Gauselink Digital Temperature and Humidity Sensor Module RS485 Modbus RTU User Manual

1. Introduction

The Gauselink Digital Temperature and Humidity Sensor Module is designed for precise environmental monitoring and data acquisition. Utilizing the Modbus RTU RS485 protocol, these sensors offer reliable temperature and humidity measurements for various applications. This manual provides detailed instructions for the setup, operation, and maintenance of your sensor module.

Gauselink Temperature and Humidity Sensor Modules with example data graphs — Various Gauselink sensor models and example graphs showing relative humidity and temperature data over 24 hours.

2. Specifications

2.1 Product Parameters

Parameter	Value
Rated Voltage	5 ~ 28V DC (12V recommended)
Power Consumption	Less than 0.1W
Humidity Accuracy	±3%RH (at 60%RH, 25°C)
Temperature Accuracy	±0.3°C (at 25°C)
Humidity Range	0 ~ 100%RH
Temperature Range	-40 ~ 80°C
Communication Protocol	Modbus RTU RS485
Baud Rate	4800 bits per second (default)
Default Address	01
Humidity Resolution	0.1%RH
Temperature Resolution	0.1°C
Response Time	Less than 1s
Calibration Status	Precisely Calibrated (factory)
Origin	Mainland China
High-concerned chemical	None

Table of product parameters — Detailed product parameters for Gauselink sensor modules.

2.2 Model Variants and Features

The Gauselink sensor modules are available in several variants, primarily differing in their housing material and protection level:

GL-TH01-PVC: Features a PVC shell. This model is not waterproof but offers excellent ventilation, allowing for quicker response to temperature changes due to direct sensor contact with external air.
GL-TH02-PE: Features a PE (Polyethylene) shell. This model is dustproof (IP44) but not waterproof. Its porous cap filters dust while maintaining good ventilation and reducing vapor condensation.
GL-TH03-MT: Features a Metal shell. This model is dustproof (IP44) but not waterproof. Similar to GL-TH02-PE, it uses a porous cap for dust filtration and ventilation.
GL-TH04-MT: Features a Metal shell. This model is both waterproof and dustproof, with an IP67 protection level.

All models share the same PCB design and sensor type, ensuring consistent measurement quality across the range.

Comparison of different sensor models — Visual comparison of the different Gauselink sensor models (PVC, PE, Metal Shell, IP67).

Exploded view of a sensor showing internal components — An exploded view illustrating the internal PCB, sensor, and PVC housing of a Gauselink sensor.

Diagram of embedded advanced sensor from Switzerland — Diagram highlighting the embedded advanced temperature and humidity sensor from Switzerland, ensuring precise and stable measurements.

Power consumption diagram — The sensor's PCB is energy-saving, consuming less than 0.1 Watt, and supports a wide DC 5-28V power supply.

3. Setup and Installation

3.1 Wiring Diagram

Connect the sensor according to the following wiring diagram. Ensure correct polarity and connection to the RS485 communication lines (A and B), as well as power (VCC) and ground (GND).

Wiring diagram for Gauselink RS485 sensor — Detailed wiring diagram showing connections for RS485 A (Yellow), RS485 B (Blue), GND (Black), and VCC (Brown) for 5-28V DC power.

For connecting to a PC, a USB to RS485 converter is required. The CH340 driver for the converter must be installed on your Windows PC. If you need assistance with the driver, please contact Gauselink technical support.

3.2 Installation Methods

The sensor can be installed using two primary methods:

Panel/Wall Installation: The sensor can be mounted into an opening in a panel or wall. Refer to the table below for recommended opening diameters and panel thicknesses for each model.

Table of panel opening dimensions for sensor installation — Recommended opening diameter (D) and panel thickness (T) for panel/wall installation of different sensor models.

Bracket Installation:
- For GL-TH01-PVC: A white plastic bracket is available.
- For GL-TH02 / TH03 / TH04: A metal bracket is available.

Dimensions of white plastic bracket for GL-TH01-PVC — Dimensions of the white plastic bracket specifically for GL-TH01-PVC models.

Metal bracket for GL-TH02/TH03/TH04 sensors — A metal bracket suitable for GL-TH02, GL-TH03, and GL-TH04 sensor models.

Dimensions of metal bracket for GL-TH02/TH03/TH04 sensors — Detailed dimensions of the metal bracket for GL-TH02, GL-TH03, and GL-TH04 sensor models.

4. Operation - Modbus RTU Protocol

4.1 Basic Communication Parameters

Baud Rate: 4800 bps (default)
Data bit: 8
Stop bit: 1
Parity check: None
Verification: CRC-16/ModBus
Read Code: 0x03 (0x indicates hexadecimal)
Write Code: 0x06

4.2 RS485 Modbus Protocol Format

Table of RS485 Modbus Protocol Format — Table outlining the format for Host Sends (TX) and Client Replies (RX) for both Read and Write operations in the RS485 Modbus Protocol.

4.3 RS485 Modbus Register Definition

Table of Modbus Register Definitions — Detailed table defining Modbus register addresses, PLC addresses, function codes, and explanations for humidity, temperature, calibration, client address, and baud rate.

4.4 Communication Examples

To read temperature:

Host (TX): 01 03 00 01 00 01
Client (RX): 01 03 02 XX XX

To read humidity:

Host (TX): 01 03 00 00 00 01
Client (RX): 01 03 02 XX XX

To read both humidity and temperature:

Host (TX): 01 03 00 00 00 02
Client (RX): 01 03 04 XX XX XX XX

Data Interpretation for Negative Temperatures: If the temperature value is negative, it will be expressed in Two's Complement Notation. For example, if the sensor yields hexadecimal data FF10, its binary notation 1111 1111 0001 0000 is the Two's Complement for a negative value. To convert, flip the bits and add 1, resulting in 0000 0000 1111 0000, which is 240 in decimal. The actual temperature is -240/10 = -24°C.

Screenshot of Serial Port Tester showing negative temperature data — Example screenshot from a Serial Port Tester demonstrating how negative temperature values are displayed and interpreted using Two's Complement.

To read Baud Rate:

Host (TX): 01 03 07 D1 00 01
Client (RX): 01 03 02 00 01

To read client address:

Host (TX): 01 03 07 D0 00 01
Client (RX): 01 03 02 00 01

To change client/sensor address from 01 to 02:

Host (TX): 01 06 07 D0 00 02
Client (RX): 01 06 07 D0 00 02

If the client address is forgotten, it can be checked by using the broadcast address 0xFF as a substitute, ensuring only one client is connected. For example:

Host (TX): FF 03 07 D0 00 01
Client (RX): 02 03 02 00 02 (indicating the address is 0x02)

Screenshot of Serial Port Tester showing Modbus communication — Screenshot of a Serial Port Tester window demonstrating various Modbus commands for reading temperature, humidity, baud rate, and client address, as well as changing the client address.

4.5 Multiple Sensors and Transmission Distance

The RS485 protocol allows for long-distance data transfer and multiple sensors on a single bus:

The theoretical transmission distance for RS485 can be up to 1200 meters.
Up to 254 sensors can theoretically work together on the same bus, provided each sensor is assigned a unique address.

Diagram showing RS485 transmission distance and multiple sensor connection — Diagram illustrating the RS485 transmission distance of up to 1200m and the capability to connect up to 254 sensors, each with a unique address (e.g., 0x01, 0x02).

4.6 Video Demonstration

Watch this video for a demonstration of sensor assembly, data reading, and PC communication.

Video demonstrating the assembly of the sensor, reading data using an RS485 device, communication with a PC, and measuring temperature and humidity around a warm water bottle.

5. Maintenance and Calibration

The Gauselink sensor modules are precisely calibrated before leaving the factory, so no initial calibration is typically needed before use.

5.1 Temperature and Humidity Calibration (Offset)

Registers 0x0050 (Temperature) and 0x0051 (Humidity) are available for users to apply an offset if fine-tuning of the temperature/humidity values is required. The default value for these registers is 0.

To offset the temperature by +2°C: Set the value of register 0x0050 to 0x14.
- Host (TX): 01 06 0050 0014
- Client (RX): 01 06 0050 0014
To increase the humidity by +5%: Set the value of register 0x0051 to 0x32.
- Host (TX): 01 06 0051 0032
- Client (RX): 01 06 0051 0032

Note: Negative offset values must be expressed in Two's Complement Notation. For example, -2°C would be expressed as 0xFFEC.

6. Troubleshooting

6.1 No Output or Output Error

If you experience no output or an error in the sensor's output, consider the following common issues:

Incorrect Baud Rate: Ensure that the communication device (PC, MCU, PLC) is configured to the correct baud rate. The default baud rate for the sensor is 4800 bps.
Incorrect Wiring: Verify that the Terminal A and Terminal B wires of the RS485 connection are not mixed up. Also, check VCC and GND connections.
Missing Driver: If connecting to a PC via a USB to RS485 converter, ensure that the necessary CH340 driver has been correctly installed on your Windows operating system.
Incorrect Client Address: If multiple sensors are on the bus, ensure the correct client address is being queried. If the address is unknown, use the broadcast address (0xFF) with only one sensor connected to determine its address.

7. User Tips

For optimal accuracy, avoid placing the sensor in direct sunlight or near strong heat sources.
When using multiple sensors, ensure each has a unique Modbus address to prevent communication conflicts.
Regularly check wiring connections for looseness or corrosion, especially in humid environments.
If using the GL-TH01-PVC model, ensure it is not exposed to water as it is not waterproof.
For long cable runs, consider using shielded twisted-pair cables for RS485 to minimize interference.

8. Warranty and Support

Gauselink provides one-to-one technical support for its products. If you encounter any issues or have questions regarding the installation, operation, or troubleshooting of your sensor module, please contact our sales assistant online for assistance.

Gauselink 1 to 1 Technical Support — Gauselink offers dedicated one-to-one technical support to assist users with any product-related inquiries.

Gauselink GL-TH01-PVC, GL-TH02-PE, GL-TH03-MT, GL-TH04-MT