NTC thermistor

We needed a CAN-bus connected 16-channel temperature sensing interface for a circuit-board functional test application. Specifically to monitor the MOSFET temperatures in the flyback converters of the OGS battery board with active balancers. Not finding such interface, we started designing a quick design to perform this task. This escalated quickly to a real product design; this CANopen® interface for 16 thermistors. Note that this device is not particularly intended for high-accuracy applications, mostly because that does not fit the capabilities of low cost NTC thermistor sensors. Instead, the device enables expanding temperature monitoring using low-cost sensors. For example to monitor motors, bearings, cooling systems, etc. Functionality Measure 16 standard NTC thermistors (typically 10kΩ) Sample rate 100Hz down to 1/60Hz CANopen® fieldbus, generic I/O module profile CiA 401 Modbus RS485 fieldbus Configuration via CANopen or using PC application via micro-USB port Possibility for custom firmware with specific signal processing functions Specifications 24-Bit delta-sigma analog digital converter Autoranging excitation source 10µA-1mA, max 3.3V OLED display shows all 16 temperature readings (°C or °F) Sensor inputs galvanically isolated from CAN-bus (not from each other) CANopen® device profile for generic I/O modules (CiA 401) Supports LSS node-ID assignment and Fastscan (CiA 305) Supports automatic bit-rate detection between 10kbps and 1Mbps (CiA 801) CAN-FD 'Ready' (no active support for FD datarates yet, but tolerates FD traffic on bus)