1. Product Overview
The PTA8D08 is an 8-channel PT100 RTD RS485 Temperature Sensor Module designed for precise temperature acquisition and data collection. It utilizes the Modbus RTU protocol for communication, making it suitable for integration into various industrial and consumer systems. This module supports both 2-wire and 3-wire PT100 sensors and offers a wide temperature measurement range.
1.1 Key Features
- 8-Channel Input: Supports up to 8 PT100 RTD temperature sensors.
- Wide Voltage Range: Operates on DC 8-30V.
- Modbus RTU Protocol: Standard communication protocol for easy integration.
- Flexible Sensor Support: Compatible with 2-wire and 3-wire PT100 sensors.
- Broad Temperature Range: Available in two versions: Type A (-40℃ to +220℃) and Type B (-40℃ to +500℃).
- High Accuracy: Temperature measurement accuracy of 1%.
- Cascadable: Multiple modules can be cascaded via RS485 by modifying the address.
1.2 Package Contents
The standard package includes:
- 1 x PTA8D08 8ch PT100 RS485 Acquisition Module
Note: PT100 sensors and DIN rail boxes are sold separately and should be selected based on your specific application needs.
2. Specifications
2.1 Module Specifications
| Parameter | Value |
|---|---|
| Working Voltage | DC 8-30V |
| Working Current | 14-25mA |
| Communication Protocol | MODBUS RTU (03 read, 06/16 write commands) |
| Serial Port Baud Rate | 9600 (default), N, 8, 1 |
| Cascading Capability | Up to 247 modules (use R485 repeater for >16 modules) |
| Supported Sensors | PT100 3-wire or 2-wire sensors |
| Temperature Measurement Accuracy | 1% |
| Dimensions (L x W x H) | 136 x 92 x 32mm |
| Weight | 166g |
| Output Current | <20MA |
| Output Frequency | DC-DC |
| Output Power | 1 - 50W |
| Output Type | Multiple |
| Customization | Yes |
| Certification | None |
2.2 PT100 Sensor Specifications
| Parameter | Type A | Type B |
|---|---|---|
| Type | PT100 | PT100 |
| Probe Diameter | 6.5mm | 4mm |
| Probe Length | 30mm | 30mm |
| Probe Material | Stainless steel | Stainless steel |
| Cable Length | 0.5M | 0.5M |
| Sheath Type | PTFE sheath 3-Wire type | PTFE sheath 3-Wire type |
| Temperature Range | -200℃ to +550℃ | -50℃ to +200℃ |
| Nominal Accuracy | 0.1% | 0.3% |
2.3 DIN Rail Box Parameters
| Parameter | Value |
|---|---|
| Product Model | UM80 |
| Color | Green |
| Width | Suitable for PCB board width UM80 (80mm) |
| Insulation Grade | Flame-retardant VO grade |
| Backplane Length | Suitable for 117 mm PCB boards |
| Net Weight | 89g |
| Installation | DIN35 and C45 rail |
3. Setup and Installation
3.1 Power Supply Connection
Connect a DC 8-30V power supply to the module's power input terminals. Ensure correct polarity (DC 8-30V, GND).
3.2 PT100 Sensor Wiring
The PTA8D08 module supports both 2-wire and 3-wire PT100 sensors. Refer to the diagrams below for correct wiring.
3.2.1 3-Wire PT100 Sensor Wiring
For 3-wire PT100 sensors, connect the red wire to the P+ terminal. The other two wires of the same color (typically white) should be connected to the P- and GND terminals. The specific order of P- and GND for the two same-colored wires does not matter.
3.2.2 2-Wire PT100 Sensor Wiring
For 2-wire PT100 sensors, connect the red wire to the P+ terminal and the blue wire to both the P- and G terminals. A jumper wire can be used to connect P- and G if needed.
3.3 RS485 Bus Wiring
The PTA8D08 module communicates via RS485. Ensure proper connection of A+ and B- terminals to your RS485 master device (PC or PLC).
4. Operation
4.1 Modbus RTU Protocol
The PTA8D08 module communicates using the standard MODBUS RTU protocol. It supports function code 03 for reading data and function codes 06 or 16 for writing data.
The serial port baud rate is 9600 (default), with N, 8, 1 parity settings.
For detailed register addresses and data formats, please refer to the "PTA8D08 8CH PT100 RS485 sensor protocol" document (typically available from the manufacturer).
4.2 Reading Temperature and Resistance Values
Using the Modbus RTU protocol, you can read both the temperature and the PT100 resistance value from the module. The temperature data is typically scaled (e.g., 0.1°C per unit), and resistance values are also provided in a scaled format.
Example register usage (as seen in the video):
| Register Address | Description | Units | Remarks |
|---|---|---|---|
| 0x0000-0x0003 | CH0-CH3 Temperature value | 0.1°C | Data 255 = 25.5°C |
| 0x0020-0x0023 | CH0-CH3 PT100 resistance value | 0.1 Ω | Data 1000 = 100.0 Ω |
| 0x0040-0x0043 | CH0-CH3 Temperature correction value | 0.1°C | Input correct temperature value for correction if deviated. |
| 0x0060-0x0063 | CH0-CH3 PT100 resistance correction positive value | 0.1 Ω | If the PT100 resistance is deviated. |
| 0x00FA | Automatic upload of temperature |
4.3 Modifying RS485 Address
The RS485 address of the module can be modified to allow multiple modules to be cascaded on the same bus. Each module must have a unique address. If cascading more than 16 modules, an R485 repeater is recommended.
4.4 Modbus Communication Demonstration
The following video demonstrates how to communicate with the PTA8D08 module using Modbus Poll software, including reading and writing register values for temperature and correction.
5. Troubleshooting
- No Communication:
- Verify power supply (DC 8-30V) is correctly connected and active.
- Check RS485 A+ and B- wiring for correct polarity and secure connections.
- Ensure the serial port settings (baud rate, parity, data bits, stop bits) on your master device match the module's default (9600, N, 8, 1).
- Confirm the module's Modbus address is unique and matches the address used by the master device.
- If using multiple modules, ensure an R485 repeater is used if more than 16 modules are cascaded.
- Incorrect Temperature Readings:
- Check PT100 sensor wiring (2-wire or 3-wire) against the diagrams in Section 3.2.
- Ensure the correct PT100 sensor type (Type A or Type B) is being used for the expected temperature range.
- Verify the sensor is properly installed in the environment being measured.
- Consider applying a temperature correction value if a known offset exists (refer to Modbus register 0x0040-0x0043).
- Module Not Responding:
- Disconnect and reconnect power to reset the module.
- Check for any physical damage to the module or wiring.
- Ensure the working current (14-25MA) is within expected limits.
6. Maintenance
The PTA8D08 module is designed for reliable operation with minimal maintenance. Follow these guidelines to ensure longevity:
- Environmental Conditions: Operate the module within its specified temperature and humidity ranges. Avoid exposure to extreme temperatures, direct sunlight, moisture, or corrosive environments.
- Cleaning: If necessary, gently clean the module's exterior with a soft, dry cloth. Do not use harsh chemicals or abrasive materials.
- Connections: Periodically check all wiring connections to ensure they are secure and free from corrosion.
- Firmware Updates: Check the manufacturer's website for any available firmware updates that may improve performance or add features.
7. User Tips
- Sensor Selection: When choosing a PT100 sensor, it is recommended to select a version with a smaller range that still meets your measurement requirements for potentially better accuracy within that specific range.
- Modbus Software: For initial setup and testing, Modbus Poll or similar Modbus master software can be very helpful to verify communication and read/write registers.
- Address Management: Keep a clear record of the Modbus addresses assigned to each module in a multi-module setup to avoid conflicts.
8. Warranty and Support
For warranty information, technical support, or further inquiries regarding the PTA8D08 module, please contact the manufacturer or your authorized reseller. Ensure you have your product model number (PTA8D08) and any relevant purchase details available when seeking support.
For more information, please contact us directly.