Remote IO Module Wireless Signal Collection and Transmission

When it comes to industrial field signals, those who have been in the industrial sector for a long time are probably familiar with the terms "analog signals" and "switching signals." These two types of signals have solved most of the industrial signal transmission problems in current automation systems. Today, let's take a closer look at the characteristics of these signals and the scenarios in which they are applied.

Analog Signals

First, let’s discuss what analog signals are, starting with their basic concept. Analog signals are continuous physical quantities, typically represented as voltage or current. Most of the signals collected by sensors are analog signals, which vary continuously. For example, signals from temperature and humidity sensors or light sensors are continuous and can be categorized as analog signals.

Switching Signals

Another type of signal is switching signals. The key difference from analog signals is that switching signals are discrete, consisting of only two states: “on” and “off” (or “closed” and “open”). These signals can be further divided into two types: active (wet contact) and passive (dry contact). For example, limit switches and float switches are typically switching-type sensors. Wet contact sensors are usually polarized, while dry contact sensors do not require polarity considerations.

The International Electrotechnical Commission (IEC) has established the standardized ranges for process control system signals: current signals between 4mA and 20mA (DC), and voltage signals between 1V and 5V (DC). Sensors that conform to this standard are referred to as transmitters.

Typically, sensors output either current or voltage signals. However, these signals can be susceptible to interference during transmission, which affects long-distance transmission and processing by control devices. This is where remote IO modules come into play.

The Role of Remote IO Modules

Using remote IO modules not only reduces signal attenuation but also saves on equipment investments and cabling costs.

Sensors collect signals and convert various physical quantities (such as temperature, humidity, etc.) into a 4mA~20mA (DC) current signal. These current signals can then be directly collected by remote IO modules, which output the data in the standardized ModBus protocol. This creates a unified communication protocol for signal transmission.

In most cases, serial remote collection modules typically convert the 4mA~20mA (DC) signals to the ModBus RTU protocol, while Ethernet remote collection modules convert the signals to the ModBus TCP protocol.

Remote Industrial Control Systems

In industrial control systems, remote IO modules collect data from sensors and convert it into the ModBus protocol. This allows for long-distance transmission of data via serial or Ethernet interfaces. Ethernet devices can be directly connected to switches or routers to form a local area network (LAN), which enables data to be uploaded to the cloud for remote monitoring. This is the foundation of the Industrial Internet of Things (IIoT).

With the help of devices such as PLCs, HMIs, or industrial computers, automated control of equipment can be achieved. The integration of these systems allows for efficient data collection, processing, and control, supporting the advancement of industrial automation and IoT technologies.