Scales are designed to accept weight on the platform, and accurately provide a digital representation of that weight. In the most basic format, this weight will simply be shown on the readout display of the indicator. Often, though, the weight measurement is sent to another instrument or computer system for process control and system integration.
Modbus Weighing Systems
There are a number of communication interfaces available for use with weighing instruments. Standard RS232 would be considered a legacy standard for sending serial data. Other choices include RS422, USB, Ethernet, and Wi-Fi.
Modbus is a specialized protocol that was primarily developed for communicating with Programmable Logic Controllers, also known as PLCs. These are computers that are generally used in industrial environments for controlling production lines, automated processes, and robotic systems. The PLC is often packaged for industrial use, and easy-to-use programming systems are often employed.
Many different types of sensors are available with Modbus, including temperature sensors, humidity sensors, position sensors, and pressure sensors. The PLC can use these inputs to control a range of outputs, including valves, conveyors, motor controllers, and other devices. While “ladder logic” is the underlying software, there are an array of user-friendly overlays to ease the task of programming.
Industrial weighing can be considered to be just another sensor input to the PLC. Typically, a load cell in the scale converts weight into an electronic signal. Arlyn Scale’s Ultra Precision weight sensors are useful for higher accuracy applications.
What Is The Modbus RTU?
RTU stands for Remote Terminal Unit. Modbus RTU uses a serial interface, specifically RS232 or RS485, as a physical transmission layer for the Modbus protocol. This allows for communication between all devices using this.
An alternative is Modbus TCP. It uses Ethernet connectivity instead of a serial interface. The Industrial Protocol, known as Ethernet IP, is a well-established method for communication.
Features Of Modbus Scales
The primary feature of a Modbus scale is that it can easily communicate with Modbus controllers. Additional features are dependent on which scale is being utilized for the application. Arlyn offers a wide range of bench scales, platform scales, corrosion-resistant scales, ultra-precision scales, and even intrinsically safe scales with Modbus capability.
Good solutions rely on the efficient use of resources. Perhaps the efficient use of human resources is the best reason to turn to Modbus connectivity. It allows the user to minimize the efforts required to implement effective control of industrial applications.
It is often possible to connect many standard scales to a computer system. RS232 and USB are the most common methods. Making the connection is just the first step.
What is the purpose of getting weight data into the system? If it is simply to log this data and use it for statistical purposes, then forwarding it into a spreadsheet or database will accomplish the task. Typical uses of this type of data could be to monitor the usage of materials or determine the number of batches that have been processed, or similar.
If the goal is to provide control in real-time, sending the data to a PLC using the Modbus standard would likely be useful. It is considered to be a major advantage to be able to avoid software customization to allow this.
The rate of data communication is limited by the physical transmission layer. Modbus RTU allows baud rates as high as 115k. This is suitable for many applications where high speed is not required. Generally, weight from a scale or ambient temperature from a temperature sensor will simply not change too quickly.
Faster data transfers are enabled by Modbus TCP. The speed will be dependent on the flavor of Ethernet being used, such as 10 Mb up to 100 Mb, 1 Gb, or even 100 Gb. Real-time control becomes much more feasible.
Industrial automation is all about process control. Filling cylinders of liquified gas may seem straightforward, but there are many steps along the way. After a hose is connected to the cylinder, a valve must be turned on to begin filling.
The weight of the cylinder is monitored on a cylinder scale to determine when the filling process is complete, with the value being sent by Modbus to a PLC. This PLC is also controlling the fill valve, and possibly conveyors, labelers, and other devices.
The end goal is to connect all of the pieces into a complete system to achieve the desired process. Modbus scales, PLCs, and other devices help achieve this goal.
Using Modbus for Weight Measurements
Modbus is not available on all scales. A few, including Arlyn Scales, do offer this capability. The benefits can be quite significant.
Make Arlyn’s Modbus Scales Part Of Your Process
In the industrial world, taking advantage of the available tools will provide excellent results. Arlyn Scales’ technical team is looking forward to your call to help determine which type of scale, and which type of Modbus interface will work best for you.
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