Sensors are a key component of most modern-day solutions and devices, so it’s no wonder they’re among the most popular sensors in modern space. They play a variety of roles in our digital lives, from monitoring the quality of our food to helping people recover from injuries among many other uses.
Sensors come in different forms, designs, and purposes. One class of sensors that you ought to know is the weight sensors.
As the name suggests, these sensors have everything to do with the weight of an object. In this guide, we are going to break down all that you should know about weight sensors.
What is a weight sensor?
A weight sensor is a sensor that measures the weight of an object. It works by converting the weight of an object into a digital form for easy processing and analysis.
Well, that is from a general point of view. We can now define a weight sensor from a technical angle as a type of transducer. This is a device that can convert one form of energy into another. In this case, it converts the incoming mechanical force into an electrical signal.
The weight of an object can be calculated from the electrical signal it produces.
This is a simple concept, but it’s complex in practice. The weight sensor was first developed in the 1960s and has since been used for many different applications.
Usually, these sensors are found on scales that weigh objects we buy at the market. They are also found in industrial settings to help monitor heavy machinery, heavy vehicles, and other things that weigh a lot. These sensors have also been designed to measure the weight of human beings and their health conditions as well as animals like livestock and pets among others.
These sensors are not just used for industrial purposes; they are used for many other applications as well including those meant for personal use like measuring body fat percentage among others.
They’re also used in medical facilities where they measure how much force doctors use when performing operations on patients among other uses. These sensors are found everywhere, so you should be familiar with them.
How does a weight sensor work?
To understand the working principle of a weight sensor, it will be prudent to have the basic knowledge of the whole concept of the weight measurement and the strain gauge.
A typical strain gauge is a resistor that is made of a thin strip of metal whose resistance changes when it undergoes a force. The resistance of the resistor changes depending on the amount of strain it undergoes. This change in resistance can be used to measure how much object is placed on it. This resistance is transduced into electrical values that are measured for analysis.
A weight sensor, which we can also call a weight transducer comprises numerous strain gauges that are perfectly bonded. The strain gauges in a weight sensor are arranged in two layers. This makes it possible to measure the deformation of the object as well as the load on it.
The strain gauge is a resistor whose resistance changes depending on how much force is being applied to it.
In other words, the resistance of a strain gauge decreases when there’s pressure or load on it.
A typical strain gauge has a thin metal foil that is bonded to a thick plastic substrate. The metal foil has two electrodes at each end for easy connection with other electronic components. The surface of one end of the foil has been etched to increase its sensitivity and detect small changes in resistance.
The first layer of this sensor contains strain gauges that have only one electrode at each end; this makes them sensitive to compression forces only.
When one side of this layer is compressed, or when you apply some compressional force on it, the body will behave like a spring-it will undergo a temporary deformation. However, it will resume its shape almost immediately.
Other than the physical changes, there will be a change in the resistance. This will result in voltage variation at the Wheatstone bridge circuit. The voltage change will be directly proportional to the force applied.
The Wheatstone bridge circuit will amplify the change in voltage and send it to the next component.
The microcontroller will then use this data to determine the strain on the sensor.
A load cell signal conditioner circuit is used to convert the analog signal from the Wheatstone bridge circuit into a digital signal. This signal is then sent to a microcontroller for further analysis.
The microcontroller will be connected to the load cell signal conditioner circuit and will be able to measure the load applied to the sensor and calculate its force value. The output of this circuit is an analog output that can be fed either directly or through an amplifier.
This can be used for further applications like control, monitoring, detection, control, etc.
What is weight sensor accuracy
We can define the weight sensor accuracy as the slightest amount of force that when applied to the sensor can cause a linear change in the output voltage. If a force is applied to the sensor and the output voltage remains constant then we can conclude that the sensor is not affected by that force.
This means that if a force of 1N (Newton) is applied to the load cell, then it will change its output to 3V. This can be proved by connecting two identical sensor circuits in series and making one circuit act as a load cell and the other as a weight sensor. Now if we apply 1N of force on each of these two circuits then both will show similar output.
If we increase the amount of pressure being applied to both circuits, then their outputs will become more different from each other because there is a greater change in voltage caused by a greater force.
Types of weight sensors
When it comes to buying weight sensors, you need to know which is the right type for you. The different types of weight sensors in the market include the following:
Strain gauge weight sensors
Strain gauge weight sensors work by measuring the strain that occurs when force is applied to the sensor. This type of weight sensor consists of two parts. The first part consists of a diaphragm which is fixed and the second part is a beam that is connected to it by means of a spring. The diaphragm is then compressed and when this happens, the beam will move back to its original position by measuring this movement, the strain that has occurred can be calculated.
Impedance based weight sensors
The main difference between impedance-based weight sensors, like capacitive-based weight sensors, lies in how they measure strain. In capacitive-based weight sensors, the weight sensor consists of a capacitor with a spring attached to it. The capacitor is connected to a microcontroller which is then able to measure the capacitance of the capacitor. When force is applied to the sensor, due to friction or other factors, it changes the capacitance of the capacitor and hence changes its resistance. The change in resistance is then measured by the microcontroller and can be used for calculating strain.
The main advantage of using capacitive-based weight sensors over impedance-based weight sensors are their accuracy, ease of use, and low cost.
Hydraulic based sensors
Hydraulic weight sensors work on the principle of hydraulic pressure. The force exerted by the hydraulic pressure is measured by the sensor and used to calculate strain.
Hydraulic weight sensors are very accurate and hence preferred for heavy-duty applications. It is also preferred over other types of weight sensors as it does not require any calibration process.
Advantages of strain-gauge weight sensors
There is no doubt that strain-based sensors remain to be the most popular type as compared to their counterparts. They are used in both small-scale and large-scale applications.
Here are the top reasons behind the massive popularity of strain gauge sensors;
-High accuracy levels: Strain gauge weight sensors are designed to deliver the most accurate results. This is possible given that they are designed to be highly sensitive to the pressure changes on the weight sensor.
-Ease of use: Strain gauge weight sensors are relatively simple to use. They require no calibration or adjustment at all, so they can be used with relative ease regardless of the application areas. You can install and use the sensor without having to undergo some special training.
-Strong and durable: The robust construction of the strain gauge weight sensors tells a lot about their strength and durability. The body is made of steel or aluminum. This offers maximum physical and mechanical protection. If you are looking for a sensor that can be used in any kind of environment, strain gauge weight sensors are the best pick.
-Cost-effective: The cost of strain gauge weight sensors is relatively low as compared to other types. This is because they are not as complex to design and manufacture as the other types.
-Compact and portable: Strain gauge weight sensors are compact in size making them highly portable. You can use them in any application where space is not a constraint. They also require very little power input, making them ideal for use in batteries powered applications.
-Cheap in comparison with many other types: The price of strain gauge weight sensors is comparatively cheap when compared to their counterparts. This is because they require less manufacturing effort than most other types of weight sensors do.
-Easily customized: The design of strain gauge weight sensors is not as complex as that of capacitive or inductive types. This makes it easy to customize the design. Do you want a unique shape that is not even on the market? Just talk to the manufacturer and you will have a customized weight sensor.
-A broad range of calibrations: Strain gauge weight sensors come with a wide range of calibrations. It can be calibrated from 5 grams up to 100,000 pounds. This makes it easy to choose a calibration that is perfect for your application. You don’t have to worry about the accuracy of the calibration because you can just talk to the manufacturer and they will provide you with the best calibration for your application.
Types of strain gauge-based weight sensors
Even as you prepare to buy a strain gauge weight sensor, you will discover that they are not all the same. They come in different types, designs, and models.
Here are the most common types of strain gauge weight sensors that you should know.
-In-line load cell: This is usually referred to as an in-line weight transducer. It is a type of strain gauge sensor that is used to measure the weight of an object. It can be used for applications where the weight needs to be measured at a distance from the sensor. It is quite stiff and offers high accuracy levels.
-Stand-alone load cells: These are also known as direct weight sensors or in-line load cells. They can be used for applications where you want to measure the weight of an object without having it connected to any other device or system.
-Electronic load cell: Electronic load cells are another type of strain gauge sensor that you can buy. They are also known as electronic weight sensors, electronic direct weight sensors, or just plain electronic ones. They are basically wireless devices that have a digital signal processor (DSP) in them and they come with a built-in power supply and microcontroller.
-Load button: These weight sensors have raised surface (button) non which the compressive force is applied. The low-profile design of these weight sensors makes them easy to use. You won’t strain mounting an object on the weight sensor.
-Column load cell: These are also known as column sensors. They are used for measuring the weight of objects where gravity is not a problem. They do not need any power source to operate. These sensors can be used in applications where there is no power supply in the room or for areas where there is no power supply at all
-Mechanical load cells: These are also known as mechanical direct weight sensors. They have long shafts which can be used to measure the force applied to the object being weighed. This type of sensor has a mechanical sensing element that comes with a spring mechanism that forces it to compress and expand in response to applied force, thus indicating weight.
-S-beam load cell: This type of load cell is used in applications where there is a force applied at both ends of the shaft. The load cell consists of two parts, one end has a spring-loaded needle that rests against the object to be weighed, and the other end has a transducer that measures the deflection of the needle under load.
-Thru-hole load cell: This type of weight sensor has a donut-like shape. It has a smooth inner diameter that is used for measuring the compressive force of the load. A rod connected to the load is passed through this diameter.
-Pancake load cells: These also have a central threaded hole designed for measuring tension and compressional forces. The load cell is made of a metal plate on which a hole is drilled. A shaft is attached to the load and passes through the hole.
-Open piston load cells: These are similar to free pistons but they have a small piston that moves in response to the applied force and pushes against an inner ring that creates resistance to movement of the shaft as well as provides damping effects to prevent shaking or oscillations in the weight sensor.
Weight sensor technical specifications
Before you proceed to get your weight sensor, it is vital to pay attention to the following technical specs;
-Accuracy; This represents the accuracy of your weight sensor. A good quality weight sensor will have an accuracy of +/-0.5% in either direction. A lower value means a more accurate sensor
-Resolution; This is the smallest increment that can be measured by your weight sensor. If a resolution of 0.1g is required, then you will need a resolution of 0.01g. The higher the resolution, the more accurate the measurement will be
-Range; This represents how far your weight sensor can measure from its minimum to maximum range values
-Accuracy at low and high ranges; For most devices, it is important that your weight sensors have accuracy at both low and high ranges as this will allow for better readings during different stages of design like when you are designing for a specific application or when it is time for calibration purposes
-Size and shape; The size and shape of your weight sensor will determine how large or small it is. For high-end devices, it is recommended that you use a larger form factor than for low-end devices. This allows for better accuracy and performance at both ranges of your device’s performance curve.
-Working temperature; This is not an essential factor if you are looking for a low-end device. However, the working temperature of your weight sensor will affect its performance and accuracy. For this reason, it is important that you choose a weight sensor that can work in an area with a temperature range from 0°C to 60°C
-Connectivity; The connectivity of your weight sensor will determine how easy it is to connect to other devices like your Arduino or Raspberry Pi. This will also determine how easy it is to use different types of sensors on the same board.
-Cost; This factor is important when purchasing your weight sensor as the cost can be a major factor when deciding on which type of device you should purchase. The cost of high-quality units can be significantly higher than for low-end products. You should also consider the price of any additional sensors you may need to use with your device (if applicable)
What is weight sensor calibration?
Calibration is the process of measuring the weight of an object and adjusting the sensor output to compensate for any errors in measurement.
Calibration can be performed either by a technician or with an automated calibration system.
A technician will use a scale to measure the weight of the object being used for calibration and adjust the sensor output accordingly.
An automated calibration system will use a force measurement device to accurately measure the weight of an object and then adjust the sensor output to compensate for any errors in measurement.
Steps for choosing a weight sensor
Let’s look at the foolproof steps for choosing the nest weight sensor;
-Know your application: Where do you intend to use the weight sensor? What kind of objects will you be measuring on the weight sensor? This information will help you choose the right specs for your weight sensor.
-Define the mounting characteristics of the sensor; This is important to ensure that the weight sensor will fit into the desired mounting area.
-Define the weight range of your sensor; This is important to ensure that you don’t end up with a sensor that will not accurately measure certain types of objects.
-Know the performance characteristics of your choice; This will help you decide whether or not your choice is suitable for your application.
-Know the cost of each product; This can help you to decide which product is best for your budget and workload.
-Know the warranty of each product; This can help you to decide which brand is best for your budget and workload.
-Consider the weight sensor brand: Weight sensors are designed and manufactured by different companies. Some brands are better than others; Some brands have better specs than others. Take time to know the brands before you finally settle on one.
I hope you have acquired adequate information about weight sensors. Now, you should know what type of weight sensor you need to purchase and why. If you are still confused, please feel free to ask questions.
in case you want to buy weight sensors in China, let us help you. At ICRFQ, we connect buyers to reputable manufacturers and suppliers in China. We will help you source quality weight sensors and other electronic components.
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