1. Introduction
The eletechsup NT48A08 is an 8-channel RS485 NTC temperature acquisition module designed for industrial and scientific applications. This module can simultaneously measure the temperature from up to 8 NTC thermistors or the resistance value of conventional resistors, communicating via the standard MODBUS RTU protocol.
2. Features
- Standard MODBUS RTU protocol support.
- Wide operating voltage range: DC 7-25V.
- Configurable baud rates and parity bits.
- Temperature measurement range: -20 °C to +125 °C.
- Simultaneous measurement of temperature and resistance.
3. Specifications
| Parameter | Value |
|---|---|
| Operating Voltage | DC 7-25V (e.g., 9V, 12V, 15V, 24V) |
| Operating Current | 10-30mA (varies with external NTCs) |
| MODBUS RTU Command Support | 03, 04, 06, 16 function codes |
| Default Baud Rate | 9600BPS (Configurable: 2400, 4800, 19200, 38400, 57600, 115200BPS) |
| Parity Modes | No parity, Even parity, Odd parity |
| Adapted Sensor | 10K B3950 1% NTC thermistor (up to 8 channels) |
| Temperature Measurement Range | -20 °C to +125 °C (with eletechsup NTC sensor) |
| Temperature Measurement Accuracy | 1% (with eletechsup NTC sensor) |
| Resistance Measurement Range | 1K-100KΩ |
| Board Dimensions (L*W*H) | 72mm * 55mm * 15mm |
| Board Weight | 23g |
NTC Sensor Specifications (Purchased Separately)
- Product Name: 5*25mm NTC Waterproof Probe
- Total Length: 50CM
- Resistance Value: 10K
- Resistance Accuracy: ±1%
- Resistance B Value: 3950 ± 1%
- Temperature Range: -20 °C to 125 °C
- Wire Type: 2651 26# parallel line, rated for 105 °C
- Plug Model: XH2.54-2P
4. Setup
Figure 1: eletechsup NT48A08 8-Channel RS485 Temperature Acquisition Module Board.
4.1 Power Supply Connection
Connect a DC power source within the 7-25V range to the VIN and GND terminals on the module. Ensure correct polarity to prevent damage.
4.2 NTC Sensor Connection
Connect up to 8 NTC thermistors (10K B3950 1% recommended) to the designated NTC1 through NTC8 terminals. The module does not include NTC sensors; they must be purchased separately.
Figure 2: Top-down view of the NT48A08 module, highlighting connection points for NTC sensors and power input.
4.3 RS485 Communication Connection
Connect the module's RS485 interface to your Modbus master device. Ensure the A and B lines are correctly connected to their respective terminals on both devices.
4.4 DIP Switch Configuration
The module features a DIP switch for certain configurations. Refer to the dedicated MODBUS RTU Command document for specific instructions on setting the module address, baud rate, and parity using the DIP switches or software commands.
5. Operating Instructions
5.1 MODBUS RTU Protocol
The NT48A08 module operates as a Modbus RTU slave device. A Modbus master device (e.g., PLC, HMI, computer with RS485 adapter) is required to communicate with the module.
5.2 Reading Temperature and Resistance
Use standard MODBUS RTU function codes (e.g., 03 for Read Holding Registers, 04 for Read Input Registers) to query the module for temperature and resistance values from the connected NTC sensors. The specific register addresses for each channel's data are detailed in the MODBUS RTU Command document.
5.3 Configuring Baud Rate and Parity
The module's baud rate and parity settings can be configured via MODBUS RTU commands (e.g., function code 06 for Write Single Register, 16 for Write Multiple Registers) or potentially via the onboard DIP switches. It is crucial that the master device's communication settings match those of the module.
5.4 Reference Document
For a comprehensive list of MODBUS RTU commands, register addresses, and detailed configuration instructions, please refer to the official document: "NT48A08 NT48B20 NT48C32 MODBUS RTU Command".
6. Maintenance
- Keep the module clean and dry. Avoid exposure to dust, moisture, and corrosive substances.
- Operate the module within its specified temperature and humidity ranges.
- If the module is enclosed, ensure adequate ventilation to prevent overheating.
- Regularly inspect connections for secure fit and absence of damage.
7. Troubleshooting
7.1 No Power Indication
- Verify the DC power supply voltage is within 7-25V.
- Check power cable connections for proper polarity and secure contact.
7.2 Incorrect Temperature/Resistance Readings
- Ensure NTC sensors are correctly connected to their respective terminals.
- Confirm that the NTC sensors used are 10K B3950 1% thermistors.
- Review the MODBUS RTU Command document for correct register addresses and data interpretation.
7.3 Communication Failure
- Check RS485 wiring, ensuring the A and B lines are not reversed.
- Verify that the baud rate and parity settings on the module and the Modbus master device match.
- Confirm the module's Modbus address is correctly set and unique on the bus.
- Ensure termination resistors are correctly applied if necessary for the RS485 bus.
7.4 NTC Sensor Not Included
Please note that this module does not come with NTC sensors. They must be purchased separately (10K B3950 1% NTC thermistors are recommended).
