AMPTI04: 4-Channel PT100 Temperature Acquisition Module with RS485 Modbus RTU

AMPTI04 is a 4-channel PT100 RTD temperature acquisition module designed for industrial temperature monitoring, remote data collection, and automation systems.

Supporting both 2-wire and 3-wire PT100 sensors, the AMPTI04 measures temperatures across a published range of -40°C to +300°C and transmits measurement data to a host controller through an RS485 interface using the Modbus RTU protocol.

The module is designed for integration with PLCs, industrial computers, HMIs, and other Modbus-compatible devices. Its four independent temperature inputs allow users to monitor multiple measurement points with a single compact device.

For developers and system integrators, the AMPTI04 offers a convenient way to add PT100 temperature measurement to an existing industrial control system without designing a dedicated RTD acquisition circuit from scratch.

2. Key Features

Four Independent PT100 Temperature Inputs

The AMPTI04 supports four PT100 temperature sensors, allowing users to collect temperature data from four separate locations.

PT100 sensors are widely used in industrial applications because of their stable, repeatable resistance-temperature characteristics. They are suitable for monitoring machinery, process equipment, heating systems, and industrial environments where reliable temperature measurement is required.

Wide Temperature Measurement Range

The AMPTI04 has a published measurement range of -40°C to +300°C.

This range makes it suitable for many general industrial monitoring tasks, including equipment temperature monitoring, process heating, HVAC systems, and thermal management applications.

The module's published measurement accuracy is 1%. For applications requiring tighter tolerances, users should confirm the exact accuracy definition, sensor contribution, and calibration requirements with the manufacturer.

Standard RS485 and Modbus RTU Communication

The module communicates through RS485 using the Modbus RTU protocol.

It supports standard Modbus read and write function codes, including 03, 04, 06, and 16, as documented in the product specifications. This enables integration with compatible PLCs, HMIs, industrial PCs, and software-based monitoring systems.

Electrical Isolation and Interference Protection

The AMPTI04 features documented 3000 VDC RS485 communication isolation protection and a communication circuit designed for improved interference immunity.

These features can help when integrating temperature acquisition into electrically noisy industrial environments. Correct grounding, wiring, shielding, and installation practices remain essential.

Flexible Power Supply

The module operates from a DC 7–25 V supply, making it compatible with commonly used 12 V and 24 V industrial power systems.

Its published operating current is approximately 14–18 mA, making it suitable for continuous temperature acquisition applications.

DIN-Rail Installation

The AMPTI04 is designed for DIN-rail installation in industrial control cabinets and electrical panels.

Its compact enclosure helps simplify installation alongside PLCs, power supplies, communication interfaces, and other automation equipment.

3. Technical Specifications

Parameter Specification
Manufacturer Eletechsup
Model AMPTI04
Function 4-channel temperature acquisition
Supported sensors PT100 RTD
Sensor wiring 2-wire or 3-wire
Measurement range -40°C to +300°C
Published measurement accuracy 1%
Communication interface RS485
Communication protocol Modbus RTU
Power supply DC 7–25 V
Operating current Approximately 14–18 mA
RS485 isolation protection 3000 VDC
Default baud rate 9600 bps
Default parity None
Default serial format 9600, N, 8, 1
Supported baud rates 1200 to 115200 bps, selectable
Installation DIN rail
Dimensions 125 × 70 × 30 mm
Weight Approximately 114 g

Specifications are based on the published Eletechsup product information. Please verify the current manual for the latest specifications and configuration details.

4. How Does the AMPTI04 Work?

The AMPTI04 reads resistance changes from connected PT100 sensors and converts the measurements into digital temperature data that can be accessed by a Modbus master.

A typical installation involves the following steps:

  1. Connect up to four compatible PT100 sensors to the corresponding input terminals.

  2. Supply the module with a suitable DC voltage within its specified operating range.

  3. Connect the RS485 A and B terminals to a compatible USB-to-RS485 adapter, PLC, or industrial controller.

  4. Configure the Modbus slave address and serial communication parameters.

  5. Use a Modbus master to read the temperature registers.

  6. Display, log, analyze, or use the temperature readings for automatic control.

For example, a PLC can read temperatures from four points on a production machine and activate cooling fans or trigger alarms when predefined temperature limits are exceeded.

5. Real-World Software Integration: A GitHub Python Example

A useful reference for developers is the public GitHub repository ctch3ng/modbus_playground.

The repository explicitly lists the Eletechsup AMPTI04 as supported hardware and includes a Python example named ampti04_4ch_pt100_read_loop.py, created to read the module's temperature registers repeatedly.

This is particularly useful for engineers who want to test the hardware through a computer before integrating it into a PLC or a larger industrial monitoring system.

Hardware Required

A basic test setup includes:

  • One Eletechsup AMPTI04 temperature acquisition module

  • Compatible PT100 temperature sensors

  • A suitable DC power supply

  • A USB-to-RS485 adapter

  • A computer running Python 3.9 or later

  • The Python MinimalModbus library

Software Workflow

The general workflow is straightforward:

  1. Connect the AMPTI04 to the computer through the USB-to-RS485 adapter.

  2. Identify the correct serial port, such as COM3 on Windows or /dev/ttyUSB0 on Linux.

  3. Install Python and the MinimalModbus library.

  4. Configure the serial port, baud rate, parity, and Modbus slave address.

  5. Read the appropriate temperature registers using the register addresses documented for the module.

  6. Repeat the read operation to monitor temperature changes over time.

The GitHub example demonstrates repeated register reading rather than a one-time measurement. This makes it a useful starting point for developing data logging, temperature dashboards, and automated monitoring applications.

GitHub source code:
https://github.com/ctch3ng/modbus_playground/blob/main/ampti04_4ch_pt100_read_loop.py

Project repository:
https://github.com/ctch3ng/modbus_playground

Note: The repository is a third-party software example, not an official Eletechsup software release. Verify the register map and communication settings against the AMPTI04 manual before using the code in your own system.

6. Typical Applications

Industrial Equipment Monitoring

Monitor temperatures at several points on production machinery, motors, industrial enclosures, or process equipment.

Heating and Thermal Process Control

Measure temperatures in compatible heating systems, ovens, thermal equipment, and industrial process installations operating within the module's specified measurement range.

HVAC and Building Automation

Collect temperature data from multiple locations in heating, ventilation, and air-conditioning systems. A compatible controller can use the readings to support monitoring and temperature-based control.

Industrial Data Acquisition

Integrate four PT100 measurement points into a PLC, HMI, SCADA system, or industrial computer through Modbus RTU.

Laboratory and Test Equipment

Use the module to collect temperature data from multiple measurement points during equipment testing and experimental setups, provided its accuracy and measurement range meet the application's requirements.

Remote Temperature Monitoring

Combine the AMPTI04 with an industrial gateway or computer to log temperature readings and make them available to a local monitoring application or remote supervisory system.

7. Why Choose a Four-Channel PT100 Acquisition Module?

For applications that require several RTD measurement points, a dedicated temperature acquisition module can reduce the engineering work required to design and integrate separate sensor interfaces.

The AMPTI04 combines four PT100 inputs, RS485 communication, Modbus RTU compatibility, and a DIN-rail installation format in one device.

Its standard communication interface also allows temperature data to be incorporated into existing automation architectures, helping developers build monitoring systems without relying on a proprietary communication protocol.

For applications requiring more measurement points, users can also explore other Eletechsup PT100 acquisition products, including the PTA8E16 16-channel temperature collector.

8. Installation and Design Considerations

PT100 wiring: Follow the manufacturer's terminal diagram for 2-wire or 3-wire sensor connections. Three-wire configurations can help compensate for lead resistance when supported and wired correctly.

Sensor selection: Select PT100 probes with suitable temperature ratings, probe construction, and response characteristics for the target environment.

RS485 communication: Ensure that the master and slave use matching serial parameters and Modbus addresses. Use appropriate cabling, grounding, and termination where required.

Electrical isolation: Follow the manufacturer's installation instructions for power supply, communication wiring, and grounding. Isolation ratings do not eliminate the need for appropriate electrical protection.

Accuracy and calibration: The overall system accuracy depends on the module, PT100 sensor, wiring, installation, and calibration. Confirm the measurement uncertainty required for your application before deployment.

Industrial testing: Test sensor disconnection, communication errors, and temperature readings under representative operating conditions before using the module in critical systems.

9. Conclusion

The Eletechsup AMPTI04 4-Channel PT100 Temperature Acquisition Module provides a practical solution for integrating multiple PT100 temperature sensors into industrial monitoring and automation systems.

With four temperature inputs, RS485 communication, Modbus RTU compatibility, a flexible DC power supply, and DIN-rail installation, it is suitable for a wide range of temperature acquisition and control projects.

The availability of a third-party Python example on GitHub also gives developers a starting point for computer-based testing, data logging, and software integration.

Official product page:
https://eletechsup.com/products/4ch-40-300-celsius-pt100-rtd-temperature-sensor-collector-module-rs485-analog-read-modbus-rtu-plc-expanding-board

GitHub application example:
https://github.com/ctch3ng/modbus_playground/blob/main/ampti04_4ch_pt100_read_loop.py

Eletechsup — Practical Electronic Modules for Industrial Control, Temperature Monitoring, and Automation.

Back to blog

Leave a comment