Introduction

Need to monitor two temperature points and transmit the readings to a PLC, HMI, industrial computer, or embedded controller?

The Eletechsup N4DSB03 is a compact, low-power temperature acquisition module designed for two DS18B20 digital temperature sensors. It converts sensor readings into Modbus RTU data and transmits them over an RS485 communication network.

With a wide supply voltage range, configurable serial communication, and a PCB footprint of only 32.6 × 25.8 mm, the N4DSB03 is a practical option for distributed temperature monitoring, embedded control systems, smart home projects, and industrial equipment.

Product page: https://eletechsup.com/products/n4dsb03-1-2ch-rs485-digital-temperature-collector-module-55-to-125c-ds18b20-sensor-dc-5v-12v-24v-for-thermostat-smart-home-r46ca01

1. Key Technical Specifications

Parameter	Specification
Model	N4DSB03
Temperature sensors	DS18B20
Acquisition channels	2
Temperature measurement range	-55°C to +125°C
Communication interface	RS485
Communication protocol	Modbus RTU
Supported function codes	03, 04, 06, 16
Supply voltage	DC 6–25V
Working current	Approximately 7–8mA
Default baud rate	9600 bps
Configurable baud rate	1200–115200 bps
Serial format	8 data bits, no parity, 1 stop bit
PCB dimensions without terminals	32.6 × 25.8 × 3.5 mm
Dimensions with terminals	32.6 × 25.8 × 12 mm
Weight without terminals	Approximately 3.6g
Weight with terminals	Approximately 7.6g

The N4DSB03 supports up to two DS18B20 sensors per module. Its compact design makes it suitable for installations where space and power consumption are important considerations.

2. Two Temperature Inputs, One RS485 Connection

The N4DSB03 allows two temperature points to be monitored through a single RS485-connected acquisition module.

For example, a controller can monitor the inlet and outlet temperatures of a cooling system, or compare the temperature inside an electrical cabinet with the surrounding environment.

Potential applications include:

• Industrial equipment temperature monitoring

• HVAC and ventilation systems

• Refrigeration and cooling equipment

• Electrical cabinets and server rooms

• Greenhouses and agricultural monitoring

• Warehouses and storage facilities

• Smart home and building automation

• Laboratory instruments and test equipment

The DS18B20 sensor provides a nominal measurement range of -55°C to +125°C. Actual measurement performance depends on the sensor, installation conditions, wiring, and system design.

3. Modbus RTU for PLC, HMI and Embedded Systems

One of the main advantages of the N4DSB03 is its RS485 Modbus RTU interface.

Modbus RTU is widely used in industrial automation because it enables a master device to communicate with multiple addressed devices over a serial network.

The N4DSB03 can be integrated into systems using compatible:

• PLCs and HMIs

• Industrial computers

• Microcontrollers and embedded controllers

• USB-to-RS485 adapters

• Python-based monitoring applications

• Custom SCADA and data acquisition software

The default serial configuration is 9600 bps, 8-N-1, with baud rates configurable from 1200 to 115200 bps.

The module supports function codes 03 and 04 for reading, and 06 and 16 for writing. Consult the official protocol documentation for the applicable register addresses, data format, scaling, and configuration commands.

4. Expandable Multi-Point Temperature Monitoring

For applications requiring more than two temperature measurement points, multiple N4DSB03 modules can be assigned different RS485 addresses and connected to a shared bus.

Each module provides two temperature channels. Therefore, a system using multiple modules can distribute temperature acquisition across different machines, cabinets, rooms, or equipment zones.

The product documentation specifies up to 247 configurable module addresses. For larger installations, Eletechsup recommends an RS485 repeater when using more than 16 modules.

The actual network capacity depends on the RS485 transceivers, bus topology, cable characteristics, master device, and repeater arrangement.

For reliable communication, use proper RS485 wiring practices and ensure each module has a unique address.

5. Example Application: Cooling System Temperature Monitoring

Consider an industrial cooling system with two temperature measurement points:

• Channel 1: Cooling water inlet temperature

• Channel 2: Cooling water outlet temperature

Both DS18B20 sensors connect to the N4DSB03. A PLC or industrial computer reads the temperature registers through RS485 Modbus RTU.

The host controller can then:

1. Display both temperatures on an HMI.

2. Calculate the temperature difference across the cooling system.

3. Record temperature trends for maintenance.

4. Generate alarms when configured temperature limits are exceeded.

5. Send measurements to a central monitoring system.

The same architecture can be adapted for refrigeration systems, heating equipment, server cabinets, environmental monitoring, and other applications requiring two-point temperature measurement.

The N4DSB03 handles temperature acquisition and communication, while the host controller implements the application-specific logic.

6. Compact PCB for OEM and Embedded Applications

With a PCB footprint of just 32.6 × 25.8 mm without terminals, the N4DSB03 can be considered for embedded equipment and custom control boards where installation space is limited.

Possible uses include:

• Temperature monitoring inside electronic equipment

• Custom thermostatic controllers

• Remote temperature acquisition nodes

• OEM automation products

• Small industrial monitoring systems

• Embedded RS485 sensor interfaces

The module supports a DC 6–25V supply, helping simplify power integration in many low-voltage control systems.

For OEM projects, engineers should check the available terminal version, mounting arrangement, wiring requirements, and enclosure design before integrating the module into a finished product.

7. Wiring and Installation Recommendations

DS18B20 sensor wiring: Connect the sensors to the appropriate channel terminals, following the official wiring diagram. Check the power, ground, and data connections carefully.

RS485 wiring: Connect A+ and B− to the corresponding RS485 interface on the master device. If communication fails, verify polarity and the terminal labels used by both devices.

Serial configuration: Start with the default settings of 9600 bps, no parity, 8 data bits, and 1 stop bit.

Sensor cable length: Eletechsup recommends keeping DS18B20 sensor leads within 15 metres.

RS485 bus length: The recommended bus length is within 100 metres. Longer runs may require additional attention to cable selection, termination, topology, and electrical noise.

Troubleshooting: Check the supply voltage, sensor wiring, Modbus address, and serial settings. The product documentation describes shorting the RES jumper for five seconds to restore factory settings if communication fails.

Conclusion

The Eletechsup N4DSB03 combines two DS18B20 temperature inputs, low power consumption, and RS485 Modbus RTU communication in an exceptionally compact acquisition module.

It is a useful option for engineers and system integrators developing PLC temperature monitoring, HMI systems, embedded controllers, smart home equipment, and distributed industrial temperature acquisition networks.

Whether you need to monitor two temperature points locally or distribute multiple acquisition modules across an RS485 network, the N4DSB03 provides a compact hardware interface for bringing DS18B20 temperature data into your control system.

Explore the Eletechsup N4DSB03:
https://eletechsup.com/products/n4dsb03-1-2ch-rs485-digital-temperature-collector-module-55-to-125c-ds18b20-sensor-dc-5v-12v-24v-for-thermostat-smart-home-r46ca01

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