4-20 mA Sensor Board by Libelium 感測器傳訊板 適用於Arduino、Raspberry Pi 和 Intel Galileo

4-20 mA Sensor Board by Libelium 感測器傳訊板 適用於Arduino、Raspberry Pi 和 Intel Galileo

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4-20 mA電流迴板 是最強大的感測器信號標準之一。電流迴路是數據傳輸的理想選擇之一,因為它們對電噪聲不敏感。

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4-20 mA Sensor Board by Libelium  感測器傳訊板,適用於Arduino、Raspberry Pi 和 Intel Galileo

是最強大的感測器信號標準之一。電流迴路是數據傳輸的理想選擇之一,因為它們對電噪聲不敏感。

在 4-20 mA 電流迴路中,所有信號電流都流過所有組件;即使導線端接不完美,相同的電流也會流動。

由於信號電流流過它們,迴路中的所有元件都會降低電壓。只要電源電壓大於最大信號電流20 mA時,迴路周圍的電壓降低,信號電流就不會受這些影響。

當信息必須長距離(500米或更長)發送到遠程位置時,通過電流迴路傳輸感測器信息特別有用。

迴路操作很簡單:感測器輸出電壓首先轉換為比例電流,4 mA通常表示感測器0電平輸出,20 mA表示感測器滿載輸出。

遠端的接收器將4-20mA電流轉換回電壓,電壓又可以由計算機或顯示模組進一步處理。

4-20 mA電流環
類型 類似物
媒體 雙絞線
渠道數量 4
距離 900米
供應 5-24V

4-20 mA 電流迴路板 感測器傳訊板

4-20 mA 感測器傳訊板

The 4-20 mA Current Loop Board is one of the most robust sensor signaling standard. Current loops are ideal for data transmission because of their inherent insensitivity to electrical noise. In a 4-20 mA current loop, all the signaling current flows through all components; the same current flows even if the wire terminations are less than perfect.

All the components in the loop drop voltage due to the signaling current flowing through them. The signaling current is not affected by these voltage drops as long as the power supply voltage is greater than the sum of the voltage drops around the loop at the maximum signaling current of 20 mA.

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Article Index

Features Go to index

The 4-20 mA Board has 4 input channels which allow converting signals that come with this industrial standard. This shield works with type 2, 3 and 4 current transmitters. Each channel can be configured for working with these types of connections. If the jumper is retired, the receptor will be configured as float (type 4 connection).

Electrical Features

The 4-20 mA Board includes a 24 V output that can be used to supply sensors. The majority of 4-20 mA sensors work in the 9-24 V range. Before connecting a sensor to the 4-20 mA Board, you must be sure that the sensor is in this range of power supply. If you are going to use all channels, the consumption of the board will increase. Is important to know, that 4-20 mA Board is not designed to supply industrial devices such as PLC’s and thermostats.

Board

Get Arduino

Get the 4-20 mA Sensor Board

Get Raspberry Pi

Get the Raspberry Pi to Arduino shields connection bridge

Get the 4-20 mA Board

3. The Library Go to index

The 4-20 mA Board counts with a C++ library that lets you manage it in a simple way. This library offers an simple-to-use open source system.

In order to ensure the same code is compatible in all the platforms (Arduino, Raspberry Pi and Intel Galileo) we use the ArduPi libraries which allows developers to use the same code. Detailed info can be found here:

Using the library with Arduino

The 4-20 mA Board includes a high level library functions for an easy manage. Before start using this functions you should download the library. This zip includes all the files needed in several folders.

Download the 4-20 mA library for Arduino

Libraries are often distributed as a ZIP file or folder. The name of the folder is the name of the library. Inside the folder will be the .cpp files, .h files and often a keywords.txt file, examples folder, and other files required by the library.

To install the library, first quit the Arduino application. Then uncompress the ZIP file containing the library. For installing libraries , uncompress zip file. It should contain three folder called _4_20mA. Drag these folders into this folder (your libraries folder). Under Windows, it will likely be called “My Documents\Arduino\libraries”. For Mac users, it will likely be called “Documents/Arduino/libraries”. On Linux, it will be the “libraries” folder in your sketchbook.

The library won’t work if you put the .cpp and .h files directly into the libraries folder or if they’re nested in an extra folder. Restart the Arduino application. Make sure the new library appears in the Sketch->Import Library menu item of the software.

Using the library with Raspberry Pi

The 4-20 mA library for Raspberry Pi requires the ArduPi library and both libraries should be in the same path.

Download the 4-20 mA library for Raspberry Pi

Creating a program that uses the library is as simple as putting your code in this template where it says “your Arduino code here”

Code:

Compilation of the program can be done in two ways:

  • Compiling separately the 4-20 mA and the arduPi libraries, and using them for compiling the program in a second step:

  • Compiling everything in one step:

Executing your program is as simple as doing:

Using the library with Intel Galileo

The 4-20 mA Board includes a high level library functions for an easy manage. Before start using this functions you should download the library. This zip includes all the files needed in several folders.

Download the 4-20 mA library for Intel Galileo

Libraries are often distributed as a ZIP file or folder. The name of the folder is the name of the library. Inside the folder will be the .cpp files, .h files and often a keywords.txt file, examples folder, and other files required by the library.

To install the library, first quit the Arduino application. Then uncompress the ZIP file containing the library. For installing libraries , uncompress zip file. It should contain three folder called _4_20mA. Drag these folders into this folder (your libraries folder). Under Windows, it will likely be called “My Documents\Arduino\libraries”. For Mac users, it will likely be called “Documents/Arduino/libraries”. On Linux, it will be the “libraries” folder in your sketchbook.

The library won’t work if you put the .cpp and .h files directly into the libraries folder or if they’re nested in an extra folder. Restart the Arduino application. Make sure the new library appears in the Sketch->Import Library menu item of the software.

General 4-20 mA functions

General functions

4. Connecting Sensors Go to index

The majority of 4-20 mA sensors work in the 9-24 V range. Before connecting a sensor to the 4-20 mA Board, you must be sure that the sensor is in this range of power supply. If you are going to use all channels, the consumption of the board will increase. Arduino board can be supplied with an external power supply. The recommended input voltage is 7-12 V. If you need more voltage, you can use the DC-DC converter integrated in the 4-20 mA Board. This converter provides a 24 V out, and can be used to supply 4-20 mA sensors. Is important to know, that the 4-20 mA board is not designed to supply industrial devices such as PLC’s and thermostats.

To get this 24 V, is necessary to supply the Arduino board with a minimum voltage of 9 volts.

You can use the functions ON()/OFF() to enable/disable the 24 V output.

It is advisable to check that the DC-DC converter is working properly. You can measure the output voltage using a multimeter.

NOTE: This feature is not available in Raspberry Pi. The 4-20 mA sensors must be supplied externally.

Connecting sensors

In this part of the tutorial we are going to connect a 4-20 mA sensor and supply it with 24 V output. This sensor is type 2 transmitter. Type 2 transmitters are energized by the current loop, where the supply voltage is included in the receptor. The transmitter is floating and the ground is in the receptor, so is necessary to put the connect the corresponding jumper.

Upload the example code included with the library

Arduino / Intel Galileo

Code:

Raspberry Pi

Code:

In the serial monitor you should be that the sensor is transmitting 4mA. The 4mA “bottom of span” signal allows the receiver to detect a broken wire or failed instrument. The constant-current feature of a current loop cancels out voltage drop errors due to long wiring runs (of course this would also be true if you selected different current values for zero and span).

Device Compatibility Go to index

This shield is tested and fully compatible with the following boards:

Arduino Boards

  • Arduino Uno

Raspberry Pi Boards

  • Raspberry Pi
  • Raspberry Pi (Model B+)
  • Raspberry Pi 2、3

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