How do bathroom scales work, mechanical and electrical scales, which is more accurate?
Bathroom scales are devices used to measure a person's weight. They come in two primary types: mechanical (analog) scales and electrical (digital) scales. Here's how each type works and a comparison of their accuracy:
First of all let’s compare how they are different in construction
Mechanical (Analog) Bathroom Scales:
Scale Parts:
Platform: The surface where you stand.
Dial or Display: The round dial or display where the weight is shown.
Spring Mechanism: The key component that measures weight. It consists of a spring or a series of springs.
Lever System: The spring is connected to a lever system that moves a needle on the dial or display.
How It Works:
When you step onto the platform, your weight is applied to the spring mechanism beneath it.
The spring compresses or deforms under the force of your weight.
This deformation causes the lever system to move, which, in turn, moves the needle on the dial.
The position of the needle on the dial corresponds to your weight.
Electrical (Digital) Bathroom Scales:
Scale Parts:
Platform: Similar to mechanical scales, it's the surface where you stand.
Display: The digital screen where your weight is shown.
Load Cells: These are sensors (usually four) placed at the corners or beneath the platform.
Microcontroller/Processor: The brain of the scale that processes data from the load cells and displays it on the screen.
How It Works:
When you step onto the platform, the load cells under your feet experience a force.
Each load cell produces an electrical signal proportional to the force it senses.
These signals are transmitted to the microcontroller or processor.
The microcontroller processes the data and calculates your weight, which is then displayed on the screen.
Accuracy Comparison: In general, digital bathroom scales are considered more accurate than mechanical ones. Digital scales can provide weight measurements with greater precision and consistency. Mechanical scales can be affected by factors like friction, calibration issues, and the quality of the springs and levers, which can lead to less precise measurements. Digital scales are less prone to mechanical wear and tear and provide readings in a clear, easy-to-read digital format. Some digital scales also come with additional features like body composition analysis (e.g., measuring body fat percentage).
However, the accuracy of any bathroom scale, whether mechanical or digital, can be influenced by various factors, including calibration, the evenness of the surface it's placed on, and how consistently you use the scale (e.g., time of day, clothing worn). For the highest accuracy, it's important to follow the manufacturer's instructions for use and calibration.
Ultimately, the choice between a mechanical and a digital bathroom scale depends on your preferences and needs. Digital scales are generally recommended for their accuracy and ease of use.
For the more technically minded this is a brief explanation of the load cell in a digital scale. A load cell is a sensor used to measure force or load applied to it. It typically consists of several key parts that work together to convert mechanical force into an electrical signal. The basic parts of a load cell include:
Load-Receiving Element: This is the part of the load cell that directly receives and bears the applied load. It deforms under the force applied to it. The load-receiving element can take various forms, such as a strain gauge, a diaphragm, or a bending beam, depending on the type of load cell.
Strain Gauge: Strain gauges are electrical resistance elements that are bonded to or embedded within the load-receiving element. They change their electrical resistance when the load-receiving element deforms. This change in resistance is proportional to the strain (deformation) of the load cell and is the basis for measuring the applied force.
Elastic Element: Many load cells have an elastic element that allows for controlled deformation when force is applied. The elastic element helps in the distribution of the load and provides a means for strain to be measured by the strain gauges.
Wiring: Load cells have electrical wires that connect the strain gauges to a bridge circuit or other electronic components that measure the change in resistance. These wires carry the electrical signals generated by the strain gauges.
Housing or Body: The load cell is enclosed within a protective housing or body, which provides physical protection and support for the internal components. The housing is designed to be durable and resistant to environmental factors.
Mounting Points: Load cells have attachment points that allow them to be securely mounted in various applications, such as beneath a scale platform or within a testing apparatus.
Electrical Connector: Load cells typically have an electrical connector that allows for easy connection to measurement and control equipment. The connector enables the transfer of electrical signals from the load cell to external devices.
Load cells come in various designs and types, including compression load cells, tension load cells, shear load cells, and more. Each type of load cell may have variations in its internal components and configurations, but the basic principles of converting mechanical force into an electrical signal through the deformation of strain gauges remain consistent across all load cell designs. The type of load cell used depends on the specific application and the type of force being measured.
The load-receiving element in a load cell typically has strain gauges bonded to or embedded within it. Strain gauges are devices that change their electrical resistance in response to mechanical strain or deformation. When a force is applied to the load-receiving element, it deforms, causing the strain gauges to change their resistance. This change in resistance is what is measured, and it is used to calculate the applied force.
The measurement is typically taken in terms of voltage rather than current. When an electrical current is passed through the strain gauges, the voltage across them changes as the resistance changes due to strain. This change in voltage is then measured, and it is proportional to the amount of force applied to the load cell. The load cells are part of a bridge circuit, such as a Wheatstone bridge, which is used to measure the voltage change accurately. To summarize, a load cell measures the change in voltage across the strain gauges on the load-receiving element, and this voltage change is used to determine the applied force or load.
