How to link RN400 to RS-485

Thank you for purchasing the DEKIST RN400 product.

The RS-400 output terminal of the RN485 transmitter is connected to the corresponding communication line by wire, and the measured data can be sent to equipment such as PC, PLC, and recorder.

✓ The sub-model supports serial communication using the RS485 output terminal.
RN400-T2TS (4-channel temperature transmitter)
RN400-T2 CS (4-channel 4-20mA transmitter)
RN400-T2GS (2-channel multi-gas transmitter)
RN400-T2 PM (Differential Mode, Cumulative Mode)

The above RN400 submodel only supports MODBUS RTU protocol, all data Float 32 Bit Formatis composed of.

Powered by DC 12Vonly if movementand in the case of battery operation RS-485 function이 Disabled It's possible.

1. Setting up RS485

1. Entering USB CALIBRATION – Press the W button to activate the RN400, then press the S button to enter the setup menu. When [3.USB CALIBRATION] is displayed by pressing the S button 3 times, press the W button to select the corresponding menu.
2. Connecting the device to the computer – Connect the RN400 to the PC with a Micro USB cable as shown below.

3. If you run the UA-Calibrator program on your PC, the following information and setting window appear at the top of the setting screen.

• UA-Calibrator software is provided on our website.
  – Program download path: UA-Calibrator Program Download

4. Select the operation mode (Master / Slave). When the master device reads the sensor value by requesting data from RN400, it selects Slave. In most cases, you can select Slave.

5. The communication speed (Baud Rate) is the RS-485 communication speed and is set to the same value as the device receiving data. Options include 9600 bps, 57600 bps, and 115200 bps.

6. Slave ID is an identifier to distinguish a sensor when several sensors are connected at the same time. The RN400 contains a value in the holding register. The holding register is Function Code 03.

# Timeout and ByteSwap parameters are used where a more detailed communication environment is required.

2. PC linkage demo

The explanation below is how to set RS-400 MODBUS so that the sensor value of sub model RN2-T485GS can be read from PC.

Preparations for the Demo

1.UA-Calibrator program: Downloadable
2.RS-485 Test Program: Downloadable 
3.laptop 
4.Micro USB cable
5.RN400 T2GS + Gas Sensor 
6.DC 12V power adapter
7.RS-485 Converter (Model: Sena LTC100) 

1. MODBUS RTU setting – Set RN400 as UA-Calibrator, run UA-Calibrator on the connected computer, and use the following values ​​for MODBUS RTU setting.

Baud Rate: 9600bps
Slave ID: 54

It is a value to set the baud rate and ID.

2. Connect PC to RS-485 converter and make PC ready to receive RS-485 signal.

3. Next, in the terminal block inside the RN400, connect the converter + to the RS-485 output terminal A on the left side of the power supply and the converter – cable to the terminal B. Please refer to the photo below.

The cables (+) and ( – ) wires connected to the RS-485 output terminal are twisted to prevent noise.
12V power must also be supplied for RS-485 to operate. If there is no power supply, RS-485 does not work.

4. Run the RMMS program for RS 485 test installed on the PC, select the Connection > Setting tab in the menu, select MODBUS RTU, the comfort connected to the PC, and set it to 9600 bps to synchronize it with the RN400.

5. When the following window pops up by selecting File> new tab, set to read 54 bytes from ID 0, Holding Register setting, data address 8. Select 32 bit float and press the connection icon button on the menu so that the PC can continuously read the RN400 sensor value.

6. If PC and RN400 are connected, RX/TX LED of converter will blink repeatedly.
The figure below is an example of the result of reading the value of channel 1 with RS-485 and displaying it on the PC screen.

3. RN400's data memory map

Data is expressed by the start address and the number of data.
The data unit is 16 bit word.

• RN400-T2GS

• RN400-T2CS / TS
  

• RN400-T2PM

6 channels, data address: 0x0000, data length: 12

Glossary of terms

• PLC: Programmable Logic Controller
• RS485 communication interface uses half-duplex serial message communication method using Mult-drop bus, and communication distance is relatively long.