PT 100 Wireless Logger/Node Design
Budget: $7,500 – $8,000 USD
Revision 3 – 4th August 2025
PT 100 Wireless Data Logger/Node for transmission on LORA 2.4
The purpose of this project is to develop the following, and then we can mass produce for our own use in the future once we have the prototypes working.
To develop a design of a wireless Node that can be deploy in real world, with a max case scenario of 80 nodes intermesh, and transmit a distance of max 300m without LOS to receiving end.
The system uses the AD7124-4 analog-to-digital converter for sensor acquisition, microcontroller control logic, and LoRa 2.4GHz radios for long-range wireless transmission. Intermediate repeater nodes extend signal coverage in distributed environments such as industrial facilities or remote field setups.
Each node in the system will operate in one of the following roles:
Sensor Node: Measures resistance from a 4-wire PT100 RTD and transmits it to a central receiver.
Repeater Node: Relays data from sensor nodes to the receiver to extend communication range.
Things to be provided
1) Customized PCB Design
• Complete schematic and PCB layout, ready for fabrication.
• Include footprint libraries and design files (Gerber, BOM, Pick & Place, Assembly drawings).
Design must integrate:
• 4-wire PT100 RTD input (sensor supplied and calibrated by client)
o High-accuracy ADC/AFE for PT100 (e.g.AD7124-4).
o Suitable MCU for signal processing and LORA 2.4Ghz integration.
o Proper power supply regulation for stable operation.
o All necessary connectors/interfaces.
o Zero and full-scale auto-calibration support
o Built-in data buffering in node in case of network dropouts.
o Antenna for extend range
o Typical input offset: ±25 nV.
o Gain error: ±0.002% of FSR.
o Excellent drift specs: around 1.5 ppm/°C.
o Total system error can stay within or below ±0.05°C(Less RTD)
o Passive Repeat: Store-and-forward LoRa packet
o Active Filtering: Optional ID-based filtering
o Power Source: 12VDC, or AAA or AA batteries
o Auto-routing: Basic RSSI/ACK-based hop decision
Firmware Roles and Functionality
Sensor Node:
• Read resistance via ADC
• Transmit raw resistance data (or calibrated °C)
• Include timestamp, node ID, battery voltage, RSSI, error status
• Buffer at least 10 packets in case of network failure
• Auto calibration before sampling if enabled
• Transmit interval: every 1 minute
Repeater Node:
• Does not read sensor input
• Buffers and relays packets from other nodes
• Optional hop count and signal strength-based routing
• Can be reconfigured to/from sensor mode via software/OTA
Receiver Node:
To receive signals from Sensor or Repeater mode, and transmit to Laptop or PC
2) Complete BOM (Bill of Materials)
• Detailed list of all electronic and mechanical components with part numbers, preferred vendors, and alternatives if applicable.
• Include sourcing recommendations for any difficult-to-source items.
3) Embedded Software/Firmware for Node
• Firmware for the MCU to:
o Read RTD input resistance via ADC.
o Apply calibration coefficients (user-in puttable).
o Convert resistance to temperature using the Callendar–Van Dusen (CVD) equation.
o Package and transmit data wirelessly via LORA 2.4G module.
o Support OTA updates if feasible.
o Self-Calibration process of ADC before logging
o Deployment of wireless nodes
4) PC or Web-Based GUI / Data Logger Software
• Real-time data display for multiple nodes.
• Configurable logging intervals and data storage.
• Visualize live temperature readings.
• Allow input/edit of individual RTD calibration coefficients (A, B, C constants).
• Provide basic export function (CSV or similar).
• To be able to log and perform mathematical functions, like 1 min average, 1 hour average. Linear regression of last 1h(60min valve) of data and etc.
• Timestamping of Data
5) Conversion Functionality
• CVD equation integrated in the firmware and GUI.
• Support for individual calibration curves for each RTD channel.
• UI to upload or edit coefficients.
6) Prototypes: 3 Final Fully Assembled & Working Units
• Fully functional, enclosure optional
• Tested to connect with Laptop
Things to be excluded
1) PT 100 RTDs, we will supply ourself
2) Calibration of the PT 100 RTDs, we will calibrated ourself.
PT 100 Wireless Data Logger/Node for transmission on LORA 2.4
The purpose of this project is to develop the following, and then we can mass produce for our own use in the future once we have the prototypes working.
To develop a design of a wireless Node that can be deploy in real world, with a max case scenario of 80 nodes intermesh, and transmit a distance of max 300m without LOS to receiving end.
The system uses the AD7124-4 analog-to-digital converter for sensor acquisition, microcontroller control logic, and LoRa 2.4GHz radios for long-range wireless transmission. Intermediate repeater nodes extend signal coverage in distributed environments such as industrial facilities or remote field setups.
Each node in the system will operate in one of the following roles:
Sensor Node: Measures resistance from a 4-wire PT100 RTD and transmits it to a central receiver.
Repeater Node: Relays data from sensor nodes to the receiver to extend communication range.
Things to be provided
1) Customized PCB Design
• Complete schematic and PCB layout, ready for fabrication.
• Include footprint libraries and design files (Gerber, BOM, Pick & Place, Assembly drawings).
Design must integrate:
• 4-wire PT100 RTD input (sensor supplied and calibrated by client)
o High-accuracy ADC/AFE for PT100 (e.g.AD7124-4).
o Suitable MCU for signal processing and LORA 2.4Ghz integration.
o Proper power supply regulation for stable operation.
o All necessary connectors/interfaces.
o Zero and full-scale auto-calibration support
o Built-in data buffering in node in case of network dropouts.
o Antenna for extend range
o Typical input offset: ±25 nV.
o Gain error: ±0.002% of FSR.
o Excellent drift specs: around 1.5 ppm/°C.
o Total system error can stay within or below ±0.05°C(Less RTD)
o Passive Repeat: Store-and-forward LoRa packet
o Active Filtering: Optional ID-based filtering
o Power Source: 12VDC, or AAA or AA batteries
o Auto-routing: Basic RSSI/ACK-based hop decision
Firmware Roles and Functionality
Sensor Node:
• Read resistance via ADC
• Transmit raw resistance data (or calibrated °C)
• Include timestamp, node ID, battery voltage, RSSI, error status
• Buffer at least 10 packets in case of network failure
• Auto calibration before sampling if enabled
• Transmit interval: every 1 minute
Repeater Node:
• Does not read sensor input
• Buffers and relays packets from other nodes
• Optional hop count and signal strength-based routing
• Can be reconfigured to/from sensor mode via software/OTA
Receiver Node:
To receive signals from Sensor or Repeater mode, and transmit to Laptop or PC
2) Complete BOM (Bill of Materials)
• Detailed list of all electronic and mechanical components with part numbers, preferred vendors, and alternatives if applicable.
• Include sourcing recommendations for any difficult-to-source items.
3) Embedded Software/Firmware for Node
• Firmware for the MCU to:
o Read RTD input resistance via ADC.
o Apply calibration coefficients (user-in puttable).
o Convert resistance to temperature using the Callendar–Van Dusen (CVD) equation.
o Package and transmit data wirelessly via LORA 2.4G module.
o Support OTA updates if feasible.
o Self-Calibration process of ADC before logging
o Deployment of wireless nodes
4) PC or Web-Based GUI / Data Logger Software
• Real-time data display for multiple nodes.
• Configurable logging intervals and data storage.
• Visualize live temperature readings.
• Allow input/edit of individual RTD calibration coefficients (A, B, C constants).
• Provide basic export function (CSV or similar).
• To be able to log and perform mathematical functions, like 1 min average, 1 hour average. Linear regression of last 1h(60min valve) of data and etc.
• Timestamping of Data
5) Conversion Functionality
• CVD equation integrated in the firmware and GUI.
• Support for individual calibration curves for each RTD channel.
• UI to upload or edit coefficients.
6) Prototypes: 3 Final Fully Assembled & Working Units
• Fully functional, enclosure optional
• Tested to connect with Laptop
Things to be excluded
1) PT 100 RTDs, we will supply ourself
2) Calibration of the PT 100 RTDs, we will calibrated ourself.