How to Design Low-Power Acquisition Circuits for Platinum RTDs?

Low-power temperature acquisition circuits have become a core design requirement for battery-powered wireless sensing, IoT nodes and remote monitoring systems using platinum resistance temperature detectors (RTDs). As a professional expert in precision thermal measurement and low-power analog circuit design, this article introduces the design principles, key component selection and system optimization strategies of ultra-low-power RTD acquisition circuits, focusing on achieving high-precision temperature measurement with supply current below 10 μA, extending battery life and adapting to the long-term operation requirements of the Internet of Things. The core of low-power RTD acquisition circuit design lies in minimizing the power consumption of the entire signal chain while maintaining measurement accuracy and stability. The system adopts a dedicated micro-power constant current source to drive the platinum resistor, avoiding excessive excitation current that causes self-heating error and unnecessary power loss. The constant current source is optimized to operate at sub‑microampere level, ensuring accurate resistance‑temperature conversion without compromising linearity or long‑term drift performance. Signal conditioning uses an ultra-low-power operational amplifier with quiescent current at the nanoampere level, providing high input impedance, low offset voltage and low noise to amplify weak voltage signals from the RTD element. The amplifier is configured to minimize dynamic power consumption while maintaining sufficient bandwidth for stable and accurate sampling. The analog-to-digital conversion stage adopts a low-power high-precision ADC with built-in reference and automatic power-down function, supporting high-resolution sampling at low operating voltage. The ADC operates in intermittent sampling mode to reduce continuous power consumption, and only activates during measurement to complete conversion and data output. A critical power-saving strategy is the implementation of a sleep‑wakeup control mechanism. The circuit remains in deep sleep mode under the control of a microcontroller, with only the real-time clock or wake-up trigger powered on. When a measurement is required, the system quickly powers up the constant current source, op‑amp and ADC, completes sampling and calculation, and immediately returns to sleep mode. This intermittent working mode drastically reduces average power consumption to below 10 μA, making it ideal for coin cell and battery-powered wireless temperature nodes. The entire circuit is designed for wide low-voltage operation, typically from 1.8 V to 3.6 V, compatible with standard battery power systems. PCB layout is optimized to reduce leakage current, noise coupling and parasitic resistance, ensuring measurement accuracy is maintained even under ultra-low power conditions. This low-power acquisition architecture perfectly matches wireless temperature measurement, battery-powered sensors, industrial IoT terminals, agricultural monitoring and indoor environmental sensing applications. It achieves a balance between ultra-low power consumption and high precision, extending battery life to several years without replacement, while ensuring stable, reliable and repeatable temperature data. In summary, low-power RTD acquisition circuits rely on micro-power constant current sources, low-noise low-power op‑amps, low-power ADCs and sleep‑wakeup control to achieve overall supply current below 10 μA. The design supports battery-powered operation, wireless sensing and IoT nodes, enabling long-life, high-precision temperature measurement with minimal energy consumption, and has become a key enabling technology for the development of distributed intelligent sensing systems.