injury.

Uses of Tension Meters

Tension meters are versatile measuring devices with applications across multiple industries and research areas. They are commonly used to measure tensile strength and stretch properties of metallic and synthetic materials, enabling the assessment of material strength and durability in quality control and product development. Tension meters are also widely employed in textile and fabric production processes.

These devices find use in material testing and component evaluation within the automotive and aerospace sectors, including testing vehicle safety belts and aircraft cables. Tension meters are also crucial for measuring tension applied to film during various processes.

In film rolling processes, maintaining correct tension is essential for consistent quality, and tension meters are used to control and ensure proper tension levels.

Principle of Tension Meters

The principles behind tension meters vary depending on their type, but they often rely on sensors called strain gauges. Strain gauges are long, thin sensors made of metal foil or semiconductor strips.

They undergo minute deformations or displacements caused by applied forces or stresses. Strain, the minute deformation or displacement resulting from stretching or compression, affects the shape of the strain gauge, causing changes in its resistance. These changes in resistance are proportional to the strain.

In tension meters, strain gauges are integrated into a bridge circuit. This circuit is initially balanced, resulting in zero output voltage. However, strain-induced changes in resistance unbalance the bridge circuit, generating an output voltage. This output voltage corresponds to the strain in the strain gauge and is then converted into stress, which is displayed and transmitted.

Types of Tension Meters

There are several types of tension meters, and the following are examples of these types:

1. Web Tension Meter

Web tension meters are employed to measure the tension of web-like materials such as fabrics and films. A sensor attached to the web expands and contracts to measure tension. They are used for various materials, including paper, plastic film, and metal foil.

Many web tension meters can monitor tension fluctuations in real-time. This enables the detection of tension anomalies as the web passes through the production line, thereby controlling product quality and production efficiency.

2. Wire Rope Tension Meters

Wire rope tension meters are used to measure the tension of wire ropes. An internal sensor is attached to the wire rope and measures tension as the rope deforms.

These meters are typically constructed from durable materials and are known for their longevity. They provide reliable measurements over extended periods and in harsh environments. They are used in various industries where wire ropes are employed, such as cranes and lifts, ensuring safe tensioning and monitoring during the lifting and movement of heavy loads.

3. Spring-Loaded Tension Meters

Spring-loaded tension meters, also known as tension gauges, do not require a power supply and are highly portable. They are commonly used for machinery and equipment maintenance.

What Is a Tact Switch?

A tact switch is an electronic component whose contacts close momentarily when a button is pressed.

It typically consists of a small, thin plastic button with soldered contacts on a PCB. Tact switches are also known as momentary contact switches.

Tact switches have a compact, slim design, making them suitable for integration into small devices. This feature helps save space in device design.

They are available at a relatively low cost, making them an economical choice for mass-produced electronics and appliances.

Uses of Tact Switches

Tact switches find applications in various fields and functions.

1. Office Automation Equipment

One common application is in office automation equipment, such as computer keyboards and mice, where they serve as buttons and operating switches. Tact switches are also used for volume control in portable electronic devices like smartphones and portable audio players.

2. Home Appliances

Tact switches are widely used in household appliances, including TV remote controls and audio equipment. They function as buttons for controlling actions like channel switching and play/stop.

3. Medical and Measuring Equipment

These switches may also find use in medical and measuring equipment for interface functions, such as operation buttons and parameter adjustments. They are employed in devices like sphygmomanometers and thermometers.

Principle of Tact Switches

Tact switches consist of several key components, including a button cap, contact points, pins, and a plastic case.

1. Button Cap

Located at the top of the tact switch, the button cap is the part that users press. It is often made of plastic and is designed for ease of operation. The button cap may also feature markings or symbols corresponding to its function or purpose.

2. Contact Points

These are the electrical circuit components that temporarily connect when the button is pressed. They are usually made of a metal spring or catalytic metal. To reduce electrical resistance, contacts are often made from materials like silver alloys or gold. Silver alloys are commonly used due to their low electrical resistance, while gold, despite being more oxidation-resistant, is pricier and used for lighter loads. These contacts are designed for durability and can withstand 100,000 to 10 million uses.

3. Pins

Tact switches have soldered pins used for mounting on circuit boards. These pins are soldered to dedicated pads on the board and carry electrical signals.

4. Plastic Case

In addition to pins, the components mentioned above are typically housed within a plastic case. This case provides mechanical protection for the components and securely attaches them to the circuit board.

Types of Tact Switches

Tact switches are broadly categorized into two types: through-hole and surface-mount.

1. Through-Hole Type

Through-hole tact switches are soldered directly into holes drilled into the circuit board, offering robust physical connections. This design ensures highly reliable operation, even in the presence of shocks and vibrations. They can handle relatively high currents and voltages, making them suitable for high-capacity electrical circuits and applications.

2. Surface-Mount Type

Surface-mount tact switches are soldered directly onto the surface of the circuit board. They enable compact designs, occupy minimal board space, and are suitable for small devices and integrated circuits. Direct contact with short traces and pads on the board ensures high signal quality, minimizing signal loss and noise effects. These switches are also conducive to efficient soldering with automatic machines, resulting in high production speeds and cost-effective mass production.

What Is a Step Attenuator?

A step attenuator is a circuit or device that can attenuate a signal by a specified amount without distorting it.

It is a device that combines several types of attenuators with different attenuation levels, and the attenuation level can be adjusted by switching a dial. It is used to protect the input stage in measuring instruments such as spectrum analyzers.

Uses of Step Attenuators

Typical applications of step attenuators include signal level adjustment and impedance matching functions.

1. Level Adjustment Attenuator

If the signal level is too high for the subsequent circuit or device when connected, the signal level is adjusted to an appropriate level before being sent to the subsequent stage.

2. Impedance Matching Attenuator

If the impedances of the sending and receiving sides are not matched when connecting an input signal to a subsequent circuit, it may result in noise generation or signal reflections, causing inconvenience to the expected operation.

The step attenuator is used to serve as an impedance-matching function to prevent such inconveniences.

Principle of Step Attenuators

A step attenuator consists of several attenuators connected in series via switches, and the attenuation can be adjusted by switching these switches. By switching the use of each attenuator, a constant attenuation step can be achieved.

For example, if seven different attenuators are used, there are 128 possible combinations of attenuator use, and the amount of attenuation is adjusted by performing signal control for seven bits.

Construction of Step Attenuators

Step attenuators have a simple structure consisting of a combination of resistors in series and parallel. The resistors are combined in T- and pi-circuits, referred to as T- and pi-circuits respectively. The voltage dividing ratio of the resistors determines the amount of attenuation.

Step attenuators also have multiple stages or subordinate connections of T- and π-shaped circuits respectively to achieve a predetermined amount of attenuation. The attenuation can be adjusted by switching the resistance value with a dial.

Additional Information on Step Attenuators

1. Example of Use in TV Receivers

If the goal is to simply attenuate the signal, this can be achieved by inserting an appropriate resistor. However, consider the case of a TV receiver used to evaluate the reception performance of TV broadcasts. To evaluate the reception quality across the 470-710 MHz frequency range used in digital terrestrial broadcasting, a step attenuator is required to attenuate the signal uniformly at all frequencies while maintaining impedance, making resistors inadequate for this purpose.

2. Example of Use as a Measuring Element

Step attenuators can also serve as measuring elements. Here is an example of how a step attenuator can be used to measure the gain of an amplifier:

A voltmeter is connected to the input of the amplifier, while another voltmeter is connected to the output side of the amplifier through the step attenuator. The step attenuator is adjusted until both voltmeter readings match the input voltage.

When the voltmeter readings at the input and output match, it indicates that the attenuation of the step attenuator is equal to the amplification of the amplifier. Consequently, the amplifier’s gain can be measured based on the step attenuator’s set value.

What Is Shrink Film?

Shrink film is a film that contracts when heat is applied, commonly used for packaging a diverse range of products due to its ability to tightly conform to their shapes.

Uses of Shrink Film

Initially used for insulating capacitors, shrink film has found widespread use in packaging, driven by the need for improved safety in food and general products. This material, typically a thermoplastic resin, is versatile, allowing multiple deformations upon heating. It boasts high gloss, transparency, water and cold resistance, and mechanical strength. These properties make it an attractive and secure packaging choice, preventing product tampering and damage.

Shrink film wraps around various products, including food bottles, toothpaste tubes, cosmetics boxes, books, DVDs, and more.

Principle of Shrink Film

Shrink film operates on a simple principle: heat application causes it to shrink and adhere to the product it encases. It comes in several types, each with specific characteristics:

1. Vinyl Chloride

Valued for its transparency, formability, and flame resistance, vinyl chloride shrinks at lower temperatures. However, its tendency for spontaneous shrinkage and lower strength are drawbacks.

2. Polypropylene

Noted for its transparency, cold resistance, and moisture resistance, polypropylene is cost-effective but has natural shrinkage and weaker strength.

3. Polyethylene

Polyethylene offers superior mechanical strength compared to polypropylene and is effective for large packaging due to its good shrinkage properties. Its disadvantages include lower transparency and slower shrinkage time.

4. Polystyrene

Polystyrene boasts excellent transparency and heat shrinkability. However, it is susceptible to impact and organic solvents, with natural shrinkage as a downside.

5. Polyolefin

Polyolefin excels with its high shrinkage rate, resistance to wrinkling and creasing, and high tear strength. It is processed at relatively low temperatures, safeguarding the wrapped product. The higher cost and difficulty in opening are its cons.

6. Polyethylene Terephthalate

Commonly known as PET, this resin features excellent transparency, mechanical strength, chemical resistance, and dimensional stability. However, it is challenging to process and open.

Features of Shrink Film

Shrink film is distinguished by its heat-induced shrinkage, conforming to the product shape, combined with excellent water and cold resistance, and mechanical strength. It’s particularly useful for packaging due to its aesthetic appeal, operational efficiency, and tamper-evident properties.

1. Design Features

With its large display area, shrink film allows for effective product promotion and multi-colored printing. It’s frequently used for packaging products like boxed tissues and instant noodles.

2. Operational Efficiency

Shrink film facilitates the bundling of products such as yogurts or beverage packs, enhancing efficiency in transportation and display.

3. Product Protection and Tamper-Resistance

Once torn, shrink film doesn’t revert to its original state, providing evidence of tampering. It’s especially useful for sealing products like jam jars, where only the lid part is wrapped, indicating if the jar has been opened.