1. Introduction
This manual provides detailed instructions for the installation, operation, and maintenance of the ComWinTop CWT-TM-2PT 2-Channel PT100/PT1000 RS485 Modbus Temperature Acquisition Module. This module is designed for accurate temperature measurement using PT100 or PT1000 sensors and outputs data via RS485 using the Modbus RTU protocol.
2. Specifications
The following table outlines the key technical specifications of the CWT-TM-2PT module:
| Parameter | Description |
|---|---|
| Power Supply | DC8~30V |
| Power Consumption | 9mA@30V, 12mA@24V, 23mA@12V, 33mA@8V |
| Input Sensor Type | PT100 or PT1000 |
| Measurement Range | -180°C ~ +650°C |
| Resolution | 0.1°C |
| Accuracy | 0.25°C |
| Sensor Connection Support | Two and three wire connections |
| Detection Features | Disconnection and short circuit detection |
| Output | RS485 (Modbus RTU protocol), isolation design |
| Working Environment | -30~+55°C / 0-95%RH |
| Material | ABS |
| Mounting Type | 35mm Din-rail |
| Dimensions | 88*72*59mm |
| Model Number | CWT-TM-2PT |
| Origin | Mainland China |
3. Setup and Installation
3.1 Terminal Description
Refer to the table below for a description of each terminal on the module:
3.2 PT100/PT1000 Wiring
The module supports both two-wire and three-wire connections for PT100/PT1000 sensors. Ensure correct wiring as shown in the diagrams below:
- Three-wire connection: Connect RTD1+, RTD1-, and GND as shown for optimal accuracy.
- Two-wire connection: Connect RTD1+ and RTD1-, and short RTD1- to GND. Note that two-wire connections may have reduced accuracy due to lead resistance.
3.3 Power and RS485 Connection
- Connect the DC8~30V power supply to the +V and GND terminals.
- Connect the RS485 communication lines to the A (D+) and B (D-) terminals.
4. Operation
4.1 RS485 Communication (Modbus RTU Protocol)
The module communicates using the Modbus RTU protocol over RS485. The default communication parameters are:
- Baud Rate: 9600 bps
- Parity: None
- Data Bits: 8
- Stop Bits: 1
- Default Device Address: 1
4.2 Modbus Register Map
4.2.1 Parameter Register Map
Use function codes 03H (read) or 06H (write) to access parameter registers:
- Address 10 (hex): Communication parameters
- BIT<7:5>: Reserved
- BIT<4:3>: Parity (00=none, 01=even, 10=odd, 11=odd)
- BIT<2:0>: Baud Rate (000=9600, 001=1200, 010=2400, 011=4800, 100=9600, 101=14400, 110=19200)
- Initial Value: 00
- Address 10 (hex), Hi byte: Slave address
- Range: 1-250
- Initial Value: 01
4.2.2 Data Register Map
Use function code 03H (read) to access data registers:
- Address 40H: Channel 1 (Format: Float, Number of bytes: 4, Property: R)
- Address 42H: Channel 2 (Format: Float, Number of bytes: 4, Property: R)
- Address 20H: Channel 1 (Format: UINT, Scale: 0.1, Number of bytes: 2, Property: R)
- Address 21H: Channel 2 (Format: UINT, Scale: 0.1, Number of bytes: 2, Property: R)
4.3 Configuration Tool
A dedicated configuration tool is provided to simplify setting up the module's parameters. This tool allows for easy modification of the slave address, baud rate, parity, and other communication settings. Data can typically be written within 255 seconds after power-up.
5. Maintenance
- Cleaning: Keep the module clean and free from dust and debris. Use a soft, dry cloth for cleaning. Avoid using solvents or abrasive cleaners.
- Environmental Conditions: Ensure the module operates within the specified working environment temperature (-30~+55°C) and humidity (0-95%RH, non-condensing).
- 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. Follow the provided instructions carefully if performing an update.
6. Troubleshooting
- No Power:
- Verify the power supply voltage is within the DC8~30V range.
- Check power connections (+V and GND) for proper polarity and secure contact.
- No RS485 Communication:
- Ensure RS485 A (D+) and B (D-) lines are correctly connected to the master device.
- Verify that the baud rate, parity, data bits, and stop bits match between the module and the master device.
- Check the module's slave address and ensure it is unique on the Modbus network.
- Confirm that the RS485 bus is properly terminated if necessary.
- Incorrect Temperature Readings:
- Check if the correct sensor type (PT100 or PT1000) is selected and connected.
- Inspect PT100/PT1000 wiring for correct two-wire or three-wire configuration as per Figure 3.
- Ensure sensor leads are not damaged or experiencing excessive interference.
- Verify the measurement range is appropriate for the application.
- Module Not Responding to Configuration Tool:
- Ensure the module is powered on and connected via RS485 to the computer running the tool.
- Confirm the correct COM port is selected in the configuration tool.
- Remember that parameters can typically only be written within 255 seconds after power-up. If this window is missed, power cycle the module.
7. User Tips
- For critical applications, always use a three-wire PT100/PT1000 connection to minimize errors from lead resistance.
- When configuring the module, it's often easiest to connect it directly to a PC with the configuration tool before integrating it into a larger Modbus network.
- Keep a record of the configured slave address and communication parameters for each module in your system to avoid conflicts.
8. Warranty and Support
For warranty information, technical support, or service inquiries, please contact your vendor or the manufacturer directly. Ensure you have your product model number (CWT-TM-2PT) and purchase details available when seeking support.