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What is Modbus?
Modbus is a data transmission protocol developed by Modicon in 1979 for industrial control applications. It uses a master-slave architecture, where one device is in charge and requests information from multiple (slave) devices. Modbus is a simple command and control protocol that has been adapted to a number of media including TCP/IP, SMS, and wireless transceivers. Modbus is widely used for low-power, industrial controls.
Modbus is an active standard and is documented by the Modbus Organization. Wikipedia also has a brief article on Modbus. You can read more about Modbus and how it’s used in Dyacon products here, or keep reading.
Dyacon Modbus Sensors
Temperature/Pressure/Humidity
The Dyacon TPH-1 sensor uses Modbus protocol to connect to computers, programmable logic controllers (PLCs), and some data loggers. The sensor measures air temperature, relative humidity, and barometric pressure.
Wind Sensor
The Dyacon WSD-1 utilizes the same Modbus protocol to transfer information about wind speed, direction, and wind gusts to computers, PLC’s, and data loggers.
Summary
Dyacon air sensors (TPH‑1) and wind sensors (WSD‑1) use Modbus RTU frame over RS‑485 at a default data rate of 19200 kbps. The data rate was selected as a balance between low power and long cable runs, allowing for runs of over 1000 ft. The data rate may be set between 1200 bps and 38400 bps. Cat‑5 cable is a low-cost solution for extending the sensor cables.
Multiple Modbus RS‑485 devices can be connected to a single data bus, which has its own unique address. The master sends a “read” request to the specific device address, and the slave device responds with the requested data. TPH‑1 and WSD‑1 sensors are Modbus slave devices and must be connected to a master. Dyacon user manuals contain the necessary information for programming the master device.
The address, data rate, and calibration settings on Dyacon Modbus sensors can be configured through Modbus commands. The best part? No additional software, websites, or computer programs are required.
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